diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 030abf7c..23d1418e 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -137,6 +137,7 @@ video tutorials.
  - Kenneth Miller
  - Bruce Mitchener
  - Jack Moffitt
+ - Ravi Mohan
  - Jeff Molofee
  - Alexander Monakov
  - Pierre Morel
diff --git a/README.md b/README.md
index c3ebd830..fa08b6cb 100644
--- a/README.md
+++ b/README.md
@@ -150,6 +150,7 @@ information on what to include when reporting a bug.
    values to select ANGLE backend (#1380)
  - Added `GLFW_X11_XCB_VULKAN_SURFACE` init hint for selecting X11 Vulkan
    surface extension (#1793)
+ - Added `GLFW_NATIVE_INCLUDE_NONE` for disabling inclusion of native headers (#1348)
  - Added `GLFW_BUILD_WIN32` CMake option for enabling Win32 support (#1958)
  - Added `GLFW_BUILD_COCOA` CMake option for enabling Cocoa support (#1958)
  - Added `GLFW_BUILD_X11` CMake option for enabling X11 support (#1958)
@@ -178,9 +179,11 @@ information on what to include when reporting a bug.
  - Bugfix: Native access functions for context handles did not check that the API matched
  - Bugfix: `glfwMakeContextCurrent` would access TLS slot before initialization
  - Bugfix: `glfwSetGammaRamp` could emit `GLFW_INVALID_VALUE` before initialization
+ - Bugfix: `glfwGetJoystickUserPointer` returned `NULL` during disconnection (#2092)
  - [Win32] Added the `GLFW_WIN32_KEYBOARD_MENU` window hint for enabling access
            to the window menu
  - [Win32] Added a version info resource to the GLFW DLL
+ - [Win32] Made hidden helper window use its own window class
  - [Win32] Disabled framebuffer transparency on Windows 7 when DWM windows are
    opaque (#1512)
  - [Win32] Bugfix: `GLFW_INCLUDE_VULKAN` plus `VK_USE_PLATFORM_WIN32_KHR` caused
@@ -295,6 +298,7 @@ information on what to include when reporting a bug.
  - [X11] Bugfix: Left shift of int constant relied on undefined behavior (#1951)
  - [X11] Bugfix: The OSMesa libray was not unloaded on termination
  - [X11] Bugfix: A malformed response during selection transfer could cause a segfault
+ - [X11] Bugfix: Some calls would reset Xlib to the default error handler (#2108)
  - [Wayland] Added dynamic loading of all Wayland libraries
  - [Wayland] Added support for key names via xkbcommon
  - [Wayland] Added support for file path drop events (#2040)
@@ -330,6 +334,7 @@ information on what to include when reporting a bug.
  - [Wayland] Bugfix: MIME type matching was not performed for clipboard string
  - [Wayland] Bugfix: The OSMesa library was not unloaded on termination
  - [Wayland] Bugfix: `glfwCreateWindow` could emit `GLFW_FEATURE_UNAVAILABLE`
+ - [Wayland] Bugfix: Lock key modifier bits were only set when lock keys were pressed
  - [POSIX] Removed use of deprecated function `gettimeofday`
  - [POSIX] Bugfix: `CLOCK_MONOTONIC` was not correctly tested for or enabled
  - [WGL] Disabled the DWM swap interval hack for Windows 8 and later (#1072)
diff --git a/include/GLFW/glfw3native.h b/include/GLFW/glfw3native.h
index 6d090778..36934120 100644
--- a/include/GLFW/glfw3native.h
+++ b/include/GLFW/glfw3native.h
@@ -74,6 +74,16 @@ extern "C" {
  *  and which platform-specific headers to include.  It is then up your (by
  *  definition platform-specific) code to handle which of these should be
  *  defined.
+ *
+ *  If you do not want the platform-specific headers to be included, define
+ *  `GLFW_NATIVE_INCLUDE_NONE` before including the @ref glfw3native.h header.
+ *
+ *  @code
+ *  #define GLFW_EXPOSE_NATIVE_WIN32
+ *  #define GLFW_EXPOSE_NATIVE_WGL
+ *  #define GLFW_NATIVE_INCLUDE_NONE
+ *  #include <GLFW/glfw3native.h>
+ *  @endcode
  */
 
 
@@ -81,61 +91,65 @@ extern "C" {
  * System headers and types
  *************************************************************************/
 
-#if defined(GLFW_EXPOSE_NATIVE_WIN32) || defined(GLFW_EXPOSE_NATIVE_WGL)
- /* This is a workaround for the fact that glfw3.h needs to export APIENTRY (for
-  * example to allow applications to correctly declare a GL_KHR_debug callback)
-  * but windows.h assumes no one will define APIENTRY before it does
-  */
- #if defined(GLFW_APIENTRY_DEFINED)
-  #undef APIENTRY
-  #undef GLFW_APIENTRY_DEFINED
- #endif
- #include <windows.h>
-#elif defined(GLFW_EXPOSE_NATIVE_COCOA) || defined(GLFW_EXPOSE_NATIVE_NSGL)
- #if defined(__OBJC__)
-  #import <Cocoa/Cocoa.h>
- #else
-  #include <ApplicationServices/ApplicationServices.h>
-  typedef void* id;
- #endif
-#elif defined(GLFW_EXPOSE_NATIVE_X11) || defined(GLFW_EXPOSE_NATIVE_GLX)
- #include <X11/Xlib.h>
- #include <X11/extensions/Xrandr.h>
-#elif defined(GLFW_EXPOSE_NATIVE_WAYLAND)
- #include <wayland-client.h>
-#endif
+#if !defined(GLFW_NATIVE_INCLUDE_NONE)
 
-#if defined(GLFW_EXPOSE_NATIVE_WGL)
- /* WGL is declared by windows.h */
-#endif
-#if defined(GLFW_EXPOSE_NATIVE_NSGL)
- /* NSGL is declared by Cocoa.h */
-#endif
-#if defined(GLFW_EXPOSE_NATIVE_GLX)
- /* This is a workaround for the fact that glfw3.h defines GLAPIENTRY because by
-  * default it also acts as an OpenGL header
-  * However, glx.h will include gl.h, which will define it unconditionally
-  */
- #if defined(GLFW_GLAPIENTRY_DEFINED)
-  #undef GLAPIENTRY
-  #undef GLFW_GLAPIENTRY_DEFINED
+ #if defined(GLFW_EXPOSE_NATIVE_WIN32) || defined(GLFW_EXPOSE_NATIVE_WGL)
+  /* This is a workaround for the fact that glfw3.h needs to export APIENTRY (for
+   * example to allow applications to correctly declare a GL_KHR_debug callback)
+   * but windows.h assumes no one will define APIENTRY before it does
+   */
+  #if defined(GLFW_APIENTRY_DEFINED)
+   #undef APIENTRY
+   #undef GLFW_APIENTRY_DEFINED
+  #endif
+  #include <windows.h>
+ #elif defined(GLFW_EXPOSE_NATIVE_COCOA) || defined(GLFW_EXPOSE_NATIVE_NSGL)
+  #if defined(__OBJC__)
+   #import <Cocoa/Cocoa.h>
+  #else
+   #include <ApplicationServices/ApplicationServices.h>
+   #include <objc/objc.h>
+  #endif
+ #elif defined(GLFW_EXPOSE_NATIVE_X11) || defined(GLFW_EXPOSE_NATIVE_GLX)
+  #include <X11/Xlib.h>
+  #include <X11/extensions/Xrandr.h>
+ #elif defined(GLFW_EXPOSE_NATIVE_WAYLAND)
+  #include <wayland-client.h>
  #endif
- #include <GL/glx.h>
-#endif
-#if defined(GLFW_EXPOSE_NATIVE_EGL)
- #include <EGL/egl.h>
-#endif
-#if defined(GLFW_EXPOSE_NATIVE_OSMESA)
- /* This is a workaround for the fact that glfw3.h defines GLAPIENTRY because by
-  * default it also acts as an OpenGL header
-  * However, osmesa.h will include gl.h, which will define it unconditionally
-  */
- #if defined(GLFW_GLAPIENTRY_DEFINED)
-  #undef GLAPIENTRY
-  #undef GLFW_GLAPIENTRY_DEFINED
+
+ #if defined(GLFW_EXPOSE_NATIVE_WGL)
+  /* WGL is declared by windows.h */
  #endif
- #include <GL/osmesa.h>
-#endif
+ #if defined(GLFW_EXPOSE_NATIVE_NSGL)
+  /* NSGL is declared by Cocoa.h */
+ #endif
+ #if defined(GLFW_EXPOSE_NATIVE_GLX)
+  /* This is a workaround for the fact that glfw3.h defines GLAPIENTRY because by
+   * default it also acts as an OpenGL header
+   * However, glx.h will include gl.h, which will define it unconditionally
+   */
+  #if defined(GLFW_GLAPIENTRY_DEFINED)
+   #undef GLAPIENTRY
+   #undef GLFW_GLAPIENTRY_DEFINED
+  #endif
+  #include <GL/glx.h>
+ #endif
+ #if defined(GLFW_EXPOSE_NATIVE_EGL)
+  #include <EGL/egl.h>
+ #endif
+ #if defined(GLFW_EXPOSE_NATIVE_OSMESA)
+  /* This is a workaround for the fact that glfw3.h defines GLAPIENTRY because by
+   * default it also acts as an OpenGL header
+   * However, osmesa.h will include gl.h, which will define it unconditionally
+   */
+  #if defined(GLFW_GLAPIENTRY_DEFINED)
+   #undef GLAPIENTRY
+   #undef GLFW_GLAPIENTRY_DEFINED
+  #endif
+  #include <GL/osmesa.h>
+ #endif
+
+#endif /*GLFW_NATIVE_INCLUDE_NONE*/
 
 
 /*************************************************************************
diff --git a/src/cocoa_joystick.h b/src/cocoa_joystick.h
index 756911a2..fc7ba7a2 100644
--- a/src/cocoa_joystick.h
+++ b/src/cocoa_joystick.h
@@ -45,7 +45,7 @@ typedef struct _GLFWjoystickNS
 
 GLFWbool _glfwInitJoysticksCocoa(void);
 void _glfwTerminateJoysticksCocoa(void);
-int _glfwPollJoystickCocoa(_GLFWjoystick* js, int mode);
+GLFWbool _glfwPollJoystickCocoa(_GLFWjoystick* js, int mode);
 const char* _glfwGetMappingNameCocoa(void);
 void _glfwUpdateGamepadGUIDCocoa(char* guid);
 
diff --git a/src/cocoa_joystick.m b/src/cocoa_joystick.m
index e09e1efa..ebcf5fdb 100644
--- a/src/cocoa_joystick.m
+++ b/src/cocoa_joystick.m
@@ -96,8 +96,7 @@ static CFComparisonResult compareElements(const void* fp,
 //
 static void closeJoystick(_GLFWjoystick* js)
 {
-    if (!js->present)
-        return;
+    _glfwInputJoystick(js, GLFW_DISCONNECTED);
 
     for (int i = 0;  i < CFArrayGetCount(js->ns.axes);  i++)
         _glfw_free((void*) CFArrayGetValueAtIndex(js->ns.axes, i));
@@ -112,7 +111,6 @@ static void closeJoystick(_GLFWjoystick* js)
     CFRelease(js->ns.hats);
 
     _glfwFreeJoystick(js);
-    _glfwInputJoystick(js, GLFW_DISCONNECTED);
 }
 
 // Callback for user-initiated joystick addition
@@ -289,9 +287,9 @@ static void removeCallback(void* context,
 {
     for (int jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
-        if (_glfw.joysticks[jid].ns.device == device)
+        if (_glfw.joysticks[jid].connected && _glfw.joysticks[jid].ns.device == device)
         {
-            closeJoystick(_glfw.joysticks + jid);
+            closeJoystick(&_glfw.joysticks[jid]);
             break;
         }
     }
@@ -382,7 +380,10 @@ GLFWbool _glfwInitJoysticksCocoa(void)
 void _glfwTerminateJoysticksCocoa(void)
 {
     for (int jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
-        closeJoystick(_glfw.joysticks + jid);
+    {
+        if (_glfw.joysticks[jid].connected)
+            closeJoystick(&_glfw.joysticks[jid]);
+    }
 
     if (_glfw.ns.hidManager)
     {
@@ -392,7 +393,7 @@ void _glfwTerminateJoysticksCocoa(void)
 }
 
