Wayland: Don’t reload the cursor on every pointer motion

Previously, any pointer motion in the window decorations when using the
fallback implementation would obtain the wl_cursor again, and do the
attach danse for no benefit.

This will ultimately allow animated cursors to not reset to the first
frame on motion, once these will be implemented.

(cherry picked from commit a9f674e719cd663560418de2a7fa1147ce6c6c9b)

src/wl_init.c

@@ -169,6 +169,7 @@ static void setCursor(_GLFWwindow* window, const char* name)
     wl_surface_damage(surface, 0, 0,
                       image->width, image->height);
     wl_surface_commit(surface);
+    _glfw.wl.cursorPreviousName = name;
 }
 
 static void pointerHandleMotion(void* data,
@@ -178,7 +179,7 @@ static void pointerHandleMotion(void* data,
                                 wl_fixed_t sy)
 {
     _GLFWwindow* window = _glfw.wl.pointerFocus;
-    const char* cursorName;
+    const char* cursorName = NULL;
 
     if (!window)
         return;
@@ -227,7 +228,8 @@ static void pointerHandleMotion(void* data,
         default:
             assert(0);
     }
-    setCursor(window, cursorName);
+    if (_glfw.wl.cursorPreviousName != cursorName)
+        setCursor(window, cursorName);
 }
 
 static void pointerHandleButton(void* data,

src/wl_platform.h

@@ -249,6 +249,7 @@ typedef struct _GLFWlibraryWayland
     struct wl_cursor_theme*     cursorTheme;
     struct wl_cursor_theme*     cursorThemeHiDPI;
     struct wl_surface*          cursorSurface;
+    const char*                 cursorPreviousName;
     int                         cursorTimerfd;
     uint32_t                    serial;