Allow setting swap interval to zero on DWM.

README.md

@@ -39,6 +39,7 @@ guide in the GLFW documentation.
  - Renamed configuration header to `glfw_config.h` to avoid conflicts
  - Bugfix: The `glfw3.pc` file did not respect the `LIB_SUFFIX` CMake option
  - Bugfix: The `joysticks` test would segfault if a controller had no axes
+ - [Win32] Allowed swap interval to be explicitly set to zero on DWM systems
  - [Win32] Bugfix: Removed joystick axis value negation left over from GLFW 2
  - [Win32] Bugfix: Restoring windows using the Win+D hot key did not trigger the
                    focus callback

src/wgl_context.c

@@ -606,7 +606,7 @@ void _glfwPlatformSwapInterval(int interval)
     _GLFWwindow* window = _glfwPlatformGetCurrentContext();
 
 #if !defined(_GLFW_USE_DWM_SWAP_INTERVAL)
-    if (_glfwIsCompositionEnabled())
+    if (_glfwIsCompositionEnabled() && interval)
     {
         // Don't enabled vsync when desktop compositing is enabled, as it leads
         // to frame jitter