Cocoa: Fix window rect on leaving video mode

Fixes #748.

README.md

@@ -183,6 +183,8 @@ information on what to include when reporting a bug.
                   function on macOS 10.12+
 - [Cocoa] Bugfix: Running in AppSandbox would emit warnings (#816,#882)
 - [Cocoa] Bugfix: Windows created after the first were not cascaded (#195)
+- [Cocoa] Bugfix: Leaving video mode with `glfwSetWindowMonitor` would set
+                  incorrect position and size (#748)
 - [X11] Moved to XI2 `XI_RawMotion` for disable cursor mode motion input (#125)
 - [EGL] Added support for `EGL_KHR_get_all_proc_addresses` (#871)
 - [EGL] Bugfix: The test for `EGL_RGB_BUFFER` was invalid

src/cocoa_window.m

@@ -1310,6 +1310,10 @@ void _glfwPlatformSetWindowMonitor(_GLFWwindow* window,
 
     _glfwInputWindowMonitorChange(window, monitor);
 
+    // HACK: Allow the state cached in Cocoa to catch up to reality
+    // TODO: Solve this in a less terrible way
+    _glfwPlatformPollEvents();
+
     const NSUInteger styleMask = getStyleMask(window);
     [window->ns.object setStyleMask:styleMask];
     [window->ns.object makeFirstResponder:window->ns.view];