Wayland: Simplify decoration side detection

This commit simplifies the detection of which element of a fallback
decorated window the pointer has entered.  Instead of looping through
the list of windows, the user pointer of fallback decoration surfaces is
set to the GLFW window object.

(cherry picked from commit cd466cf9fd)

src/wl_window.c

@@ -231,13 +231,15 @@ static GLFWbool waitForData(struct pollfd* fds, nfds_t count, double* timeout)
     }
 }
 
-static void createFallbackDecoration(_GLFWdecorationWayland* decoration,
+static void createFallbackDecoration(_GLFWwindow* window,
+                                     _GLFWdecorationWayland* decoration,
                                      struct wl_surface* parent,
                                      struct wl_buffer* buffer,
                                      int x, int y,
                                      int width, int height)
 {
     decoration->surface = wl_compositor_create_surface(_glfw.wl.compositor);
+    wl_surface_set_user_data(decoration->surface, window);
     wl_proxy_set_tag((struct wl_proxy*) decoration->surface, &_glfw.wl.tag);
     decoration->subsurface =
         wl_subcompositor_get_subsurface(_glfw.wl.subcompositor,
@@ -268,19 +270,19 @@ static void createFallbackDecorations(_GLFWwindow* window)
     if (!window->wl.decorations.buffer)
         return;
 
-    createFallbackDecoration(&window->wl.decorations.top, window->wl.surface,
+    createFallbackDecoration(window, &window->wl.decorations.top, window->wl.surface,
                              window->wl.decorations.buffer,
                              0, -GLFW_CAPTION_HEIGHT,
                              window->wl.width, GLFW_CAPTION_HEIGHT);
-    createFallbackDecoration(&window->wl.decorations.left, window->wl.surface,
+    createFallbackDecoration(window, &window->wl.decorations.left, window->wl.surface,
                              window->wl.decorations.buffer,
                              -GLFW_BORDER_SIZE, -GLFW_CAPTION_HEIGHT,
                              GLFW_BORDER_SIZE, window->wl.height + GLFW_CAPTION_HEIGHT);
-    createFallbackDecoration(&window->wl.decorations.right, window->wl.surface,
+    createFallbackDecoration(window, &window->wl.decorations.right, window->wl.surface,
                              window->wl.decorations.buffer,
                              window->wl.width, -GLFW_CAPTION_HEIGHT,
                              GLFW_BORDER_SIZE, window->wl.height + GLFW_CAPTION_HEIGHT);
-    createFallbackDecoration(&window->wl.decorations.bottom, window->wl.surface,
+    createFallbackDecoration(window, &window->wl.decorations.bottom, window->wl.surface,
                              window->wl.decorations.buffer,
                              -GLFW_BORDER_SIZE, window->wl.height,
                              window->wl.width + GLFW_BORDER_SIZE * 2, GLFW_BORDER_SIZE);
@@ -1064,40 +1066,6 @@ static char* readDataOfferAsString(struct wl_data_offer* offer, const char* mime
     return string;
 }
 
-static _GLFWwindow* findWindowFromDecorationSurface(struct wl_surface* surface,
-                                                    _GLFWdecorationSideWayland* which)
-{
-    _GLFWdecorationSideWayland focus;
-    _GLFWwindow* window = _glfw.windowListHead;
-    if (!which)
-        which = &focus;
-    while (window)
-    {
-        if (surface == window->wl.decorations.top.surface)
-        {
-            *which = GLFW_TOP_DECORATION;
-            break;
-        }
-        if (surface == window->wl.decorations.left.surface)
-        {
-            *which = GLFW_LEFT_DECORATION;
-            break;
-        }
-        if (surface == window->wl.decorations.right.surface)
-        {
-            *which = GLFW_RIGHT_DECORATION;
-            break;
-        }
-        if (surface == window->wl.decorations.bottom.surface)
-        {
-            *which = GLFW_BOTTOM_DECORATION;
-            break;
-        }
-        window = window->next;
-    }
-    return window;
-}
-
 static void pointerHandleEnter(void* userData,
                                struct wl_pointer* pointer,
                                uint32_t serial,
@@ -1112,16 +1080,19 @@ static void pointerHandleEnter(void* userData,
     if (wl_proxy_get_tag((struct wl_proxy*) surface) != &_glfw.wl.tag)
         return;
 
-    _GLFWdecorationSideWayland focus = GLFW_MAIN_WINDOW;
     _GLFWwindow* window = wl_surface_get_user_data(surface);
-    if (!window)
-    {
-        window = findWindowFromDecorationSurface(surface, &focus);
-        if (!window)
-            return;
-    }
 
-    window->wl.decorations.focus = focus;
+    if (surface == window->wl.decorations.top.surface)
+        window->wl.decorations.focus = GLFW_TOP_DECORATION;
+    else if (surface == window->wl.decorations.left.surface)
+        window->wl.decorations.focus = GLFW_LEFT_DECORATION;
+    else if (surface == window->wl.decorations.right.surface)
+        window->wl.decorations.focus = GLFW_RIGHT_DECORATION;
+    else if (surface == window->wl.decorations.bottom.surface)
+        window->wl.decorations.focus = GLFW_BOTTOM_DECORATION;
+    else
+        window->wl.decorations.focus = GLFW_MAIN_WINDOW;
+
     _glfw.wl.serial = serial;
     _glfw.wl.pointerEnterSerial = serial;
     _glfw.wl.pointerFocus = window;
@@ -1484,13 +1455,12 @@ static void keyboardHandleEnter(void* userData,
     if (!surface)
         return;
 
+    if (wl_proxy_get_tag((struct wl_proxy*) surface) != &_glfw.wl.tag)
+        return;
+
     _GLFWwindow* window = wl_surface_get_user_data(surface);
-    if (!window)
+    if (surface != window->wl.surface)
-    {
+        return;
-        window = findWindowFromDecorationSurface(surface, NULL);
-        if (!window)
-            return;
-    }
 
     _glfw.wl.serial = serial;
     _glfw.wl.keyboardFocus = window;
@@ -1743,7 +1713,7 @@ static void dataDeviceHandleEnter(void* userData,
                     window = wl_surface_get_user_data(surface);
             }
 
-            if (window && _glfw.wl.offers[i].text_uri_list)
+            if (surface == window->wl.surface && _glfw.wl.offers[i].text_uri_list)
             {
                 _glfw.wl.dragOffer = offer;
                 _glfw.wl.dragFocus = window;