Wayland: Use tags to verify proxy ownership

This is in preparation for adding support for libdecor, which creates
its own proxies on our display.  It will likely also be helpful to some
people using native access on Wayland.

This is partly based on the implementation of libdecor support in
PR #1693 by @ christianrauch.

(cherry picked from commit 91c837ace5)

src/wl_init.c

@@ -341,6 +341,8 @@ int _glfwPlatformInit(void)
     _glfw.wl.keyRepeatTimerfd = -1;
     _glfw.wl.cursorTimerfd = -1;
 
+    _glfw.wl.tag = glfwGetVersionString();
+
     _glfw.wl.cursor.handle = _glfw_dlopen("libwayland-cursor.so.0");
     if (!_glfw.wl.cursor.handle)
     {

src/wl_monitor.c

@@ -187,6 +187,7 @@ void _glfwAddOutputWayland(uint32_t name, uint32_t version)
     monitor->wl.output = output;
     monitor->wl.name = name;
 
+    wl_proxy_set_tag((struct wl_proxy*) output, &_glfw.wl.tag);
     wl_output_add_listener(output, &outputListener, monitor);
 }
 

src/wl_platform.h

@@ -257,6 +257,8 @@ typedef struct _GLFWlibraryWayland
     _GLFWwindow*                dragFocus;
     uint32_t                    dragSerial;
 
+    const char*                 tag;
+
     struct wl_cursor_theme*     cursorTheme;
     struct wl_cursor_theme*     cursorThemeHiDPI;
     struct wl_surface*          cursorSurface;

src/wl_window.c

@@ -238,6 +238,7 @@ static void createFallbackDecoration(_GLFWdecorationWayland* decoration,
                                      int width, int height)
 {
     decoration->surface = wl_compositor_create_surface(_glfw.wl.compositor);
+    wl_proxy_set_tag((struct wl_proxy*) decoration->surface, &_glfw.wl.tag);
     decoration->subsurface =
         wl_subcompositor_get_subsurface(_glfw.wl.subcompositor,
                                         decoration->surface, parent);
@@ -410,6 +411,9 @@ static void surfaceHandleEnter(void* userData,
                                struct wl_surface* surface,
                                struct wl_output* output)
 {
+    if (wl_proxy_get_tag((struct wl_proxy*) output) != &_glfw.wl.tag)
+        return;
+
     _GLFWwindow* window = userData;
     _GLFWmonitor* monitor = wl_output_get_user_data(output);
 
@@ -430,6 +434,9 @@ static void surfaceHandleLeave(void* userData,
                                struct wl_surface* surface,
                                struct wl_output* output)
 {
+    if (wl_proxy_get_tag((struct wl_proxy*) output) != &_glfw.wl.tag)
+        return;
+
     _GLFWwindow* window = userData;
     _GLFWmonitor* monitor = wl_output_get_user_data(output);
     GLFWbool found;
@@ -766,6 +773,7 @@ static GLFWbool createNativeSurface(_GLFWwindow* window,
         return GLFW_FALSE;
     }
 
+    wl_proxy_set_tag((struct wl_proxy*) window->wl.surface, &_glfw.wl.tag);
     wl_surface_add_listener(window->wl.surface,
                             &surfaceListener,
                             window);
@@ -1099,6 +1107,9 @@ static void pointerHandleEnter(void* userData,
     if (!surface)
         return;
 
+    if (wl_proxy_get_tag((struct wl_proxy*) surface) != &_glfw.wl.tag)
+        return;
+
     _GLFWdecorationSideWayland focus = mainWindow;
     _GLFWwindow* window = wl_surface_get_user_data(surface);
     if (!window)
@@ -1124,8 +1135,13 @@ static void pointerHandleLeave(void* userData,
                                uint32_t serial,
                                struct wl_surface* surface)
 {
-    _GLFWwindow* window = _glfw.wl.pointerFocus;
+    if (!surface)
+        return;
 
+    if (wl_proxy_get_tag((struct wl_proxy*) surface) != &_glfw.wl.tag)
+        return;
+
+    _GLFWwindow* window = _glfw.wl.pointerFocus;
     if (!window)
         return;
 
@@ -1719,7 +1735,10 @@ static void dataDeviceHandleEnter(void* userData,
             _GLFWwindow* window = NULL;
 
             if (surface)
-                window = wl_surface_get_user_data(surface);
+            {
+                if (wl_proxy_get_tag((struct wl_proxy*) surface) == &_glfw.wl.tag)
+                    window = wl_surface_get_user_data(surface);
+            }
 
             if (window && _glfw.wl.offers[i].text_uri_list)
             {
@@ -1734,6 +1753,9 @@ static void dataDeviceHandleEnter(void* userData,
         }
     }
 
+    if (wl_proxy_get_tag((struct wl_proxy*) surface) != &_glfw.wl.tag)
+        return;
+
     if (_glfw.wl.dragOffer)
         wl_data_offer_accept(offer, serial, "text/uri-list");
     else