 
-int _glfwPollJoystickCocoa(_GLFWjoystick* js, int mode)
+GLFWbool _glfwPollJoystickCocoa(_GLFWjoystick* js, int mode)
 {
     if (mode & _GLFW_POLL_AXES)
     {
@@ -455,7 +456,7 @@ int _glfwPollJoystickCocoa(_GLFWjoystick* js, int mode)
         }
     }
 
-    return js->present;
+    return js->connected;
 }
 
 const char* _glfwGetMappingNameCocoa(void)
diff --git a/src/cocoa_platform.h b/src/cocoa_platform.h
index a22ad7bc..a983297d 100644
--- a/src/cocoa_platform.h
+++ b/src/cocoa_platform.h
@@ -223,7 +223,7 @@ GLFWbool _glfwConnectCocoa(int platformID, _GLFWplatform* platform);
 int _glfwInitCocoa(void);
 void _glfwTerminateCocoa(void);
 
-int _glfwCreateWindowCocoa(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
+GLFWbool _glfwCreateWindowCocoa(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
 void _glfwDestroyWindowCocoa(_GLFWwindow* window);
 void _glfwSetWindowTitleCocoa(_GLFWwindow* window, const char* title);
 void _glfwSetWindowIconCocoa(_GLFWwindow* window, int count, const GLFWimage* images);
@@ -244,12 +244,12 @@ void _glfwHideWindowCocoa(_GLFWwindow* window);
 void _glfwRequestWindowAttentionCocoa(_GLFWwindow* window);
 void _glfwFocusWindowCocoa(_GLFWwindow* window);
 void _glfwSetWindowMonitorCocoa(_GLFWwindow* window, _GLFWmonitor* monitor, int xpos, int ypos, int width, int height, int refreshRate);
-int _glfwWindowFocusedCocoa(_GLFWwindow* window);
-int _glfwWindowIconifiedCocoa(_GLFWwindow* window);
-int _glfwWindowVisibleCocoa(_GLFWwindow* window);
-int _glfwWindowMaximizedCocoa(_GLFWwindow* window);
-int _glfwWindowHoveredCocoa(_GLFWwindow* window);
-int _glfwFramebufferTransparentCocoa(_GLFWwindow* window);
+GLFWbool _glfwWindowFocusedCocoa(_GLFWwindow* window);
+GLFWbool _glfwWindowIconifiedCocoa(_GLFWwindow* window);
+GLFWbool _glfwWindowVisibleCocoa(_GLFWwindow* window);
+GLFWbool _glfwWindowMaximizedCocoa(_GLFWwindow* window);
+GLFWbool _glfwWindowHoveredCocoa(_GLFWwindow* window);
+GLFWbool _glfwFramebufferTransparentCocoa(_GLFWwindow* window);
 void _glfwSetWindowResizableCocoa(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowDecoratedCocoa(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowFloatingCocoa(_GLFWwindow* window, GLFWbool enabled);
@@ -270,8 +270,8 @@ void _glfwSetCursorPosCocoa(_GLFWwindow* window, double xpos, double ypos);
 void _glfwSetCursorModeCocoa(_GLFWwindow* window, int mode);
 const char* _glfwGetScancodeNameCocoa(int scancode);
 int _glfwGetKeyScancodeCocoa(int key);
-int _glfwCreateCursorCocoa(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
-int _glfwCreateStandardCursorCocoa(_GLFWcursor* cursor, int shape);
+GLFWbool _glfwCreateCursorCocoa(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
+GLFWbool _glfwCreateStandardCursorCocoa(_GLFWcursor* cursor, int shape);
 void _glfwDestroyCursorCocoa(_GLFWcursor* cursor);
 void _glfwSetCursorCocoa(_GLFWwindow* window, _GLFWcursor* cursor);
 void _glfwSetClipboardStringCocoa(const char* string);
@@ -282,7 +282,7 @@ EGLNativeDisplayType _glfwGetEGLNativeDisplayCocoa(void);
 EGLNativeWindowType _glfwGetEGLNativeWindowCocoa(_GLFWwindow* window);
 
 void _glfwGetRequiredInstanceExtensionsCocoa(char** extensions);
-int _glfwGetPhysicalDevicePresentationSupportCocoa(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
+GLFWbool _glfwGetPhysicalDevicePresentationSupportCocoa(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
 VkResult _glfwCreateWindowSurfaceCocoa(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
 void _glfwFreeMonitorCocoa(_GLFWmonitor* monitor);
diff --git a/src/cocoa_window.m b/src/cocoa_window.m
index 7248e3e0..16ff46f5 100644
--- a/src/cocoa_window.m
+++ b/src/cocoa_window.m
@@ -893,10 +893,10 @@ float _glfwTransformYCocoa(float y)
 //////                       GLFW platform API                      //////
 //////////////////////////////////////////////////////////////////////////
 
-int _glfwCreateWindowCocoa(_GLFWwindow* window,
-                           const _GLFWwndconfig* wndconfig,
-                           const _GLFWctxconfig* ctxconfig,
-                           const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateWindowCocoa(_GLFWwindow* window,
+                                const _GLFWwndconfig* wndconfig,
+                                const _GLFWctxconfig* ctxconfig,
+                                const _GLFWfbconfig* fbconfig)
 {
     @autoreleasepool {
 
@@ -1309,35 +1309,35 @@ void _glfwSetWindowMonitorCocoa(_GLFWwindow* window,
     } // autoreleasepool
 }
 
-int _glfwWindowFocusedCocoa(_GLFWwindow* window)
+GLFWbool _glfwWindowFocusedCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
     return [window->ns.object isKeyWindow];
     } // autoreleasepool
 }
 
-int _glfwWindowIconifiedCocoa(_GLFWwindow* window)
+GLFWbool _glfwWindowIconifiedCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
     return [window->ns.object isMiniaturized];
     } // autoreleasepool
 }
 
-int _glfwWindowVisibleCocoa(_GLFWwindow* window)
+GLFWbool _glfwWindowVisibleCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
     return [window->ns.object isVisible];
     } // autoreleasepool
 }
 
-int _glfwWindowMaximizedCocoa(_GLFWwindow* window)
+GLFWbool _glfwWindowMaximizedCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
     return [window->ns.object isZoomed];
     } // autoreleasepool
 }
 
-int _glfwWindowHoveredCocoa(_GLFWwindow* window)
+GLFWbool _glfwWindowHoveredCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
 
@@ -1355,7 +1355,7 @@ int _glfwWindowHoveredCocoa(_GLFWwindow* window)
     } // autoreleasepool
 }
 
-int _glfwFramebufferTransparentCocoa(_GLFWwindow* window)
+GLFWbool _glfwFramebufferTransparentCocoa(_GLFWwindow* window)
 {
     @autoreleasepool {
     return ![window->ns.object isOpaque] && ![window->ns.view isOpaque];
@@ -1605,9 +1605,9 @@ int _glfwGetKeyScancodeCocoa(int key)
     return _glfw.ns.scancodes[key];
 }
 
-int _glfwCreateCursorCocoa(_GLFWcursor* cursor,
-                           const GLFWimage* image,
-                           int xhot, int yhot)
+GLFWbool _glfwCreateCursorCocoa(_GLFWcursor* cursor,
+                                const GLFWimage* image,
+                                int xhot, int yhot)
 {
     @autoreleasepool {
 
@@ -1649,7 +1649,7 @@ int _glfwCreateCursorCocoa(_GLFWcursor* cursor,
     } // autoreleasepool
 }
 
-int _glfwCreateStandardCursorCocoa(_GLFWcursor* cursor, int shape)
+GLFWbool _glfwCreateStandardCursorCocoa(_GLFWcursor* cursor, int shape)
 {
     @autoreleasepool {
 
@@ -1832,9 +1832,9 @@ void _glfwGetRequiredInstanceExtensionsCocoa(char** extensions)
     }
 }
 
-int _glfwGetPhysicalDevicePresentationSupportCocoa(VkInstance instance,
-                                                   VkPhysicalDevice device,
-                                                   uint32_t queuefamily)
+GLFWbool _glfwGetPhysicalDevicePresentationSupportCocoa(VkInstance instance,
+                                                        VkPhysicalDevice device,
+                                                        uint32_t queuefamily)
 {
     return GLFW_TRUE;
 }
diff --git a/src/input.c b/src/input.c
index e0a12cce..c2a7a86d 100644
--- a/src/input.c
+++ b/src/input.c
@@ -44,6 +44,13 @@
 #define _GLFW_JOYSTICK_BUTTON   2
 #define _GLFW_JOYSTICK_HATBIT   3
 
+#define GLFW_MOD_MASK (GLFW_MOD_SHIFT | \
+                       GLFW_MOD_CONTROL | \
+                       GLFW_MOD_ALT | \
+                       GLFW_MOD_SUPER | \
+                       GLFW_MOD_CAPS_LOCK | \
+                       GLFW_MOD_NUM_LOCK)
+
 // Initializes the platform joystick API if it has not been already
 //
 static GLFWbool initJoysticks(void)
@@ -266,6 +273,12 @@ static GLFWbool parseMapping(_GLFWmapping* mapping, const char* string)
 //
 void _glfwInputKey(_GLFWwindow* window, int key, int scancode, int action, int mods)
 {
+    assert(window != NULL);
+    assert(key >= 0 || key == GLFW_KEY_UNKNOWN);
+    assert(key <= GLFW_KEY_LAST);
+    assert(action == GLFW_PRESS || action == GLFW_RELEASE);
+    assert(mods == (mods & GLFW_MOD_MASK));
+
     if (key >= 0 && key <= GLFW_KEY_LAST)
     {
         GLFWbool repeated = GLFW_FALSE;
@@ -297,6 +310,10 @@ void _glfwInputKey(_GLFWwindow* window, int key, int scancode, int action, int m
 //
 void _glfwInputChar(_GLFWwindow* window, uint32_t codepoint, int mods, GLFWbool plain)
 {
+    assert(window != NULL);
+    assert(mods == (mods & GLFW_MOD_MASK));
+    assert(plain == GLFW_TRUE || plain == GLFW_FALSE);
+
     if (codepoint < 32 || (codepoint > 126 && codepoint < 160))
         return;
 
@@ -317,6 +334,12 @@ void _glfwInputChar(_GLFWwindow* window, uint32_t codepoint, int mods, GLFWbool
 //
 void _glfwInputScroll(_GLFWwindow* window, double xoffset, double yoffset)
 {
+    assert(window != NULL);
+    assert(xoffset > -FLT_MAX);
+    assert(xoffset < FLT_MAX);
+    assert(yoffset > -FLT_MAX);
+    assert(yoffset < FLT_MAX);
+
     if (window->callbacks.scroll)
         window->callbacks.scroll((GLFWwindow*) window, xoffset, yoffset);
 }
@@ -325,6 +348,12 @@ void _glfwInputScroll(_GLFWwindow* window, double xoffset, double yoffset)
 //
 void _glfwInputMouseClick(_GLFWwindow* window, int button, int action, int mods)
 {
+    assert(window != NULL);
+    assert(button >= 0);
+    assert(button <= GLFW_MOUSE_BUTTON_LAST);
+    assert(action == GLFW_PRESS || action == GLFW_RELEASE);
+    assert(mods == (mods & GLFW_MOD_MASK));
+
     if (button < 0 || button > GLFW_MOUSE_BUTTON_LAST)
         return;
 
@@ -345,6 +374,12 @@ void _glfwInputMouseClick(_GLFWwindow* window, int button, int action, int mods)
 //
 void _glfwInputCursorPos(_GLFWwindow* window, double xpos, double ypos)
 {
+    assert(window != NULL);
+    assert(xpos > -FLT_MAX);
+    assert(xpos < FLT_MAX);
+    assert(ypos > -FLT_MAX);
+    assert(ypos < FLT_MAX);
+
     if (window->virtualCursorPosX == xpos && window->virtualCursorPosY == ypos)
         return;
 
