X11: Use XI_RawMotion for disabled cursor motion

Related to #125.

README.md

@@ -168,6 +168,7 @@ information on what to include when reporting a bug.
                   function on macOS 10.12+
 - [Cocoa] Bugfix: Running in AppSandbox would emit warnings (#816,#882)
 - [Cocoa] Bugfix: Windows created after the first were not cascaded (#195)
+- [X11] Moved to XI2 `XI_RawMotion` for disable cursor mode motion input (#125)
 - [EGL] Added support for `EGL_KHR_get_all_proc_addresses` (#871)
 - [EGL] Bugfix: The test for `EGL_RGB_BUFFER` was invalid
 

src/x11_init.c

@@ -477,6 +477,32 @@ static GLFWbool initExtensions(void)
                                       &_glfw.x11.vidmode.errorBase);
     }
 
+    _glfw.x11.xi.handle = dlopen("libXi.so", RTLD_LAZY | RTLD_GLOBAL);
+    if (_glfw.x11.xi.handle)
+    {
+        _glfw.x11.xi.QueryVersion = (PFN_XIQueryVersion)
+            dlsym(_glfw.x11.xi.handle, "XIQueryVersion");
+        _glfw.x11.xi.SelectEvents = (PFN_XISelectEvents)
+            dlsym(_glfw.x11.xi.handle, "XISelectEvents");
+
+        if (XQueryExtension(_glfw.x11.display,
+                            "XInputExtension",
+                            &_glfw.x11.xi.majorOpcode,
+                            &_glfw.x11.xi.eventBase,
+                            &_glfw.x11.xi.errorBase))
+        {
+            _glfw.x11.xi.major = 2;
+            _glfw.x11.xi.minor = 0;
+
+            if (XIQueryVersion(_glfw.x11.display,
+                               &_glfw.x11.xi.major,
+                               &_glfw.x11.xi.minor) == Success)
+            {
+                _glfw.x11.xi.available = GLFW_TRUE;
+            }
+        }
+    }
+
     // Check for RandR extension
     if (XRRQueryExtension(_glfw.x11.display,
                           &_glfw.x11.randr.eventBase,

src/x11_platform.h

@@ -47,6 +47,9 @@
 // The Xinerama extension provides legacy monitor indices
 #include <X11/extensions/Xinerama.h>
 
+// The XInput extension provides raw mouse motion input
+#include <X11/extensions/XInput2.h>
+
 typedef XID xcb_window_t;
 typedef XID xcb_visualid_t;
 typedef struct xcb_connection_t xcb_connection_t;
@@ -61,6 +64,11 @@ typedef Bool (* PFN_XF86VidModeGetGammaRampSize)(Display*,int,int*);
 #define XF86VidModeSetGammaRamp _glfw.x11.vidmode.SetGammaRamp
 #define XF86VidModeGetGammaRampSize _glfw.x11.vidmode.GetGammaRampSize
 
+typedef Status (* PFN_XIQueryVersion)(Display*,int*,int*);
+typedef int (* PFN_XISelectEvents)(Display*,Window,XIEventMask*,int);
+#define XIQueryVersion _glfw.x11.xi.QueryVersion
+#define XISelectEvents _glfw.x11.xi.SelectEvents
+
 typedef VkFlags VkXlibSurfaceCreateFlagsKHR;
 typedef VkFlags VkXcbSurfaceCreateFlagsKHR;
 
@@ -269,6 +277,18 @@ typedef struct _GLFWlibraryX11
         PFN_XF86VidModeGetGammaRampSize GetGammaRampSize;
     } vidmode;
 
+    struct {
+        GLFWbool    available;
+        void*       handle;
+        int         majorOpcode;
+        int         eventBase;
+        int         errorBase;
+        int         major;
+        int         minor;
+        PFN_XIQueryVersion QueryVersion;
+        PFN_XISelectEvents SelectEvents;
+    } xi;
+
 } _GLFWlibraryX11;
 
