Moved _NET_REQUEST_FRAME_EXTENTS to frame query.

The request is now only made when necessary and times out after 500ms.
This breaks our end of the protocol to work around broken
implementations at the other end.

It uses the GLFW timer instead of select, as select is not guaranteed to
update the timeout with the time remaining and a single select is not
sufficient as other events may be incoming.

Fixes #368 (mostly).
Fixes #429 (mostly).

README.md

@@ -70,6 +70,9 @@ GLFW bundles a number of dependencies in the `deps/` directory.
  - [X11] Added support for Cygwin-X
  - [X11] Made XInput2 optional at compile-time
  - [X11] Made Xxf86vm optional at compile-time
+ - [X11] Bugfix: Moved `_NET_REQUEST_FRAME_EXTENTS` request to
+                 `glfwGetWindowFrameSize` and added protocol-breaking timeout
+                 as a workaround for broken support in Unity, Fluxbox and Xfwm
  - [X11] Bugfix: Mouse button `GLFW_MOUSE_BUTTON_4` was never used
  - [X11] Bugfix: `glfwTerminate` could close an unrelated file descriptor
  - [X11] Bugfix: Some WMs (KWM, Fluxbox) did not respect cursor redefinition

src/x11_window.c

@@ -439,27 +439,6 @@ static GLboolean createWindow(_GLFWwindow* window,
                         PropModeReplace, (unsigned char*) &version, 1);
     }
 
-    if (_glfw.x11.NET_REQUEST_FRAME_EXTENTS)
-    {
-        // Ensure _NET_FRAME_EXTENTS is set, allowing glfwGetWindowFrameSize to
-        // function before the window is mapped
-
-        XEvent event;
-        memset(&event, 0, sizeof(event));
-
-        event.type = ClientMessage;
-        event.xclient.window = window->x11.handle;
-        event.xclient.format = 32; // Data is 32-bit longs
-        event.xclient.message_type = _glfw.x11.NET_REQUEST_FRAME_EXTENTS;
-
-        XSendEvent(_glfw.x11.display,
-                   _glfw.x11.root,
-                   False,
-                   SubstructureNotifyMask | SubstructureRedirectMask,
-                   &event);
-        XIfEvent(_glfw.x11.display, &event, isFrameExtentsEvent, (XPointer) window);
-    }
-
     if (wndconfig->floating && !wndconfig->monitor)
     {
         if (_glfw.x11.NET_WM_STATE && _glfw.x11.NET_WM_STATE_ABOVE)
@@ -1607,6 +1586,55 @@ void _glfwPlatformGetWindowFrameSize(_GLFWwindow* window,
     if (_glfw.x11.NET_FRAME_EXTENTS == None)
         return;
 
+    if (!_glfwPlatformWindowVisible(window) &&
+        _glfw.x11.NET_REQUEST_FRAME_EXTENTS)
+    {
+        // Ensure _NET_FRAME_EXTENTS is set, allowing glfwGetWindowFrameSize to
+        // function before the window is mapped
+
+        double base;
+        XEvent event;
+        memset(&event, 0, sizeof(event));
+
+        event.type = ClientMessage;
+        event.xclient.window = window->x11.handle;
+        event.xclient.format = 32; // Data is 32-bit longs
+        event.xclient.message_type = _glfw.x11.NET_REQUEST_FRAME_EXTENTS;
+
+        XSendEvent(_glfw.x11.display,
+                   _glfw.x11.root,
+                   False,
+                   SubstructureNotifyMask | SubstructureRedirectMask,
+                   &event);
+
+        // HACK: Poll with timeout for the required response instead of blocking
+        //       This is done because some window managers (at least Unity,
+        //       Fluxbox and Xfwm) failed to send the required response
+        //       They have been fixed but broken versions are still in the wild
+        //       If you are affected by this and your window manager is NOT
+        //       listed above, PLEASE report it to their and our issue trackers
+        base = _glfwPlatformGetTime();
+        for (;;)
+        {
+            if (_glfwPlatformGetTime() - base > 0.5)
+            {
+                _glfwInputError(GLFW_PLATFORM_ERROR,
+                                "X11: The window manager has a broken "
+                                "_NET_REQUEST_FRAME_EXTENTS implementation; "
+                                "please report this issue");
+                break;
+            }
+
+            if (XCheckIfEvent(_glfw.x11.display,
+                              &event,
+                              isFrameExtentsEvent,
+                              (XPointer) window))
+            {
+                break;
+            }
+        }
+    }
+
     if (_glfwGetWindowProperty(window->x11.handle,
                                _glfw.x11.NET_FRAME_EXTENTS,
                                XA_CARDINAL,