@@ -359,6 +394,9 @@ void _glfwInputCursorPos(_GLFWwindow* window, double xpos, double ypos)
 //
 void _glfwInputCursorEnter(_GLFWwindow* window, GLFWbool entered)
 {
+    assert(window != NULL);
+    assert(entered == GLFW_TRUE || entered == GLFW_FALSE);
+
     if (window->callbacks.cursorEnter)
         window->callbacks.cursorEnter((GLFWwindow*) window, entered);
 }
@@ -367,6 +405,10 @@ void _glfwInputCursorEnter(_GLFWwindow* window, GLFWbool entered)
 //
 void _glfwInputDrop(_GLFWwindow* window, int count, const char** paths)
 {
+    assert(window != NULL);
+    assert(count > 0);
+    assert(paths != NULL);
+
     if (window->callbacks.drop)
         window->callbacks.drop((GLFWwindow*) window, count, paths);
 }
@@ -375,16 +417,26 @@ void _glfwInputDrop(_GLFWwindow* window, int count, const char** paths)
 //
 void _glfwInputJoystick(_GLFWjoystick* js, int event)
 {
-    const int jid = (int) (js - _glfw.joysticks);
+    assert(js != NULL);
+    assert(event == GLFW_CONNECTED || event == GLFW_DISCONNECTED);
+
+    if (event == GLFW_CONNECTED)
+        js->connected = GLFW_TRUE;
+    else if (event == GLFW_DISCONNECTED)
+        js->connected = GLFW_FALSE;
 
     if (_glfw.callbacks.joystick)
-        _glfw.callbacks.joystick(jid, event);
+        _glfw.callbacks.joystick((int) (js - _glfw.joysticks), event);
 }
 
 // Notifies shared code of the new value of a joystick axis
 //
 void _glfwInputJoystickAxis(_GLFWjoystick* js, int axis, float value)
 {
+    assert(js != NULL);
+    assert(axis >= 0);
+    assert(axis < js->axisCount);
+
     js->axes[axis] = value;
 }
 
@@ -392,6 +444,11 @@ void _glfwInputJoystickAxis(_GLFWjoystick* js, int axis, float value)
 //
 void _glfwInputJoystickButton(_GLFWjoystick* js, int button, char value)
 {
+    assert(js != NULL);
+    assert(button >= 0);
+    assert(button < js->buttonCount);
+    assert(value == GLFW_PRESS || value == GLFW_RELEASE);
+
     js->buttons[button] = value;
 }
 
@@ -399,7 +456,18 @@ void _glfwInputJoystickButton(_GLFWjoystick* js, int button, char value)
 //
 void _glfwInputJoystickHat(_GLFWjoystick* js, int hat, char value)
 {
-    const int base = js->buttonCount + hat * 4;
+    int base;
+
+    assert(js != NULL);
+    assert(hat >= 0);
+    assert(hat < js->hatCount);
+
+    // Valid hat values only use the least significant nibble and have at most two bits
+    // set, which can be considered adjacent plus an arbitrary rotation within the nibble
+    assert((value & 0xf0) == 0);
+    assert((value & ((value << 2) | (value >> 2))) == 0);
+
+    base = js->buttonCount + hat * 4;
 
     js->buttons[base + 0] = (value & 0x01) ? GLFW_PRESS : GLFW_RELEASE;
     js->buttons[base + 1] = (value & 0x02) ? GLFW_PRESS : GLFW_RELEASE;
@@ -442,7 +510,7 @@ _GLFWjoystick* _glfwAllocJoystick(const char* name,
 
     for (jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
-        if (!_glfw.joysticks[jid].present)
+        if (!_glfw.joysticks[jid].allocated)
             break;
     }
 
@@ -450,7 +518,7 @@ _GLFWjoystick* _glfwAllocJoystick(const char* name,
         return NULL;
 
     js = _glfw.joysticks + jid;
-    js->present     = GLFW_TRUE;
+    js->allocated   = GLFW_TRUE;
     js->axes        = _glfw_calloc(axisCount, sizeof(float));
     js->buttons     = _glfw_calloc(buttonCount + (size_t) hatCount * 4, 1);
     js->hats        = _glfw_calloc(hatCount, 1);
@@ -972,7 +1040,7 @@ GLFWAPI int glfwJoystickPresent(int jid)
         return GLFW_FALSE;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return GLFW_FALSE;
 
     return _glfw.platform.pollJoystick(js, _GLFW_POLL_PRESENCE);
@@ -1000,7 +1068,7 @@ GLFWAPI const float* glfwGetJoystickAxes(int jid, int* count)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_AXES))
@@ -1032,7 +1100,7 @@ GLFWAPI const unsigned char* glfwGetJoystickButtons(int jid, int* count)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_BUTTONS))
@@ -1068,7 +1136,7 @@ GLFWAPI const unsigned char* glfwGetJoystickHats(int jid, int* count)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_BUTTONS))
@@ -1097,7 +1165,7 @@ GLFWAPI const char* glfwGetJoystickName(int jid)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_PRESENCE))
@@ -1125,7 +1193,7 @@ GLFWAPI const char* glfwGetJoystickGUID(int jid)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_PRESENCE))
@@ -1144,7 +1212,7 @@ GLFWAPI void glfwSetJoystickUserPointer(int jid, void* pointer)
     _GLFW_REQUIRE_INIT();
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->allocated)
         return;
 
     js->userPointer = pointer;
@@ -1160,7 +1228,7 @@ GLFWAPI void* glfwGetJoystickUserPointer(int jid)
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->allocated)
         return NULL;
 
     return js->userPointer;
@@ -1230,7 +1298,7 @@ GLFWAPI int glfwUpdateGamepadMappings(const char* string)
     for (jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
         _GLFWjoystick* js = _glfw.joysticks + jid;
-        if (js->present)
+        if (js->connected)
             js->mapping = findValidMapping(js);
     }
 
@@ -1256,7 +1324,7 @@ GLFWAPI int glfwJoystickIsGamepad(int jid)
         return GLFW_FALSE;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return GLFW_FALSE;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_PRESENCE))
@@ -1284,7 +1352,7 @@ GLFWAPI const char* glfwGetGamepadName(int jid)
         return NULL;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return NULL;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_PRESENCE))
@@ -1319,7 +1387,7 @@ GLFWAPI int glfwGetGamepadState(int jid, GLFWgamepadstate* state)
         return GLFW_FALSE;
 
     js = _glfw.joysticks + jid;
-    if (!js->present)
+    if (!js->connected)
         return GLFW_FALSE;
 
     if (!_glfw.platform.pollJoystick(js, _GLFW_POLL_ALL))
diff --git a/src/internal.h b/src/internal.h
index f6345e12..444aab67 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -665,7 +665,8 @@ struct _GLFWmapping
 //
 struct _GLFWjoystick
 {
-    GLFWbool        present;
+    GLFWbool        allocated;
+    GLFWbool        connected;
     float*          axes;
     int             axisCount;
     unsigned char*  buttons;
@@ -711,8 +712,8 @@ struct _GLFWplatform
     void (*setCursorMode)(_GLFWwindow*,int);
     void (*setRawMouseMotion)(_GLFWwindow*,GLFWbool);
     GLFWbool (*rawMouseMotionSupported)(void);
-    int (*createCursor)(_GLFWcursor*,const GLFWimage*,int,int);
-    int (*createStandardCursor)(_GLFWcursor*,int);
+    GLFWbool (*createCursor)(_GLFWcursor*,const GLFWimage*,int,int);
+    GLFWbool (*createStandardCursor)(_GLFWcursor*,int);
     void (*destroyCursor)(_GLFWcursor*);
     void (*setCursor)(_GLFWwindow*,_GLFWcursor*);
     const char* (*getScancodeName)(int);
@@ -721,7 +722,7 @@ struct _GLFWplatform
     const char* (*getClipboardString)(void);
     GLFWbool (*initJoysticks)(void);
     void (*terminateJoysticks)(void);
-    int (*pollJoystick)(_GLFWjoystick*,int);
+    GLFWbool (*pollJoystick)(_GLFWjoystick*,int);
     const char* (*getMappingName)(void);
     void (*updateGamepadGUID)(char*);
     // monitor
@@ -734,7 +735,7 @@ struct _GLFWplatform
     GLFWbool (*getGammaRamp)(_GLFWmonitor*,GLFWgammaramp*);
     void (*setGammaRamp)(_GLFWmonitor*,const GLFWgammaramp*);
     // window
-    int (*createWindow)(_GLFWwindow*,const _GLFWwndconfig*,const _GLFWctxconfig*,const _GLFWfbconfig*);
+    GLFWbool (*createWindow)(_GLFWwindow*,const _GLFWwndconfig*,const _GLFWctxconfig*,const _GLFWfbconfig*);
     void (*destroyWindow)(_GLFWwindow*);
     void (*setWindowTitle)(_GLFWwindow*,const char*);
     void (*setWindowIcon)(_GLFWwindow*,int,const GLFWimage*);
@@ -755,12 +756,12 @@ struct _GLFWplatform
     void (*requestWindowAttention)(_GLFWwindow*);
     void (*focusWindow)(_GLFWwindow*);
     void (*setWindowMonitor)(_GLFWwindow*,_GLFWmonitor*,int,int,int,int,int);
-    int (*windowFocused)(_GLFWwindow*);
-    int (*windowIconified)(_GLFWwindow*);
-    int (*windowVisible)(_GLFWwindow*);
-    int (*windowMaximized)(_GLFWwindow*);
-    int (*windowHovered)(_GLFWwindow*);
-    int (*framebufferTransparent)(_GLFWwindow*);
+    GLFWbool (*windowFocused)(_GLFWwindow*);
+    GLFWbool (*windowIconified)(_GLFWwindow*);
+    GLFWbool (*windowVisible)(_GLFWwindow*);
+    GLFWbool (*windowMaximized)(_GLFWwindow*);
+    GLFWbool (*windowHovered)(_GLFWwindow*);
+    GLFWbool (*framebufferTransparent)(_GLFWwindow*);
     float (*getWindowOpacity)(_GLFWwindow*);
     void (*setWindowResizable)(_GLFWwindow*,GLFWbool);
     void (*setWindowDecorated)(_GLFWwindow*,GLFWbool);
@@ -778,7 +779,7 @@ struct _GLFWplatform
     EGLNativeWindowType (*getEGLNativeWindow)(_GLFWwindow*);
     // vulkan
     void (*getRequiredInstanceExtensions)(char**);
-    int (*getPhysicalDevicePresentationSupport)(VkInstance,VkPhysicalDevice,uint32_t);
+    GLFWbool (*getPhysicalDevicePresentationSupport)(VkInstance,VkPhysicalDevice,uint32_t);
     VkResult (*createWindowSurface)(VkInstance,_GLFWwindow*,const VkAllocationCallbacks*,VkSurfaceKHR*);
 };
 
diff --git a/src/linux_joystick.c b/src/linux_joystick.c
index da04e9c3..b8b5778e 100644
--- a/src/linux_joystick.c
+++ b/src/linux_joystick.c
@@ -128,7 +128,7 @@ static GLFWbool openJoystickDevice(const char* path)
 {
     for (int jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
-        if (!_glfw.joysticks[jid].present)
+        if (_glfw.joysticks[jid].connected)
             continue;
         if (strcmp(_glfw.joysticks[jid].linjs.path, path) == 0)
             return GLFW_FALSE;
@@ -245,9 +245,9 @@ static GLFWbool openJoystickDevice(const char* path)
 //
 static void closeJoystick(_GLFWjoystick* js)
 {
+    _glfwInputJoystick(js, GLFW_DISCONNECTED);
     close(js->linjs.fd);
     _glfwFreeJoystick(js);
-    _glfwInputJoystick(js, GLFW_DISCONNECTED);
 }
 
 // Lexically compare joysticks by name; used by qsort
@@ -366,7 +366,7 @@ void _glfwTerminateJoysticksLinux(void)
     for (int jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
         _GLFWjoystick* js = _glfw.joysticks + jid;
-        if (js->present)
+        if (js->connected)
             closeJoystick(js);
     }
 
@@ -380,7 +380,7 @@ void _glfwTerminateJoysticksLinux(void)
     }
 }
 
-int _glfwPollJoystickLinux(_GLFWjoystick* js, int mode)
+GLFWbool _glfwPollJoystickLinux(_GLFWjoystick* js, int mode)
 {
     // Read all queued events (non-blocking)
     for (;;)
@@ -417,7 +417,7 @@ int _glfwPollJoystickLinux(_GLFWjoystick* js, int mode)
             handleAbsEvent(js, e.code, e.value);
     }
 
-    return js->present;
+    return js->connected;
 }
 
 const char* _glfwGetMappingNameLinux(void)
diff --git a/src/linux_joystick.h b/src/linux_joystick.h
index 37e5d1ae..f898b2b9 100644
--- a/src/linux_joystick.h
+++ b/src/linux_joystick.h
@@ -59,7 +59,7 @@ void _glfwDetectJoystickConnectionLinux(void);
 
