Fixed enumeration of invalid video modes.

Fixes #350.

README.md

@@ -67,6 +67,7 @@ GLFW bundles a number of dependencies in the `deps/` directory.
  - Bugfix: The cached current context could get out of sync
  - [Win32] Renamed hybrid GPU override compile-time option to
            `_GLFW_USE_HYBRID_HPG` and added support for AMD PowerXpress systems
+ - [Win32] Bugfix: `glfwGetVideoModes` included unusable modes on some systems
  - [Cocoa] Bugfix: The cached `NSScreen` for a monitor could get out of sync
  - [Cocoa] Bugfix: The `GLFW_AUTO_ICONIFY` window hint was ignored
  - [Cocoa] Bugfix: Resizing a window to its minimum size would segfault

src/win32_monitor.c

@@ -226,6 +226,15 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
 
         modeIndex++;
 
+        if (ChangeDisplaySettingsExW(monitor->win32.adapterName,
+                                    &dm,
+                                    NULL,
+                                    CDS_TEST,
+                                    NULL) != DISP_CHANGE_SUCCESSFUL)
+        {
+            continue;
+        }
+
         // Skip modes with less than 15 BPP
         if (dm.dmBitsPerPel < 15)
             continue;