Set decorations as opaque, to optimise composition

src/wl_window.c

@@ -224,9 +224,12 @@ static struct wl_buffer* createShmBuffer(const GLFWimage* image)
 
 static void createDecoration(_GLFWdecorationWayland* decoration,
                              struct wl_surface* parent,
-                             struct wl_buffer* buffer, int x, int y,
+                             struct wl_buffer* buffer, GLFWbool opaque,
+                             int x, int y,
                              int width, int height)
 {
+    struct wl_region* region;
+
     decoration->surface = wl_compositor_create_surface(_glfw.wl.compositor);
     decoration->subsurface =
         wl_subcompositor_get_subsurface(_glfw.wl.subcompositor,
@@ -236,13 +239,24 @@ static void createDecoration(_GLFWdecorationWayland* decoration,
                                                       decoration->surface);
     wp_viewport_set_destination(decoration->viewport, width, height);
     wl_surface_attach(decoration->surface, buffer, 0, 0);
-    wl_surface_commit(decoration->surface);
+
+    if (opaque)
+    {
+        region = wl_compositor_create_region(_glfw.wl.compositor);
+        wl_region_add(region, 0, 0, width, height);
+        wl_surface_set_opaque_region(decoration->surface, region);
+        wl_surface_commit(decoration->surface);
+        wl_region_destroy(region);
+    }
+    else
+        wl_surface_commit(decoration->surface);
 }
 
 static void createDecorations(_GLFWwindow* window)
 {
     unsigned char data[] = { 224, 224, 224, 255 };
     const GLFWimage image = { 1, 1, data };
+    GLFWbool opaque = (data[3] == 255);
 
     if (!_glfw.wl.viewporter)
         return;
@@ -251,19 +265,19 @@ static void createDecorations(_GLFWwindow* window)
         window->wl.decorations.buffer = createShmBuffer(&image);
 
     createDecoration(&window->wl.decorations.top, window->wl.surface,
-                     window->wl.decorations.buffer,
+                     window->wl.decorations.buffer, opaque,
                      0, -_GLFW_DECORATION_TOP,
                      window->wl.width, _GLFW_DECORATION_TOP);
     createDecoration(&window->wl.decorations.left, window->wl.surface,
-                     window->wl.decorations.buffer,
+                     window->wl.decorations.buffer, opaque,
                      -_GLFW_DECORATION_WIDTH, -_GLFW_DECORATION_TOP,
                      _GLFW_DECORATION_WIDTH, window->wl.height + _GLFW_DECORATION_TOP);
     createDecoration(&window->wl.decorations.right, window->wl.surface,
-                     window->wl.decorations.buffer,
+                     window->wl.decorations.buffer, opaque,
                      window->wl.width, -_GLFW_DECORATION_TOP,
                      _GLFW_DECORATION_WIDTH, window->wl.height + _GLFW_DECORATION_TOP);
     createDecoration(&window->wl.decorations.bottom, window->wl.surface,
-                     window->wl.decorations.buffer,
+                     window->wl.decorations.buffer, opaque,
                      -_GLFW_DECORATION_WIDTH, window->wl.height,
                      window->wl.width + _GLFW_DECORATION_HORIZONTAL, _GLFW_DECORATION_WIDTH);
 }