 GLFWbool _glfwInitJoysticksLinux(void);
 void _glfwTerminateJoysticksLinux(void);
-int _glfwPollJoystickLinux(_GLFWjoystick* js, int mode);
+GLFWbool _glfwPollJoystickLinux(_GLFWjoystick* js, int mode);
 const char* _glfwGetMappingNameLinux(void);
 void _glfwUpdateGamepadGUIDLinux(char* guid);
 
diff --git a/src/monitor.c b/src/monitor.c
index 082140ad..6429493b 100644
--- a/src/monitor.c
+++ b/src/monitor.c
@@ -96,6 +96,10 @@ static GLFWbool refreshVideoModes(_GLFWmonitor* monitor)
 //
 void _glfwInputMonitor(_GLFWmonitor* monitor, int action, int placement)
 {
+    assert(monitor != NULL);
+    assert(action == GLFW_CONNECTED || action == GLFW_DISCONNECTED);
+    assert(placement == _GLFW_INSERT_FIRST || placement == _GLFW_INSERT_LAST);
+
     if (action == GLFW_CONNECTED)
     {
         _glfw.monitorCount++;
@@ -155,6 +159,7 @@ void _glfwInputMonitor(_GLFWmonitor* monitor, int action, int placement)
 //
 void _glfwInputMonitorWindow(_GLFWmonitor* monitor, _GLFWwindow* window)
 {
+    assert(monitor != NULL);
     monitor->window = window;
 }
 
diff --git a/src/null_joystick.c b/src/null_joystick.c
index e2770dd8..1fe50721 100644
--- a/src/null_joystick.c
+++ b/src/null_joystick.c
@@ -42,7 +42,7 @@ void _glfwTerminateJoysticksNull(void)
 {
 }
 
-int _glfwPollJoystickNull(_GLFWjoystick* js, int mode)
+GLFWbool _glfwPollJoystickNull(_GLFWjoystick* js, int mode)
 {
     return GLFW_FALSE;
 }
diff --git a/src/null_joystick.h b/src/null_joystick.h
index ec223ecd..a2199c56 100644
--- a/src/null_joystick.h
+++ b/src/null_joystick.h
@@ -26,7 +26,7 @@
 
 GLFWbool _glfwInitJoysticksNull(void);
 void _glfwTerminateJoysticksNull(void);
-int _glfwPollJoystickNull(_GLFWjoystick* js, int mode);
+GLFWbool _glfwPollJoystickNull(_GLFWjoystick* js, int mode);
 const char* _glfwGetMappingNameNull(void);
 void _glfwUpdateGamepadGUIDNull(char* guid);
 
diff --git a/src/null_platform.h b/src/null_platform.h
index f7a94c0f..8f970ad3 100644
--- a/src/null_platform.h
+++ b/src/null_platform.h
@@ -85,7 +85,7 @@ void _glfwGetVideoModeNull(_GLFWmonitor* monitor, GLFWvidmode* mode);
 GLFWbool _glfwGetGammaRampNull(_GLFWmonitor* monitor, GLFWgammaramp* ramp);
 void _glfwSetGammaRampNull(_GLFWmonitor* monitor, const GLFWgammaramp* ramp);
 
-int _glfwCreateWindowNull(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
+GLFWbool _glfwCreateWindowNull(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
 void _glfwDestroyWindowNull(_GLFWwindow* window);
 void _glfwSetWindowTitleNull(_GLFWwindow* window, const char* title);
 void _glfwSetWindowIconNull(_GLFWwindow* window, int count, const GLFWimage* images);
@@ -102,9 +102,9 @@ void _glfwGetWindowContentScaleNull(_GLFWwindow* window, float* xscale, float* y
 void _glfwIconifyWindowNull(_GLFWwindow* window);
 void _glfwRestoreWindowNull(_GLFWwindow* window);
 void _glfwMaximizeWindowNull(_GLFWwindow* window);
-int _glfwWindowMaximizedNull(_GLFWwindow* window);
-int _glfwWindowHoveredNull(_GLFWwindow* window);
-int _glfwFramebufferTransparentNull(_GLFWwindow* window);
+GLFWbool _glfwWindowMaximizedNull(_GLFWwindow* window);
+GLFWbool _glfwWindowHoveredNull(_GLFWwindow* window);
+GLFWbool _glfwFramebufferTransparentNull(_GLFWwindow* window);
 void _glfwSetWindowResizableNull(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowDecoratedNull(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowFloatingNull(_GLFWwindow* window, GLFWbool enabled);
@@ -118,9 +118,9 @@ void _glfwRequestWindowAttentionNull(_GLFWwindow* window);
 void _glfwRequestWindowAttentionNull(_GLFWwindow* window);
 void _glfwHideWindowNull(_GLFWwindow* window);
 void _glfwFocusWindowNull(_GLFWwindow* window);
-int _glfwWindowFocusedNull(_GLFWwindow* window);
-int _glfwWindowIconifiedNull(_GLFWwindow* window);
-int _glfwWindowVisibleNull(_GLFWwindow* window);
+GLFWbool _glfwWindowFocusedNull(_GLFWwindow* window);
+GLFWbool _glfwWindowIconifiedNull(_GLFWwindow* window);
+GLFWbool _glfwWindowVisibleNull(_GLFWwindow* window);
 void _glfwPollEventsNull(void);
 void _glfwWaitEventsNull(void);
 void _glfwWaitEventsTimeoutNull(double timeout);
@@ -128,8 +128,8 @@ void _glfwPostEmptyEventNull(void);
 void _glfwGetCursorPosNull(_GLFWwindow* window, double* xpos, double* ypos);
 void _glfwSetCursorPosNull(_GLFWwindow* window, double x, double y);
 void _glfwSetCursorModeNull(_GLFWwindow* window, int mode);
-int _glfwCreateCursorNull(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
-int _glfwCreateStandardCursorNull(_GLFWcursor* cursor, int shape);
+GLFWbool _glfwCreateCursorNull(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
+GLFWbool _glfwCreateStandardCursorNull(_GLFWcursor* cursor, int shape);
 void _glfwDestroyCursorNull(_GLFWcursor* cursor);
 void _glfwSetCursorNull(_GLFWwindow* window, _GLFWcursor* cursor);
 void _glfwSetClipboardStringNull(const char* string);
@@ -142,7 +142,7 @@ EGLNativeDisplayType _glfwGetEGLNativeDisplayNull(void);
 EGLNativeWindowType _glfwGetEGLNativeWindowNull(_GLFWwindow* window);
 
 void _glfwGetRequiredInstanceExtensionsNull(char** extensions);
-int _glfwGetPhysicalDevicePresentationSupportNull(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
+GLFWbool _glfwGetPhysicalDevicePresentationSupportNull(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
 VkResult _glfwCreateWindowSurfaceNull(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
 void _glfwPollMonitorsNull(void);
diff --git a/src/null_window.c b/src/null_window.c
index c3f6fcdd..5bee9c32 100644
--- a/src/null_window.c
+++ b/src/null_window.c
@@ -103,10 +103,10 @@ static int createNativeWindow(_GLFWwindow* window,
 //////                       GLFW platform API                      //////
 //////////////////////////////////////////////////////////////////////////
 
-int _glfwCreateWindowNull(_GLFWwindow* window,
-                          const _GLFWwndconfig* wndconfig,
-                          const _GLFWctxconfig* ctxconfig,
-                          const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateWindowNull(_GLFWwindow* window,
+                               const _GLFWwndconfig* wndconfig,
+                               const _GLFWctxconfig* ctxconfig,
+                               const _GLFWfbconfig* fbconfig)
 {
     if (!createNativeWindow(window, wndconfig, fbconfig))
         return GLFW_FALSE;
@@ -362,12 +362,12 @@ void _glfwMaximizeWindowNull(_GLFWwindow* window)
     }
 }
 
-int _glfwWindowMaximizedNull(_GLFWwindow* window)
+GLFWbool _glfwWindowMaximizedNull(_GLFWwindow* window)
 {
     return window->null.maximized;
 }
 
-int _glfwWindowHoveredNull(_GLFWwindow* window)
+GLFWbool _glfwWindowHoveredNull(_GLFWwindow* window)
 {
     return _glfw.null.xcursor >= window->null.xpos &&
            _glfw.null.ycursor >= window->null.ypos &&
@@ -375,7 +375,7 @@ int _glfwWindowHoveredNull(_GLFWwindow* window)
            _glfw.null.ycursor <= window->null.ypos + window->null.height - 1;
 }
 
-int _glfwFramebufferTransparentNull(_GLFWwindow* window)
+GLFWbool _glfwFramebufferTransparentNull(_GLFWwindow* window)
 {
     return window->null.transparent;
 }
@@ -461,17 +461,17 @@ void _glfwFocusWindowNull(_GLFWwindow* window)
     _glfwInputWindowFocus(window, GLFW_TRUE);
 }
 
-int _glfwWindowFocusedNull(_GLFWwindow* window)
+GLFWbool _glfwWindowFocusedNull(_GLFWwindow* window)
 {
     return _glfw.null.focusedWindow == window;
 }
 
-int _glfwWindowIconifiedNull(_GLFWwindow* window)
+GLFWbool _glfwWindowIconifiedNull(_GLFWwindow* window)
 {
     return window->null.iconified;
 }
 
-int _glfwWindowVisibleNull(_GLFWwindow* window)
+GLFWbool _glfwWindowVisibleNull(_GLFWwindow* window)
 {
     return window->null.visible;
 }
@@ -510,14 +510,14 @@ void _glfwSetCursorModeNull(_GLFWwindow* window, int mode)
 {
 }
 
-int _glfwCreateCursorNull(_GLFWcursor* cursor,
-                          const GLFWimage* image,
-                          int xhot, int yhot)
+GLFWbool _glfwCreateCursorNull(_GLFWcursor* cursor,
+                               const GLFWimage* image,
+                               int xhot, int yhot)
 {
     return GLFW_TRUE;
 }
 
-int _glfwCreateStandardCursorNull(_GLFWcursor* cursor, int shape)
+GLFWbool _glfwCreateStandardCursorNull(_GLFWcursor* cursor, int shape)
 {
     return GLFW_TRUE;
 }
@@ -693,9 +693,9 @@ void _glfwGetRequiredInstanceExtensionsNull(char** extensions)
 {
 }
 
-int _glfwGetPhysicalDevicePresentationSupportNull(VkInstance instance,
-                                                  VkPhysicalDevice device,
-                                                  uint32_t queuefamily)
+GLFWbool _glfwGetPhysicalDevicePresentationSupportNull(VkInstance instance,
+                                                       VkPhysicalDevice device,
+                                                       uint32_t queuefamily)
 {
     return GLFW_FALSE;
 }
diff --git a/src/win32_init.c b/src/win32_init.c
index a0958503..d1250f11 100644
--- a/src/win32_init.c
+++ b/src/win32_init.c
@@ -331,15 +331,64 @@ static void createKeyTables(void)
     }
 }
 
+// Window procedure for the hidden helper window
+//
+static LRESULT CALLBACK helperWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+{
+    switch (uMsg)
+    {
+        case WM_DISPLAYCHANGE:
+            _glfwPollMonitorsWin32();
+            break;
+
+        case WM_DEVICECHANGE:
+        {
+            if (!_glfw.joysticksInitialized)
+                break;
+
+            if (wParam == DBT_DEVICEARRIVAL)
+            {
+                DEV_BROADCAST_HDR* dbh = (DEV_BROADCAST_HDR*) lParam;
+                if (dbh && dbh->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE)
+                    _glfwDetectJoystickConnectionWin32();
+            }
+            else if (wParam == DBT_DEVICEREMOVECOMPLETE)
+            {
+                DEV_BROADCAST_HDR* dbh = (DEV_BROADCAST_HDR*) lParam;
+                if (dbh && dbh->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE)
+                    _glfwDetectJoystickDisconnectionWin32();
+            }
+
+            break;
+        }
+    }
+
+    return DefWindowProcW(hWnd, uMsg, wParam, lParam);
+}
+
 // Creates a dummy window for behind-the-scenes work
 //
 static GLFWbool createHelperWindow(void)
 {
     MSG msg;
+    WNDCLASSEXW wc = { sizeof(wc) };
+
+    wc.style         = CS_OWNDC;
+    wc.lpfnWndProc   = (WNDPROC) helperWindowProc;
+    wc.hInstance     = _glfw.win32.instance;
+    wc.lpszClassName = L"GLFW3 Helper";
+
+    _glfw.win32.helperWindowClass = RegisterClassExW(&wc);
+    if (!_glfw.win32.helperWindowClass)
+    {
+        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
+                             "WIn32: Failed to register helper window class");
+        return GLFW_FALSE;
+    }
 
