Add dark theme flag

docs/window.dox

@@ -240,7 +240,7 @@ focus when @ref glfwShowWindow is called. Possible values are `GLFW_TRUE` and
 `GLFW_FALSE`.
 
 @anchor GLFW_SCALE_TO_MONITOR
-__GLFW_SCALE_TO_MONITOR__ specified whether the window content area should be
+__GLFW_SCALE_TO_MONITOR__ specifies whether the window content area should be
 resized based on the [monitor content scale](@ref monitor_scale) of any monitor
 it is placed on.  This includes the initial placement when the window is
 created.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.
@@ -249,6 +249,11 @@ This hint only has an effect on platforms where screen coordinates and pixels
 always map 1:1 such as Windows and X11.  On platforms like macOS the resolution
 of the framebuffer is changed independently of the window size.
 
+@anchor GLFW_DARK_THEME
+__GLFW_DARK_THEME__ specifies whether the window should use dark theme or not.
+Possible values are `GLFW_TRUE` and `GLFW_FALSE`. This hint only has effect
+on windows operating system.
+
 @anchor GLFW_MOUSE_PASSTHROUGH_hint
 __GLFW_MOUSE_PASSTHROUGH__ specifies whether the window is transparent to mouse
 input, letting any mouse events pass through to whatever window is behind it.

include/GLFW/glfw3.h

@@ -1099,6 +1099,11 @@ extern "C" {
 /*! @brief macOS specific
  *  [window hint](@ref GLFW_COCOA_RETINA_FRAMEBUFFER_hint).
  */
+#define GLFW_DARK_THEME             0x0002200D
+/*! @brief windows specific
+ *
+ *  Allows specifying whether dark theme should be used.
+ */
 #define GLFW_COCOA_RETINA_FRAMEBUFFER 0x00023001
 /*! @brief macOS specific
  *  [window hint](@ref GLFW_COCOA_FRAME_NAME_hint).

src/internal.h

@@ -408,6 +408,7 @@ struct _GLFWwndconfig
     GLFWbool      focusOnShow;
     GLFWbool      mousePassthrough;
     GLFWbool      scaleToMonitor;
+    GLFWbool      darkTheme;
     struct {
         GLFWbool  retina;
         char      frameName[256];

src/win32_init.c

@@ -151,6 +151,8 @@ static GLFWbool loadLibraries(void)
             _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmEnableBlurBehindWindow");
         _glfw.win32.dwmapi.GetColorizationColor = (PFN_DwmGetColorizationColor)
             _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmGetColorizationColor");
+        _glfw.win32.dwmapi.DwmSetWindowAttribute = (PFN_DwmSetWindowAttribute)
+            _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmSetWindowAttribute");
     }
 
     _glfw.win32.shcore.instance = _glfwPlatformLoadModule("shcore.dll");
@@ -570,6 +572,14 @@ void _glfwUpdateKeyNamesWin32(void)
     }
 }
 
+void _glfwSetWindowTheme(BOOL dark, HWND hwnd)
+{
+#ifndef DWMWA_USE_IMMERSIVE_DARK_MODE
+#define DWMWA_USE_IMMERSIVE_DARK_MODE 20
+#endif
+    _glfw.win32.dwmapi.DwmSetWindowAttribute(hwnd, DWMWA_USE_IMMERSIVE_DARK_MODE, &dark, sizeof(dark));
+}
+
 // Replacement for IsWindowsVersionOrGreater, as we cannot rely on the
 // application having a correct embedded manifest
 //

src/win32_platform.h

@@ -301,6 +301,7 @@ typedef HRESULT (WINAPI * PFN_DwmIsCompositionEnabled)(BOOL*);
 typedef HRESULT (WINAPI * PFN_DwmFlush)(VOID);
 typedef HRESULT (WINAPI * PFN_DwmEnableBlurBehindWindow)(HWND,const DWM_BLURBEHIND*);
 typedef HRESULT (WINAPI * PFN_DwmGetColorizationColor)(DWORD*,BOOL*);
+typedef HRESULT (WINAPI * PFN_DwmSetWindowAttribute)(HWND, DWORD, LPCVOID, DWORD);
 #define DwmIsCompositionEnabled _glfw.win32.dwmapi.IsCompositionEnabled
 #define DwmFlush _glfw.win32.dwmapi.Flush
 #define DwmEnableBlurBehindWindow _glfw.win32.dwmapi.EnableBlurBehindWindow
@@ -487,6 +488,7 @@ typedef struct _GLFWlibraryWin32
         PFN_DwmFlush                    Flush;
         PFN_DwmEnableBlurBehindWindow   EnableBlurBehindWindow;
         PFN_DwmGetColorizationColor     GetColorizationColor;
+        PFN_DwmSetWindowAttribute       DwmSetWindowAttribute;
     } dwmapi;
 
     struct {
@@ -533,6 +535,7 @@ BOOL _glfwIsWindowsVersionOrGreaterWin32(WORD major, WORD minor, WORD sp);
 BOOL _glfwIsWindows10BuildOrGreaterWin32(WORD build);
 void _glfwInputErrorWin32(int error, const char* description);
 void _glfwUpdateKeyNamesWin32(void);
+void _glfwSetWindowTheme(BOOL dark, HWND hwnd);
 
 void _glfwPollMonitorsWin32(void);
 void _glfwSetVideoModeWin32(_GLFWmonitor* monitor, const GLFWvidmode* desired);

src/win32_window.c

@@ -1344,6 +1344,7 @@ static int createNativeWindow(_GLFWwindow* window,
                                            _glfw.win32.instance,
                                            (LPVOID) wndconfig);
 
+    _glfwSetWindowTheme(wndconfig->darkTheme, window->win32.handle);
     _glfw_free(wideTitle);
 
     if (!window->win32.handle)

src/window.c

@@ -388,6 +388,9 @@ GLFWAPI void glfwWindowHint(int hint, int value)
         case GLFW_SCALE_TO_MONITOR:
             _glfw.hints.window.scaleToMonitor = value ? GLFW_TRUE : GLFW_FALSE;
             return;
+        case GLFW_DARK_THEME:
+            _glfw.hints.window.darkTheme = value ? GLFW_TRUE : GLFW_FALSE;
+            return;
         case GLFW_CENTER_CURSOR:
             _glfw.hints.window.centerCursor = value ? GLFW_TRUE : GLFW_FALSE;
             return;