 // X11-specific per-monitor data

src/x11_window.c

@@ -920,14 +920,48 @@ static void processEvent(XEvent *event)
         }
     }
 
-    if (event->type != GenericEvent)
+    if (event->type == GenericEvent)
     {
-        window = findWindowByHandle(event->xany.window);
-        if (window == NULL)
+        if (_glfw.x11.xi.available)
         {
-            // This is an event for a window that has already been destroyed
-            return;
+            _GLFWwindow* window = _glfw.x11.disabledCursorWindow;
+
+            if (window &&
+                event->xcookie.extension == _glfw.x11.xi.majorOpcode &&
+                XGetEventData(_glfw.x11.display, &event->xcookie) &&
+                event->xcookie.evtype == XI_RawMotion)
+            {
+                XIRawEvent* re = event->xcookie.data;
+                if (re->valuators.mask_len)
+                {
+                    const double* values = re->raw_values;
+                    double xpos = window->virtualCursorPosX;
+                    double ypos = window->virtualCursorPosY;
+
+                    if (XIMaskIsSet(re->valuators.mask, 0))
+                    {
+                        xpos += *values;
+                        values++;
+                    }
+
+                    if (XIMaskIsSet(re->valuators.mask, 1))
+                        ypos += *values;
+
+                    _glfwInputCursorPos(window, xpos, ypos);
+                }
+            }
+
+            XFreeEventData(_glfw.x11.display, &event->xcookie);
         }
+
+        return;
+    }
+
+    window = findWindowByHandle(event->xany.window);
+    if (window == NULL)
+    {
+        // This is an event for a window that has already been destroyed
+        return;
     }
 
     switch (event->type)
@@ -1170,6 +1204,8 @@ static void processEvent(XEvent *event)
                 {
                     if (_glfw.x11.disabledCursorWindow != window)
                         return;
+                    if (_glfw.x11.xi.available)
+                        return;
 
                     const int dx = x - window->x11.lastCursorPosX;
                     const int dy = y - window->x11.lastCursorPosY;
@@ -2157,6 +2193,8 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
 
 void _glfwPlatformPollEvents(void)
 {
+    _GLFWwindow* window;
+
 #if defined(__linux__)
     _glfwDetectJoystickConnectionLinux();
 #endif
@@ -2168,8 +2206,20 @@ void _glfwPlatformPollEvents(void)
         processEvent(&event);
     }
 
-    if (_glfw.x11.disabledCursorWindow)
-        centerCursor(_glfw.x11.disabledCursorWindow);
+    window = _glfw.x11.disabledCursorWindow;
+    if (window)
+    {
+        int width, height;
+        _glfwPlatformGetWindowSize(window, &width, &height);
+
+        // NOTE: Re-center the cursor only if it has moved since the last call,
+        //       to avoid breaking glfwWaitEvents with MotionNotify
+        if (window->x11.lastCursorPosX != width / 2 ||
+            window->x11.lastCursorPosY != height / 2)
+        {
+            _glfwPlatformSetCursorPos(window, width / 2, height / 2);
+        }
+    }
 
     XFlush(_glfw.x11.display);
 }
@@ -2239,6 +2289,19 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
 {
     if (mode == GLFW_CURSOR_DISABLED)
     {
+        if (_glfw.x11.xi.available)
+        {
+            XIEventMask em;
+            unsigned char mask[XIMaskLen(XI_RawMotion)] = { 0 };
+
+            em.deviceid = XIAllMasterDevices;
+            em.mask_len = sizeof(mask);
+            em.mask = mask;
+            XISetMask(mask, XI_RawMotion);
+
+            XISelectEvents(_glfw.x11.display, _glfw.x11.root, &em, 1);
+        }
+
         _glfw.x11.disabledCursorWindow = window;
         _glfwPlatformGetCursorPos(window,
                                   &_glfw.x11.restoreCursorPosX,
@@ -2253,6 +2316,18 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
     }
     else if (_glfw.x11.disabledCursorWindow == window)
     {
+        if (_glfw.x11.xi.available)
+        {
+            XIEventMask em;
+            unsigned char mask[] = { 0 };
+
+            em.deviceid = XIAllMasterDevices;
+            em.mask_len = sizeof(mask);
+            em.mask = mask;
+
+            XISelectEvents(_glfw.x11.display, _glfw.x11.root, &em, 1);
+        }
+
         _glfw.x11.disabledCursorWindow = NULL;
         XUngrabPointer(_glfw.x11.display, CurrentTime);
         _glfwPlatformSetCursorPos(window,