     _glfw.win32.helperWindowHandle =
         CreateWindowExW(WS_EX_OVERLAPPEDWINDOW,
-                        _GLFW_WNDCLASSNAME,
+                        MAKEINTATOM(_glfw.win32.helperWindowClass),
                         L"GLFW message window",
                         WS_CLIPSIBLINGS | WS_CLIPCHILDREN,
                         0, 0, 1, 1,
@@ -648,9 +697,6 @@ int _glfwInitWin32(void)
     else if (IsWindowsVistaOrGreater())
         SetProcessDPIAware();
 
-    if (!_glfwRegisterWindowClassWin32())
-        return GLFW_FALSE;
-
     if (!createHelperWindow())
         return GLFW_FALSE;
 
@@ -665,8 +711,10 @@ void _glfwTerminateWin32(void)
 
     if (_glfw.win32.helperWindowHandle)
         DestroyWindow(_glfw.win32.helperWindowHandle);
-
-    _glfwUnregisterWindowClassWin32();
+    if (_glfw.win32.helperWindowClass)
+        UnregisterClassW(MAKEINTATOM(_glfw.win32.helperWindowClass), _glfw.win32.instance);
+    if (_glfw.win32.mainWindowClass)
+        UnregisterClassW(MAKEINTATOM(_glfw.win32.mainWindowClass), _glfw.win32.instance);
 
     _glfw_free(_glfw.win32.clipboardString);
     _glfw_free(_glfw.win32.rawInput);
diff --git a/src/win32_joystick.c b/src/win32_joystick.c
index 7eb9b203..3a28943b 100644
--- a/src/win32_joystick.c
+++ b/src/win32_joystick.c
@@ -256,6 +256,8 @@ static GLFWbool supportsXInput(const GUID* guid)
 //
 static void closeJoystick(_GLFWjoystick* js)
 {
+    _glfwInputJoystick(js, GLFW_DISCONNECTED);
+
     if (js->win32.device)
     {
         IDirectInputDevice8_Unacquire(js->win32.device);
@@ -263,9 +265,7 @@ static void closeJoystick(_GLFWjoystick* js)
     }
 
     _glfw_free(js->win32.objects);
-
     _glfwFreeJoystick(js);
-    _glfwInputJoystick(js, GLFW_DISCONNECTED);
 }
 
 // DirectInput device object enumeration callback
@@ -357,7 +357,7 @@ static BOOL CALLBACK deviceCallback(const DIDEVICEINSTANCE* di, void* user)
     for (jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
         js = _glfw.joysticks + jid;
-        if (js->present)
+        if (js->connected)
         {
             if (memcmp(&js->win32.guid, &di->guidInstance, sizeof(GUID)) == 0)
                 return DIENUM_CONTINUE;
@@ -508,7 +508,7 @@ void _glfwDetectJoystickConnectionWin32(void)
 
             for (jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
             {
-                if (_glfw.joysticks[jid].present &&
+                if (_glfw.joysticks[jid].connected &&
                     _glfw.joysticks[jid].win32.device == NULL &&
                     _glfw.joysticks[jid].win32.index == index)
                 {
@@ -560,7 +560,7 @@ void _glfwDetectJoystickDisconnectionWin32(void)
     for (jid = 0;  jid <= GLFW_JOYSTICK_LAST;  jid++)
     {
         _GLFWjoystick* js = _glfw.joysticks + jid;
-        if (js->present)
+        if (js->connected)
             _glfwPollJoystickWin32(js, _GLFW_POLL_PRESENCE);
     }
 }
@@ -601,7 +601,7 @@ void _glfwTerminateJoysticksWin32(void)
         IDirectInput8_Release(_glfw.win32.dinput8.api);
 }
 
-int _glfwPollJoystickWin32(_GLFWjoystick* js, int mode)
+GLFWbool _glfwPollJoystickWin32(_GLFWjoystick* js, int mode)
 {
     if (js->win32.device)
     {
diff --git a/src/win32_platform.h b/src/win32_platform.h
index 18ea570e..7561de9f 100644
--- a/src/win32_platform.h
+++ b/src/win32_platform.h
@@ -358,10 +358,6 @@ typedef struct VkWin32SurfaceCreateInfoKHR
 typedef VkResult (APIENTRY *PFN_vkCreateWin32SurfaceKHR)(VkInstance,const VkWin32SurfaceCreateInfoKHR*,const VkAllocationCallbacks*,VkSurfaceKHR*);
 typedef VkBool32 (APIENTRY *PFN_vkGetPhysicalDeviceWin32PresentationSupportKHR)(VkPhysicalDevice,uint32_t);
 
-#if !defined(_GLFW_WNDCLASSNAME)
- #define _GLFW_WNDCLASSNAME L"GLFW30"
-#endif
-
 #define GLFW_WIN32_WINDOW_STATE         _GLFWwindowWin32  win32;
 #define GLFW_WIN32_LIBRARY_WINDOW_STATE _GLFWlibraryWin32 win32;
 #define GLFW_WIN32_MONITOR_STATE        _GLFWmonitorWin32 win32;
@@ -453,6 +449,8 @@ typedef struct _GLFWlibraryWin32
 {
     HINSTANCE           instance;
     HWND                helperWindowHandle;
+    ATOM                helperWindowClass;
+    ATOM                mainWindowClass;
     HDEVNOTIFY          deviceNotificationHandle;
     int                 acquiredMonitorCount;
     char*               clipboardString;
@@ -536,9 +534,6 @@ GLFWbool _glfwConnectWin32(int platformID, _GLFWplatform* platform);
 int _glfwInitWin32(void);
 void _glfwTerminateWin32(void);
 
-GLFWbool _glfwRegisterWindowClassWin32(void);
-void _glfwUnregisterWindowClassWin32(void);
-
 WCHAR* _glfwCreateWideStringFromUTF8Win32(const char* source);
 char* _glfwCreateUTF8FromWideStringWin32(const WCHAR* source);
 BOOL _glfwIsWindowsVersionOrGreaterWin32(WORD major, WORD minor, WORD sp);
@@ -551,7 +546,7 @@ void _glfwSetVideoModeWin32(_GLFWmonitor* monitor, const GLFWvidmode* desired);
 void _glfwRestoreVideoModeWin32(_GLFWmonitor* monitor);
 void _glfwGetHMONITORContentScaleWin32(HMONITOR handle, float* xscale, float* yscale);
 
-int _glfwCreateWindowWin32(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
+GLFWbool _glfwCreateWindowWin32(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
 void _glfwDestroyWindowWin32(_GLFWwindow* window);
 void _glfwSetWindowTitleWin32(_GLFWwindow* window, const char* title);
 void _glfwSetWindowIconWin32(_GLFWwindow* window, int count, const GLFWimage* images);
@@ -572,12 +567,12 @@ void _glfwHideWindowWin32(_GLFWwindow* window);
 void _glfwRequestWindowAttentionWin32(_GLFWwindow* window);
 void _glfwFocusWindowWin32(_GLFWwindow* window);
 void _glfwSetWindowMonitorWin32(_GLFWwindow* window, _GLFWmonitor* monitor, int xpos, int ypos, int width, int height, int refreshRate);
-int _glfwWindowFocusedWin32(_GLFWwindow* window);
-int _glfwWindowIconifiedWin32(_GLFWwindow* window);
-int _glfwWindowVisibleWin32(_GLFWwindow* window);
-int _glfwWindowMaximizedWin32(_GLFWwindow* window);
-int _glfwWindowHoveredWin32(_GLFWwindow* window);
-int _glfwFramebufferTransparentWin32(_GLFWwindow* window);
+GLFWbool _glfwWindowFocusedWin32(_GLFWwindow* window);
+GLFWbool _glfwWindowIconifiedWin32(_GLFWwindow* window);
+GLFWbool _glfwWindowVisibleWin32(_GLFWwindow* window);
+GLFWbool _glfwWindowMaximizedWin32(_GLFWwindow* window);
+GLFWbool _glfwWindowHoveredWin32(_GLFWwindow* window);
+GLFWbool _glfwFramebufferTransparentWin32(_GLFWwindow* window);
 void _glfwSetWindowResizableWin32(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowDecoratedWin32(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowFloatingWin32(_GLFWwindow* window, GLFWbool enabled);
@@ -598,8 +593,8 @@ void _glfwSetCursorPosWin32(_GLFWwindow* window, double xpos, double ypos);
 void _glfwSetCursorModeWin32(_GLFWwindow* window, int mode);
 const char* _glfwGetScancodeNameWin32(int scancode);
 int _glfwGetKeyScancodeWin32(int key);
-int _glfwCreateCursorWin32(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
-int _glfwCreateStandardCursorWin32(_GLFWcursor* cursor, int shape);
+GLFWbool _glfwCreateCursorWin32(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
+GLFWbool _glfwCreateStandardCursorWin32(_GLFWcursor* cursor, int shape);
 void _glfwDestroyCursorWin32(_GLFWcursor* cursor);
 void _glfwSetCursorWin32(_GLFWwindow* window, _GLFWcursor* cursor);
 void _glfwSetClipboardStringWin32(const char* string);
@@ -610,7 +605,7 @@ EGLNativeDisplayType _glfwGetEGLNativeDisplayWin32(void);
 EGLNativeWindowType _glfwGetEGLNativeWindowWin32(_GLFWwindow* window);
 
 void _glfwGetRequiredInstanceExtensionsWin32(char** extensions);
-int _glfwGetPhysicalDevicePresentationSupportWin32(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
+GLFWbool _glfwGetPhysicalDevicePresentationSupportWin32(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
 VkResult _glfwCreateWindowSurfaceWin32(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
 void _glfwFreeMonitorWin32(_GLFWmonitor* monitor);
@@ -624,7 +619,7 @@ void _glfwSetGammaRampWin32(_GLFWmonitor* monitor, const GLFWgammaramp* ramp);
 
 GLFWbool _glfwInitJoysticksWin32(void);
 void _glfwTerminateJoysticksWin32(void);
-int _glfwPollJoystickWin32(_GLFWjoystick* js, int mode);
+GLFWbool _glfwPollJoystickWin32(_GLFWjoystick* js, int mode);
 const char* _glfwGetMappingNameWin32(void);
 void _glfwUpdateGamepadGUIDWin32(char* guid);
 
diff --git a/src/win32_window.c b/src/win32_window.c
index dbd167d2..6338e3db 100644
--- a/src/win32_window.c
+++ b/src/win32_window.c
@@ -533,59 +533,26 @@ static void maximizeWindowManually(_GLFWwindow* window)
                  SWP_NOACTIVATE | SWP_NOZORDER | SWP_FRAMECHANGED);
 }
 
-// Window callback function (handles window messages)
+// Window procedure for user-created windows
 //
 static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
     _GLFWwindow* window = GetPropW(hWnd, L"GLFW");
     if (!window)
     {
-        // This is the message handling for the hidden helper window
-        // and for a regular window during its initial creation
-
-        switch (uMsg)
+        if (uMsg == WM_NCCREATE)
         {
-            case WM_NCCREATE:
+            if (_glfwIsWindows10Version1607OrGreaterWin32())
             {
-                if (_glfwIsWindows10Version1607OrGreaterWin32())
-                {
-                    const CREATESTRUCTW* cs = (const CREATESTRUCTW*) lParam;
-                    const _GLFWwndconfig* wndconfig = cs->lpCreateParams;
+                const CREATESTRUCTW* cs = (const CREATESTRUCTW*) lParam;
+                const _GLFWwndconfig* wndconfig = cs->lpCreateParams;
 
-                    // On per-monitor DPI aware V1 systems, only enable
-                    // non-client scaling for windows that scale the client area
-                    // We need WM_GETDPISCALEDSIZE from V2 to keep the client
-                    // area static when the non-client area is scaled
-                    if (wndconfig && wndconfig->scaleToMonitor)
-                        EnableNonClientDpiScaling(hWnd);
-                }
-
-                break;
-            }
-
-            case WM_DISPLAYCHANGE:
-                _glfwPollMonitorsWin32();
-                break;
-
-            case WM_DEVICECHANGE:
-            {
-                if (!_glfw.joysticksInitialized)
-                    break;
-
-                if (wParam == DBT_DEVICEARRIVAL)
-                {
-                    DEV_BROADCAST_HDR* dbh = (DEV_BROADCAST_HDR*) lParam;
-                    if (dbh && dbh->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE)
-                        _glfwDetectJoystickConnectionWin32();
-                }
-                else if (wParam == DBT_DEVICEREMOVECOMPLETE)
-                {
-                    DEV_BROADCAST_HDR* dbh = (DEV_BROADCAST_HDR*) lParam;
-                    if (dbh && dbh->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE)
-                        _glfwDetectJoystickDisconnectionWin32();
-                }
-
-                break;
+                // On per-monitor DPI aware V1 systems, only enable
+                // non-client scaling for windows that scale the client area
+                // We need WM_GETDPISCALEDSIZE from V2 to keep the client
+                // area static when the non-client area is scaled
+                if (wndconfig && wndconfig->scaleToMonitor)
+                    EnableNonClientDpiScaling(hWnd);
             }
         }
 
