Win32: Clean up DWM detection

src/wgl_context.c

@@ -256,12 +256,20 @@ static void makeContextCurrentWGL(_GLFWwindow* window)
 
 static void swapBuffersWGL(_GLFWwindow* window)
 {
-    // HACK: Use DwmFlush when desktop composition is enabled
-    if (_glfwIsCompositionEnabledWin32() && !window->monitor)
+    if (!window->monitor)
     {
-        int count = abs(window->context.wgl.interval);
-        while (count--)
-            DwmFlush();
+        if (IsWindowsVistaOrGreater())
+        {
+            BOOL enabled;
+
+            // HACK: Use DwmFlush when desktop composition is enabled
+            if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled)
+            {
+                int count = abs(window->context.wgl.interval);
+                while (count--)
+                    DwmFlush();
+            }
+        }
     }
 
     SwapBuffers(window->context.wgl.dc);
@@ -273,10 +281,18 @@ static void swapIntervalWGL(int interval)
 
     window->context.wgl.interval = interval;
 
-    // HACK: Disable WGL swap interval when desktop composition is enabled to
-    //       avoid interfering with DWM vsync
-    if (_glfwIsCompositionEnabledWin32() && !window->monitor)
-        interval = 0;
+    if (!window->monitor)
+    {
+        if (IsWindowsVistaOrGreater())
+        {
+            BOOL enabled;
+
+            // HACK: Disable WGL swap interval when desktop composition is enabled to
+            //       avoid interfering with DWM vsync
+            if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled)
+                interval = 0;
+        }
+    }
 
     if (_glfw.wgl.EXT_swap_control)
         _glfw.wgl.SwapIntervalEXT(interval);

src/win32_platform.h

@@ -396,7 +396,6 @@ typedef struct _GLFWmutexWin32
 
 GLFWbool _glfwRegisterWindowClassWin32(void);
 void _glfwUnregisterWindowClassWin32(void);
-GLFWbool _glfwIsCompositionEnabledWin32(void);
 
 WCHAR* _glfwCreateWideStringFromUTF8Win32(const char* source);
 char* _glfwCreateUTF8FromWideStringWin32(const WCHAR* source);

src/win32_window.c

@@ -351,10 +351,12 @@ static void updateWindowStyles(const _GLFWwindow* window)
 //
 static void updateFramebufferTransparency(const _GLFWwindow* window)
 {
+    BOOL enabled;
+
     if (!IsWindowsVistaOrGreater())
         return;
 
-    if (_glfwIsCompositionEnabledWin32())
+    if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled)
     {
         HRGN region = CreateRectRgn(0, 0, -1, -1);
         DWM_BLURBEHIND bb = {0};
@@ -1221,20 +1223,6 @@ void _glfwUnregisterWindowClassWin32(void)
     UnregisterClassW(_GLFW_WNDCLASSNAME, GetModuleHandleW(NULL));
 }
 
-// Returns whether desktop compositing is enabled
-//
-GLFWbool _glfwIsCompositionEnabledWin32(void)
-{
-    if (IsWindowsVistaOrGreater())
-    {
-        BOOL enabled;
-        if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)))
-            return enabled;
-    }
-
-    return FALSE;
-}
-
 
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW platform API                      //////
@@ -1632,7 +1620,15 @@ int _glfwPlatformWindowHovered(_GLFWwindow* window)
 
 int _glfwPlatformFramebufferTransparent(_GLFWwindow* window)
 {
-    return window->win32.transparent && _glfwIsCompositionEnabledWin32();
+    BOOL enabled;
+
+    if (!window->win32.transparent)
+        return GLFW_FALSE;
+
+    if (!IsWindowsVistaOrGreater())
+        return GLFW_FALSE;
+
+    return SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled;
 }
 
 void _glfwPlatformSetWindowResizable(_GLFWwindow* window, GLFWbool enabled)