@@ -1282,6 +1249,39 @@ static int createNativeWindow(_GLFWwindow* window,
     DWORD style = getWindowStyle(window);
     DWORD exStyle = getWindowExStyle(window);
 
+    if (!_glfw.win32.mainWindowClass)
+    {
+        WNDCLASSEXW wc = { sizeof(wc) };
+        wc.style         = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
+        wc.lpfnWndProc   = windowProc;
+        wc.hInstance     = _glfw.win32.instance;
+        wc.hCursor       = LoadCursorW(NULL, IDC_ARROW);
+#if defined(_GLFW_WNDCLASSNAME)
+        wc.lpszClassName = _GLFW_WNDCLASSNAME;
+#else
+        wc.lpszClassName = L"GLFW30";
+#endif
+        // Load user-provided icon if available
+        wc.hIcon = LoadImageW(GetModuleHandleW(NULL),
+                              L"GLFW_ICON", IMAGE_ICON,
+                              0, 0, LR_DEFAULTSIZE | LR_SHARED);
+        if (!wc.hIcon)
+        {
+            // No user-provided icon found, load default icon
+            wc.hIcon = LoadImageW(NULL,
+                                  IDI_APPLICATION, IMAGE_ICON,
+                                  0, 0, LR_DEFAULTSIZE | LR_SHARED);
+        }
+
+        _glfw.win32.mainWindowClass = RegisterClassExW(&wc);
+        if (!_glfw.win32.mainWindowClass)
+        {
+            _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
+                                 "Win32: Failed to register window class");
+            return GLFW_FALSE;
+        }
+    }
+
     if (window->monitor)
     {
         MONITORINFO mi = { sizeof(mi) };
@@ -1315,7 +1315,7 @@ static int createNativeWindow(_GLFWwindow* window,
         return GLFW_FALSE;
 
     window->win32.handle = CreateWindowExW(exStyle,
-                                           _GLFW_WNDCLASSNAME,
+                                           MAKEINTATOM(_glfw.win32.mainWindowClass),
                                            wideTitle,
                                            style,
                                            xpos, ypos,
@@ -1420,53 +1420,10 @@ static int createNativeWindow(_GLFWwindow* window,
     return GLFW_TRUE;
 }
 
-// Registers the GLFW window class
-//
-GLFWbool _glfwRegisterWindowClassWin32(void)
-{
-    WNDCLASSEXW wc;
-
-    ZeroMemory(&wc, sizeof(wc));
-    wc.cbSize        = sizeof(wc);
-    wc.style         = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
-    wc.lpfnWndProc   = windowProc;
-    wc.hInstance     = _glfw.win32.instance;
-    wc.hCursor       = LoadCursorW(NULL, IDC_ARROW);
-    wc.lpszClassName = _GLFW_WNDCLASSNAME;
-
-    // Load user-provided icon if available
-    wc.hIcon = LoadImageW(GetModuleHandleW(NULL),
-                          L"GLFW_ICON", IMAGE_ICON,
-                          0, 0, LR_DEFAULTSIZE | LR_SHARED);
-    if (!wc.hIcon)
-    {
-        // No user-provided icon found, load default icon
-        wc.hIcon = LoadImageW(NULL,
-                              IDI_APPLICATION, IMAGE_ICON,
-                              0, 0, LR_DEFAULTSIZE | LR_SHARED);
-    }
-
-    if (!RegisterClassExW(&wc))
-    {
-        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
-                             "Win32: Failed to register window class");
-        return GLFW_FALSE;
-    }
-
-    return GLFW_TRUE;
-}
-
-// Unregisters the GLFW window class
-//
-void _glfwUnregisterWindowClassWin32(void)
-{
-    UnregisterClassW(_GLFW_WNDCLASSNAME, _glfw.win32.instance);
-}
-
-int _glfwCreateWindowWin32(_GLFWwindow* window,
-                           const _GLFWwndconfig* wndconfig,
-                           const _GLFWctxconfig* ctxconfig,
-                           const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateWindowWin32(_GLFWwindow* window,
+                                const _GLFWwndconfig* wndconfig,
+                                const _GLFWctxconfig* ctxconfig,
+                                const _GLFWfbconfig* fbconfig)
 {
     if (!createNativeWindow(window, wndconfig, fbconfig))
         return GLFW_FALSE;
@@ -1900,32 +1857,32 @@ void _glfwSetWindowMonitorWin32(_GLFWwindow* window,
     }
 }
 
-int _glfwWindowFocusedWin32(_GLFWwindow* window)
+GLFWbool _glfwWindowFocusedWin32(_GLFWwindow* window)
 {
     return window->win32.handle == GetActiveWindow();
 }
 
-int _glfwWindowIconifiedWin32(_GLFWwindow* window)
+GLFWbool _glfwWindowIconifiedWin32(_GLFWwindow* window)
 {
     return IsIconic(window->win32.handle);
 }
 
-int _glfwWindowVisibleWin32(_GLFWwindow* window)
+GLFWbool _glfwWindowVisibleWin32(_GLFWwindow* window)
 {
     return IsWindowVisible(window->win32.handle);
 }
 
-int _glfwWindowMaximizedWin32(_GLFWwindow* window)
+GLFWbool _glfwWindowMaximizedWin32(_GLFWwindow* window)
 {
     return IsZoomed(window->win32.handle);
 }
 
-int _glfwWindowHoveredWin32(_GLFWwindow* window)
+GLFWbool _glfwWindowHoveredWin32(_GLFWwindow* window)
 {
     return cursorInContentArea(window);
 }
 
-int _glfwFramebufferTransparentWin32(_GLFWwindow* window)
+GLFWbool _glfwFramebufferTransparentWin32(_GLFWwindow* window)
 {
     BOOL composition, opaque;
     DWORD color;
@@ -2209,9 +2166,9 @@ int _glfwGetKeyScancodeWin32(int key)
     return _glfw.win32.scancodes[key];
 }
 
-int _glfwCreateCursorWin32(_GLFWcursor* cursor,
-                           const GLFWimage* image,
-                           int xhot, int yhot)
+GLFWbool _glfwCreateCursorWin32(_GLFWcursor* cursor,
+                                const GLFWimage* image,
+                                int xhot, int yhot)
 {
     cursor->win32.handle = (HCURSOR) createIcon(image, xhot, yhot, GLFW_FALSE);
     if (!cursor->win32.handle)
@@ -2220,7 +2177,7 @@ int _glfwCreateCursorWin32(_GLFWcursor* cursor,
     return GLFW_TRUE;
 }
 
-int _glfwCreateStandardCursorWin32(_GLFWcursor* cursor, int shape)
+GLFWbool _glfwCreateStandardCursorWin32(_GLFWcursor* cursor, int shape)
 {
     int id = 0;
 
@@ -2428,9 +2385,9 @@ void _glfwGetRequiredInstanceExtensionsWin32(char** extensions)
     extensions[1] = "VK_KHR_win32_surface";
 }
 
-int _glfwGetPhysicalDevicePresentationSupportWin32(VkInstance instance,
-                                                   VkPhysicalDevice device,
-                                                   uint32_t queuefamily)
+GLFWbool _glfwGetPhysicalDevicePresentationSupportWin32(VkInstance instance,
+                                                        VkPhysicalDevice device,
+                                                        uint32_t queuefamily)
 {
     PFN_vkGetPhysicalDeviceWin32PresentationSupportKHR
         vkGetPhysicalDeviceWin32PresentationSupportKHR =
diff --git a/src/window.c b/src/window.c
index 621e2e64..ebbc6dca 100644
--- a/src/window.c
+++ b/src/window.c
@@ -44,6 +44,9 @@
 //
 void _glfwInputWindowFocus(_GLFWwindow* window, GLFWbool focused)
 {
+    assert(window != NULL);
+    assert(focused == GLFW_TRUE || focused == GLFW_FALSE);
+
     if (window->callbacks.focus)
         window->callbacks.focus((GLFWwindow*) window, focused);
 
@@ -73,6 +76,8 @@ void _glfwInputWindowFocus(_GLFWwindow* window, GLFWbool focused)
 //
 void _glfwInputWindowPos(_GLFWwindow* window, int x, int y)
 {
+    assert(window != NULL);
+
     if (window->callbacks.pos)
         window->callbacks.pos((GLFWwindow*) window, x, y);
 }
@@ -82,6 +87,10 @@ void _glfwInputWindowPos(_GLFWwindow* window, int x, int y)
 //
 void _glfwInputWindowSize(_GLFWwindow* window, int width, int height)
 {
+    assert(window != NULL);
+    assert(width >= 0);
+    assert(height >= 0);
+
     if (window->callbacks.size)
         window->callbacks.size((GLFWwindow*) window, width, height);
 }
@@ -90,6 +99,9 @@ void _glfwInputWindowSize(_GLFWwindow* window, int width, int height)
 //
 void _glfwInputWindowIconify(_GLFWwindow* window, GLFWbool iconified)
 {
+    assert(window != NULL);
+    assert(iconified == GLFW_TRUE || iconified == GLFW_FALSE);
+
     if (window->callbacks.iconify)
         window->callbacks.iconify((GLFWwindow*) window, iconified);
 }
@@ -98,6 +110,9 @@ void _glfwInputWindowIconify(_GLFWwindow* window, GLFWbool iconified)
 //
 void _glfwInputWindowMaximize(_GLFWwindow* window, GLFWbool maximized)
 {
+    assert(window != NULL);
+    assert(maximized == GLFW_TRUE || maximized == GLFW_FALSE);
+
     if (window->callbacks.maximize)
         window->callbacks.maximize((GLFWwindow*) window, maximized);
 }
@@ -107,6 +122,10 @@ void _glfwInputWindowMaximize(_GLFWwindow* window, GLFWbool maximized)
 //
 void _glfwInputFramebufferSize(_GLFWwindow* window, int width, int height)
 {
+    assert(window != NULL);
+    assert(width >= 0);
+    assert(height >= 0);
+
     if (window->callbacks.fbsize)
         window->callbacks.fbsize((GLFWwindow*) window, width, height);
 }
@@ -116,6 +135,12 @@ void _glfwInputFramebufferSize(_GLFWwindow* window, int width, int height)
 //
 void _glfwInputWindowContentScale(_GLFWwindow* window, float xscale, float yscale)
 {
+    assert(window != NULL);
+    assert(xscale > 0.f);
+    assert(xscale < FLT_MAX);
+    assert(yscale > 0.f);
+    assert(yscale < FLT_MAX);
+
     if (window->callbacks.scale)
         window->callbacks.scale((GLFWwindow*) window, xscale, yscale);
 }
@@ -124,6 +149,8 @@ void _glfwInputWindowContentScale(_GLFWwindow* window, float xscale, float yscal
 //
 void _glfwInputWindowDamage(_GLFWwindow* window)
 {
+    assert(window != NULL);
+
     if (window->callbacks.refresh)
         window->callbacks.refresh((GLFWwindow*) window);
 }
@@ -132,6 +159,8 @@ void _glfwInputWindowDamage(_GLFWwindow* window)
 //
 void _glfwInputWindowCloseRequest(_GLFWwindow* window)
 {
+    assert(window != NULL);
+
     window->shouldClose = GLFW_TRUE;
 
     if (window->callbacks.close)
@@ -142,6 +171,7 @@ void _glfwInputWindowCloseRequest(_GLFWwindow* window)
 //
 void _glfwInputWindowMonitor(_GLFWwindow* window, _GLFWmonitor* monitor)
 {
+    assert(window != NULL);
     window->monitor = monitor;
 }
 
diff --git a/src/wl_init.c b/src/wl_init.c
index 569ebbc5..2a104066 100644
--- a/src/wl_init.c
+++ b/src/wl_init.c
@@ -598,10 +598,10 @@ int _glfwInitWayland(void)
         _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_state_key_get_syms");
     _glfw.wl.xkb.state_update_mask = (PFN_xkb_state_update_mask)
         _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_state_update_mask");
-    _glfw.wl.xkb.state_serialize_mods = (PFN_xkb_state_serialize_mods)
-        _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_state_serialize_mods");
     _glfw.wl.xkb.state_key_get_layout = (PFN_xkb_state_key_get_layout)
         _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_state_key_get_layout");
+    _glfw.wl.xkb.state_mod_index_is_active = (PFN_xkb_state_mod_index_is_active)
+        _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_state_mod_index_is_active");
     _glfw.wl.xkb.compose_table_new_from_locale = (PFN_xkb_compose_table_new_from_locale)
         _glfwPlatformGetModuleSymbol(_glfw.wl.xkb.handle, "xkb_compose_table_new_from_locale");
     _glfw.wl.xkb.compose_table_unref = (PFN_xkb_compose_table_unref)
diff --git a/src/wl_platform.h b/src/wl_platform.h
index 20156e92..1f6b9276 100644
--- a/src/wl_platform.h
+++ b/src/wl_platform.h
@@ -167,8 +167,8 @@ typedef struct xkb_state* (* PFN_xkb_state_new)(struct xkb_keymap*);
 typedef void (* PFN_xkb_state_unref)(struct xkb_state*);
 typedef int (* PFN_xkb_state_key_get_syms)(struct xkb_state*, xkb_keycode_t, const xkb_keysym_t**);
 typedef enum xkb_state_component (* PFN_xkb_state_update_mask)(struct xkb_state*, xkb_mod_mask_t, xkb_mod_mask_t, xkb_mod_mask_t, xkb_layout_index_t, xkb_layout_index_t, xkb_layout_index_t);
-typedef xkb_mod_mask_t (* PFN_xkb_state_serialize_mods)(struct xkb_state*, enum xkb_state_component);
 typedef xkb_layout_index_t (* PFN_xkb_state_key_get_layout)(struct xkb_state*,xkb_keycode_t);
+typedef int (* PFN_xkb_state_mod_index_is_active)(struct xkb_state*,xkb_mod_index_t,enum xkb_state_component);
 #define xkb_context_new _glfw.wl.xkb.context_new
 #define xkb_context_unref _glfw.wl.xkb.context_unref
 #define xkb_keymap_new_from_string _glfw.wl.xkb.keymap_new_from_string
@@ -180,8 +180,8 @@ typedef xkb_layout_index_t (* PFN_xkb_state_key_get_layout)(struct xkb_state*,xk
 #define xkb_state_unref _glfw.wl.xkb.state_unref
 #define xkb_state_key_get_syms _glfw.wl.xkb.state_key_get_syms
 #define xkb_state_update_mask _glfw.wl.xkb.state_update_mask
-#define xkb_state_serialize_mods _glfw.wl.xkb.state_serialize_mods
 #define xkb_state_key_get_layout _glfw.wl.xkb.state_key_get_layout
+#define xkb_state_mod_index_is_active _glfw.wl.xkb.state_mod_index_is_active
 
 typedef struct xkb_compose_table* (* PFN_xkb_compose_table_new_from_locale)(struct xkb_context*, const char*, enum xkb_compose_compile_flags);
 typedef void (* PFN_xkb_compose_table_unref)(struct xkb_compose_table*);
@@ -334,12 +334,12 @@ typedef struct _GLFWlibraryWayland
 
         struct xkb_compose_state* composeState;
 
-        xkb_mod_mask_t          controlMask;
-        xkb_mod_mask_t          altMask;
-        xkb_mod_mask_t          shiftMask;
-        xkb_mod_mask_t          superMask;
-        xkb_mod_mask_t          capsLockMask;
-        xkb_mod_mask_t          numLockMask;
+        xkb_mod_index_t         controlIndex;
+        xkb_mod_index_t         altIndex;
+        xkb_mod_index_t         shiftIndex;
+        xkb_mod_index_t         superIndex;
+        xkb_mod_index_t         capsLockIndex;
+        xkb_mod_index_t         numLockIndex;
         unsigned int            modifiers;
 
         PFN_xkb_context_new context_new;
@@ -353,8 +353,8 @@ typedef struct _GLFWlibraryWayland
         PFN_xkb_state_unref state_unref;
         PFN_xkb_state_key_get_syms state_key_get_syms;
         PFN_xkb_state_update_mask state_update_mask;
-        PFN_xkb_state_serialize_mods state_serialize_mods;
         PFN_xkb_state_key_get_layout state_key_get_layout;
+        PFN_xkb_state_mod_index_is_active state_mod_index_is_active;
 
         PFN_xkb_compose_table_new_from_locale compose_table_new_from_locale;
         PFN_xkb_compose_table_unref compose_table_unref;
@@ -436,7 +436,7 @@ GLFWbool _glfwConnectWayland(int platformID, _GLFWplatform* platform);
 int _glfwInitWayland(void);
 void _glfwTerminateWayland(void);
 
-int _glfwCreateWindowWayland(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
+GLFWbool _glfwCreateWindowWayland(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
 void _glfwDestroyWindowWayland(_GLFWwindow* window);
 void _glfwSetWindowTitleWayland(_GLFWwindow* window, const char* title);
 void _glfwSetWindowIconWayland(_GLFWwindow* window, int count, const GLFWimage* images);
@@ -457,12 +457,12 @@ void _glfwHideWindowWayland(_GLFWwindow* window);
 void _glfwRequestWindowAttentionWayland(_GLFWwindow* window);
 void _glfwFocusWindowWayland(_GLFWwindow* window);
 void _glfwSetWindowMonitorWayland(_GLFWwindow* window, _GLFWmonitor* monitor, int xpos, int ypos, int width, int height, int refreshRate);
-int _glfwWindowFocusedWayland(_GLFWwindow* window);
-int _glfwWindowIconifiedWayland(_GLFWwindow* window);
-int _glfwWindowVisibleWayland(_GLFWwindow* window);
-int _glfwWindowMaximizedWayland(_GLFWwindow* window);
-int _glfwWindowHoveredWayland(_GLFWwindow* window);
-int _glfwFramebufferTransparentWayland(_GLFWwindow* window);
+GLFWbool _glfwWindowFocusedWayland(_GLFWwindow* window);
+GLFWbool _glfwWindowIconifiedWayland(_GLFWwindow* window);
+GLFWbool _glfwWindowVisibleWayland(_GLFWwindow* window);
+GLFWbool _glfwWindowMaximizedWayland(_GLFWwindow* window);
+GLFWbool _glfwWindowHoveredWayland(_GLFWwindow* window);
+GLFWbool _glfwFramebufferTransparentWayland(_GLFWwindow* window);
 void _glfwSetWindowResizableWayland(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowDecoratedWayland(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowFloatingWayland(_GLFWwindow* window, GLFWbool enabled);
@@ -483,8 +483,8 @@ void _glfwSetCursorPosWayland(_GLFWwindow* window, double xpos, double ypos);
 void _glfwSetCursorModeWayland(_GLFWwindow* window, int mode);
 const char* _glfwGetScancodeNameWayland(int scancode);
 int _glfwGetKeyScancodeWayland(int key);
-int _glfwCreateCursorWayland(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
-int _glfwCreateStandardCursorWayland(_GLFWcursor* cursor, int shape);
+GLFWbool _glfwCreateCursorWayland(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
+GLFWbool _glfwCreateStandardCursorWayland(_GLFWcursor* cursor, int shape);
 void _glfwDestroyCursorWayland(_GLFWcursor* cursor);
 void _glfwSetCursorWayland(_GLFWwindow* window, _GLFWcursor* cursor);
 void _glfwSetClipboardStringWayland(const char* string);
@@ -495,7 +495,7 @@ EGLNativeDisplayType _glfwGetEGLNativeDisplayWayland(void);
 EGLNativeWindowType _glfwGetEGLNativeWindowWayland(_GLFWwindow* window);
 
 void _glfwGetRequiredInstanceExtensionsWayland(char** extensions);
-int _glfwGetPhysicalDevicePresentationSupportWayland(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
+GLFWbool _glfwGetPhysicalDevicePresentationSupportWayland(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
 VkResult _glfwCreateWindowSurfaceWayland(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
 void _glfwFreeMonitorWayland(_GLFWmonitor* monitor);
diff --git a/src/wl_window.c b/src/wl_window.c
index 7a881a09..6dd658dd 100644
--- a/src/wl_window.c
+++ b/src/wl_window.c
@@ -1269,18 +1269,12 @@ static void keyboardHandleKeymap(void* userData,
     _glfw.wl.xkb.keymap = keymap;
     _glfw.wl.xkb.state = state;
 
-    _glfw.wl.xkb.controlMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Control");
-    _glfw.wl.xkb.altMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod1");
-    _glfw.wl.xkb.shiftMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Shift");
-    _glfw.wl.xkb.superMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod4");
-    _glfw.wl.xkb.capsLockMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Lock");
-    _glfw.wl.xkb.numLockMask =
-        1 << xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod2");
+    _glfw.wl.xkb.controlIndex  = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Control");
+    _glfw.wl.xkb.altIndex      = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod1");
+    _glfw.wl.xkb.shiftIndex    = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Shift");
+    _glfw.wl.xkb.superIndex    = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod4");
+    _glfw.wl.xkb.capsLockIndex = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Lock");
+    _glfw.wl.xkb.numLockIndex  = xkb_keymap_mod_get_index(_glfw.wl.xkb.keymap, "Mod2");
 }
 
 static void keyboardHandleEnter(void* userData,
@@ -1434,27 +1428,49 @@ static void keyboardHandleModifiers(void* userData,
                           0,
                           group);
 
-    const xkb_mod_mask_t mask =
-        xkb_state_serialize_mods(_glfw.wl.xkb.state,
-                                 XKB_STATE_MODS_DEPRESSED |
-                                 XKB_STATE_LAYOUT_DEPRESSED |
-                                 XKB_STATE_MODS_LATCHED |
-                                 XKB_STATE_LAYOUT_LATCHED);
-
     unsigned int mods = 0;
 
-    if (mask & _glfw.wl.xkb.controlMask)
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.controlIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_CONTROL;
-    if (mask & _glfw.wl.xkb.altMask)
+    }
+
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.altIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_ALT;
-    if (mask & _glfw.wl.xkb.shiftMask)
+    }
+
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.shiftIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_SHIFT;
-    if (mask & _glfw.wl.xkb.superMask)
+    }
+
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.superIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_SUPER;
-    if (mask & _glfw.wl.xkb.capsLockMask)
+    }
+
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.capsLockIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_CAPS_LOCK;
-    if (mask & _glfw.wl.xkb.numLockMask)
+    }
+
+    if (xkb_state_mod_index_is_active(_glfw.wl.xkb.state,
+                                      _glfw.wl.xkb.numLockIndex,
+                                      XKB_STATE_MODS_EFFECTIVE) == 1)
+    {
         mods |= GLFW_MOD_NUM_LOCK;
+    }
 
     _glfw.wl.xkb.modifiers = mods;
 }
@@ -1705,10 +1721,10 @@ void _glfwAddDataDeviceListenerWayland(struct wl_data_device* device)
 //////                       GLFW platform API                      //////
 //////////////////////////////////////////////////////////////////////////
 
-int _glfwCreateWindowWayland(_GLFWwindow* window,
-                             const _GLFWwndconfig* wndconfig,
-                             const _GLFWctxconfig* ctxconfig,
-                             const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateWindowWayland(_GLFWwindow* window,
+                                  const _GLFWwndconfig* wndconfig,
+                                  const _GLFWctxconfig* ctxconfig,
+                                  const _GLFWfbconfig* fbconfig)
 {
     if (!createSurface(window, wndconfig, fbconfig))
         return GLFW_FALSE;
@@ -1978,34 +1994,34 @@ void _glfwSetWindowMonitorWayland(_GLFWwindow* window,
     _glfwInputWindowMonitor(window, monitor);
 }
 
-int _glfwWindowFocusedWayland(_GLFWwindow* window)
+GLFWbool _glfwWindowFocusedWayland(_GLFWwindow* window)
 {
     return _glfw.wl.keyboardFocus == window;
 }
 
-int _glfwWindowIconifiedWayland(_GLFWwindow* window)
+GLFWbool _glfwWindowIconifiedWayland(_GLFWwindow* window)
 {
     // xdg-shell doesn’t give any way to request whether a surface is
     // iconified.
     return GLFW_FALSE;
 }
 
-int _glfwWindowVisibleWayland(_GLFWwindow* window)
+GLFWbool _glfwWindowVisibleWayland(_GLFWwindow* window)
 {
     return window->wl.visible;
 }
 
-int _glfwWindowMaximizedWayland(_GLFWwindow* window)
+GLFWbool _glfwWindowMaximizedWayland(_GLFWwindow* window)
 {
     return window->wl.maximized;
 }
 
-int _glfwWindowHoveredWayland(_GLFWwindow* window)
+GLFWbool _glfwWindowHoveredWayland(_GLFWwindow* window)
 {
     return window->wl.hovered;
 }
 
-int _glfwFramebufferTransparentWayland(_GLFWwindow* window)
+GLFWbool _glfwFramebufferTransparentWayland(_GLFWwindow* window)
 {
     return window->wl.transparent;
 }
@@ -2177,9 +2193,9 @@ int _glfwGetKeyScancodeWayland(int key)
     return _glfw.wl.scancodes[key];
 }
 
-int _glfwCreateCursorWayland(_GLFWcursor* cursor,
-                             const GLFWimage* image,
-                             int xhot, int yhot)
+GLFWbool _glfwCreateCursorWayland(_GLFWcursor* cursor,
+                                  const GLFWimage* image,
+                                  int xhot, int yhot)
 {
     cursor->wl.buffer = createShmBuffer(image);
     if (!cursor->wl.buffer)
@@ -2192,7 +2208,7 @@ int _glfwCreateCursorWayland(_GLFWcursor* cursor,
     return GLFW_TRUE;
 }
 
-int _glfwCreateStandardCursorWayland(_GLFWcursor* cursor, int shape)
+GLFWbool _glfwCreateStandardCursorWayland(_GLFWcursor* cursor, int shape)
 {
     const char* name = NULL;
 
@@ -2619,9 +2635,9 @@ void _glfwGetRequiredInstanceExtensionsWayland(char** extensions)
     extensions[1] = "VK_KHR_wayland_surface";
 }
 
-int _glfwGetPhysicalDevicePresentationSupportWayland(VkInstance instance,
-                                                     VkPhysicalDevice device,
-                                                     uint32_t queuefamily)
+GLFWbool _glfwGetPhysicalDevicePresentationSupportWayland(VkInstance instance,
+                                                          VkPhysicalDevice device,
+                                                          uint32_t queuefamily)
 {
     PFN_vkGetPhysicalDeviceWaylandPresentationSupportKHR
         vkGetPhysicalDeviceWaylandPresentationSupportKHR =
diff --git a/src/x11_init.c b/src/x11_init.c
index bf390a00..50bec0a7 100644
--- a/src/x11_init.c
+++ b/src/x11_init.c
@@ -37,6 +37,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <assert.h>
 
 
 // Translate the X11 KeySyms for a key to a GLFW key code
@@ -1095,8 +1096,9 @@ static int errorHandler(Display *display, XErrorEvent* event)
 //
 void _glfwGrabErrorHandlerX11(void)
 {
+    assert(_glfw.x11.errorHandler == NULL);
     _glfw.x11.errorCode = Success;
-    XSetErrorHandler(errorHandler);
+    _glfw.x11.errorHandler = XSetErrorHandler(errorHandler);
 }
 
 // Clears the X error handler callback
@@ -1105,7 +1107,8 @@ void _glfwReleaseErrorHandlerX11(void)
 {
     // Synchronize to make sure all commands are processed
     XSync(_glfw.x11.display, False);
-    XSetErrorHandler(NULL);
+    XSetErrorHandler(_glfw.x11.errorHandler);
+    _glfw.x11.errorHandler = NULL;
 }
 
 // Reports the specified error, appending information about the last X error
diff --git a/src/x11_platform.h b/src/x11_platform.h
index 95eeed05..b78dee10 100644
--- a/src/x11_platform.h
+++ b/src/x11_platform.h
@@ -575,6 +575,8 @@ typedef struct _GLFWlibraryX11
     XContext        context;
     // XIM input method
     XIM             im;
+    // The previous X error handler, to be restored later
+    XErrorHandler   errorHandler;
     // Most recent error code received by X error handler
     int             errorCode;
     // Primary selection string (while the primary selection is owned)
@@ -908,7 +910,7 @@ GLFWbool _glfwConnectX11(int platformID, _GLFWplatform* platform);
 int _glfwInitX11(void);
 void _glfwTerminateX11(void);
 
-int _glfwCreateWindowX11(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
+GLFWbool _glfwCreateWindowX11(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, const _GLFWctxconfig* ctxconfig, const _GLFWfbconfig* fbconfig);
 void _glfwDestroyWindowX11(_GLFWwindow* window);
 void _glfwSetWindowTitleX11(_GLFWwindow* window, const char* title);
 void _glfwSetWindowIconX11(_GLFWwindow* window, int count, const GLFWimage* images);
@@ -929,12 +931,12 @@ void _glfwHideWindowX11(_GLFWwindow* window);
 void _glfwRequestWindowAttentionX11(_GLFWwindow* window);
 void _glfwFocusWindowX11(_GLFWwindow* window);
 void _glfwSetWindowMonitorX11(_GLFWwindow* window, _GLFWmonitor* monitor, int xpos, int ypos, int width, int height, int refreshRate);
-int _glfwWindowFocusedX11(_GLFWwindow* window);
-int _glfwWindowIconifiedX11(_GLFWwindow* window);
-int _glfwWindowVisibleX11(_GLFWwindow* window);
-int _glfwWindowMaximizedX11(_GLFWwindow* window);
-int _glfwWindowHoveredX11(_GLFWwindow* window);
-int _glfwFramebufferTransparentX11(_GLFWwindow* window);
+GLFWbool _glfwWindowFocusedX11(_GLFWwindow* window);
+GLFWbool _glfwWindowIconifiedX11(_GLFWwindow* window);
+GLFWbool _glfwWindowVisibleX11(_GLFWwindow* window);
+GLFWbool _glfwWindowMaximizedX11(_GLFWwindow* window);
+GLFWbool _glfwWindowHoveredX11(_GLFWwindow* window);
+GLFWbool _glfwFramebufferTransparentX11(_GLFWwindow* window);
 void _glfwSetWindowResizableX11(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowDecoratedX11(_GLFWwindow* window, GLFWbool enabled);
 void _glfwSetWindowFloatingX11(_GLFWwindow* window, GLFWbool enabled);
@@ -955,8 +957,8 @@ void _glfwSetCursorPosX11(_GLFWwindow* window, double xpos, double ypos);
 void _glfwSetCursorModeX11(_GLFWwindow* window, int mode);
 const char* _glfwGetScancodeNameX11(int scancode);
 int _glfwGetKeyScancodeX11(int key);
-int _glfwCreateCursorX11(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
-int _glfwCreateStandardCursorX11(_GLFWcursor* cursor, int shape);
+GLFWbool _glfwCreateCursorX11(_GLFWcursor* cursor, const GLFWimage* image, int xhot, int yhot);
+GLFWbool _glfwCreateStandardCursorX11(_GLFWcursor* cursor, int shape);
 void _glfwDestroyCursorX11(_GLFWcursor* cursor);
 void _glfwSetCursorX11(_GLFWwindow* window, _GLFWcursor* cursor);
 void _glfwSetClipboardStringX11(const char* string);
@@ -967,7 +969,7 @@ EGLNativeDisplayType _glfwGetEGLNativeDisplayX11(void);
 EGLNativeWindowType _glfwGetEGLNativeWindowX11(_GLFWwindow* window);
 
 void _glfwGetRequiredInstanceExtensionsX11(char** extensions);
-int _glfwGetPhysicalDevicePresentationSupportX11(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
+GLFWbool _glfwGetPhysicalDevicePresentationSupportX11(VkInstance instance, VkPhysicalDevice device, uint32_t queuefamily);
 VkResult _glfwCreateWindowSurfaceX11(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
 void _glfwFreeMonitorX11(_GLFWmonitor* monitor);
diff --git a/src/x11_window.c b/src/x11_window.c
index 698f2786..623d08ef 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -1895,10 +1895,10 @@ void _glfwCreateInputContextX11(_GLFWwindow* window)
 //////                       GLFW platform API                      //////
 //////////////////////////////////////////////////////////////////////////
 
-int _glfwCreateWindowX11(_GLFWwindow* window,
-                         const _GLFWwndconfig* wndconfig,
-                         const _GLFWctxconfig* ctxconfig,
-                         const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateWindowX11(_GLFWwindow* window,
+                              const _GLFWwndconfig* wndconfig,
+                              const _GLFWctxconfig* ctxconfig,
+                              const _GLFWfbconfig* fbconfig)
 {
     Visual* visual = NULL;
     int depth;
@@ -2462,7 +2462,7 @@ void _glfwSetWindowMonitorX11(_GLFWwindow* window,
     XFlush(_glfw.x11.display);
 }
 
-int _glfwWindowFocusedX11(_GLFWwindow* window)
+GLFWbool _glfwWindowFocusedX11(_GLFWwindow* window)
 {
     Window focused;
     int state;
@@ -2471,19 +2471,19 @@ int _glfwWindowFocusedX11(_GLFWwindow* window)
     return window->x11.handle == focused;
 }
 
-int _glfwWindowIconifiedX11(_GLFWwindow* window)
+GLFWbool _glfwWindowIconifiedX11(_GLFWwindow* window)
 {
     return getWindowState(window) == IconicState;
 }
 
-int _glfwWindowVisibleX11(_GLFWwindow* window)
+GLFWbool _glfwWindowVisibleX11(_GLFWwindow* window)
 {
     XWindowAttributes wa;
     XGetWindowAttributes(_glfw.x11.display, window->x11.handle, &wa);
     return wa.map_state == IsViewable;
 }
 
-int _glfwWindowMaximizedX11(_GLFWwindow* window)
+GLFWbool _glfwWindowMaximizedX11(_GLFWwindow* window)
 {
     Atom* states;
     GLFWbool maximized = GLFW_FALSE;
@@ -2517,7 +2517,7 @@ int _glfwWindowMaximizedX11(_GLFWwindow* window)
     return maximized;
 }
 
-int _glfwWindowHoveredX11(_GLFWwindow* window)
+GLFWbool _glfwWindowHoveredX11(_GLFWwindow* window)
 {
     Window w = _glfw.x11.root;
     while (w)
@@ -2545,7 +2545,7 @@ int _glfwWindowHoveredX11(_GLFWwindow* window)
     return GLFW_FALSE;
 }
 
-int _glfwFramebufferTransparentX11(_GLFWwindow* window)
+GLFWbool _glfwFramebufferTransparentX11(_GLFWwindow* window)
 {
     if (!window->x11.transparent)
         return GLFW_FALSE;
@@ -2848,9 +2848,9 @@ int _glfwGetKeyScancodeX11(int key)
     return _glfw.x11.scancodes[key];
 }
 
-int _glfwCreateCursorX11(_GLFWcursor* cursor,
-                         const GLFWimage* image,
-                         int xhot, int yhot)
+GLFWbool _glfwCreateCursorX11(_GLFWcursor* cursor,
+                              const GLFWimage* image,
+                              int xhot, int yhot)
 {
     cursor->x11.handle = _glfwCreateNativeCursorX11(image, xhot, yhot);
     if (!cursor->x11.handle)
@@ -2859,7 +2859,7 @@ int _glfwCreateCursorX11(_GLFWcursor* cursor,
     return GLFW_TRUE;
 }
 
-int _glfwCreateStandardCursorX11(_GLFWcursor* cursor, int shape)
+GLFWbool _glfwCreateStandardCursorX11(_GLFWcursor* cursor, int shape)
 {
     if (_glfw.x11.xcursor.handle)
     {
@@ -3066,9 +3066,9 @@ void _glfwGetRequiredInstanceExtensionsX11(char** extensions)
         extensions[1] = "VK_KHR_xlib_surface";
 }
 
-int _glfwGetPhysicalDevicePresentationSupportX11(VkInstance instance,
-                                                 VkPhysicalDevice device,
-                                                 uint32_t queuefamily)
+GLFWbool _glfwGetPhysicalDevicePresentationSupportX11(VkInstance instance,
+                                                      VkPhysicalDevice device,
+                                                      uint32_t queuefamily)
 {
     VisualID visualID = XVisualIDFromVisual(DefaultVisual(_glfw.x11.display,
                                                           _glfw.x11.screen));