Added support for vertical syncing via the Windows OS compositor (DWM.)

4 files changed, 47 insertions, 3 deletions

diff --git a/platform/windows/context_gl_windows.cpp b/platform/windows/context_gl_windows.cpp
index e715999378..34a5698394 100644
--- a/platform/windows/context_gl_windows.cpp
+++ b/platform/windows/context_gl_windows.cpp
@@ -34,6 +34,8 @@
 
 #include "context_gl_windows.h"
 
+#include <dwmapi.h>
+
 #define WGL_CONTEXT_MAJOR_VERSION_ARB 0x2091
 #define WGL_CONTEXT_MINOR_VERSION_ARB 0x2092
 #define WGL_CONTEXT_FLAGS_ARB 0x2094
@@ -63,16 +65,52 @@ int ContextGL_Windows::get_window_height() {
 	return OS::get_singleton()->get_video_mode().height;
 }
 
+bool ContextGL_Windows::should_vsync_via_compositor() {
+
+	if (OS::get_singleton()->is_window_fullscreen() || !OS::get_singleton()->is_vsync_via_compositor_enabled()) {
+		return false;
+	}
+
+	// Note: All Windows versions supported by Godot have a compositor.
+	// It can be disabled on earlier Windows versions.
+	BOOL dwm_enabled;
+
+	if (SUCCEEDED(DwmIsCompositionEnabled(&dwm_enabled))) {
+		return dwm_enabled;
+	}
+
+	return false;
+}
+
 void ContextGL_Windows::swap_buffers() {
 
 	SwapBuffers(hDC);
+
+	if (use_vsync) {
+		bool vsync_via_compositor_now = should_vsync_via_compositor();
+
+		if (vsync_via_compositor_now) {
+			DwmFlush();
+		}
+
+		if (vsync_via_compositor_now != vsync_via_compositor) {
+			// The previous frame had a different operating mode than this
+			// frame.  Set the 'vsync_via_compositor' member variable and the
+			// OpenGL swap interval to their proper values.
+			set_use_vsync(true);
+		}
+	}
 }
 
 void ContextGL_Windows::set_use_vsync(bool p_use) {
 
+	vsync_via_compositor = p_use && should_vsync_via_compositor();
+
 	if (wglSwapIntervalEXT) {
-		wglSwapIntervalEXT(p_use ? 1 : 0);
+		int swap_interval = (p_use && !vsync_via_compositor) ? 1 : 0;
+		wglSwapIntervalEXT(swap_interval);
 	}
+
 	use_vsync = p_use;
 }
 
@@ -177,6 +215,7 @@ ContextGL_Windows::ContextGL_Windows(HWND hwnd, bool p_opengl_3_context) {
 	opengl_3_context = p_opengl_3_context;
 	hWnd = hwnd;
 	use_vsync = false;
+	vsync_via_compositor = false;
 }
 
 ContextGL_Windows::~ContextGL_Windows() {
diff --git a/platform/windows/context_gl_windows.h b/platform/windows/context_gl_windows.h
index d23fba50e1..e65ea1928f 100644
--- a/platform/windows/context_gl_windows.h
+++ b/platform/windows/context_gl_windows.h
@@ -50,9 +50,12 @@ class ContextGL_Windows {
 	HWND hWnd;
 	bool opengl_3_context;
 	bool use_vsync;
+	bool vsync_via_compositor;
 
 	PFNWGLSWAPINTERVALEXTPROC wglSwapIntervalEXT;
 
+	static bool should_vsync_via_compositor();
+
 public:
 	void release_current();
 
diff --git a/platform/windows/detect.py b/platform/windows/detect.py
index 9a2b2bcb98..b37a21f37f 100644
--- a/platform/windows/detect.py
+++ b/platform/windows/detect.py
@@ -221,7 +221,8 @@ def configure_msvc(env, manual_msvc_config):
 
     LIBS = ['winmm', 'opengl32', 'dsound', 'kernel32', 'ole32', 'oleaut32',
             'user32', 'gdi32', 'IPHLPAPI', 'Shlwapi', 'wsock32', 'Ws2_32',
-	    'shell32', 'advapi32', 'dinput8', 'dxguid', 'imm32', 'bcrypt','Avrt']
+            'shell32', 'advapi32', 'dinput8', 'dxguid', 'imm32', 'bcrypt','Avrt',
+            'dwmapi']
     env.Append(LINKFLAGS=[p + env["LIBSUFFIX"] for p in LIBS])
 
     if manual_msvc_config:
@@ -348,7 +349,7 @@ def configure_mingw(env):
     env.Append(CCFLAGS=['-mwindows'])
     env.Append(CPPDEFINES=['WINDOWS_ENABLED', 'OPENGL_ENABLED', 'WASAPI_ENABLED', 'WINMIDI_ENABLED'])
     env.Append(CPPDEFINES=[('WINVER', env['target_win_version']), ('_WIN32_WINNT', env['target_win_version'])])
-    env.Append(LIBS=['mingw32', 'opengl32', 'dsound', 'ole32', 'd3d9', 'winmm', 'gdi32', 'iphlpapi', 'shlwapi', 'wsock32', 'ws2_32', 'kernel32', 'oleaut32', 'dinput8', 'dxguid', 'ksuser', 'imm32', 'bcrypt', 'avrt', 'uuid'])
+    env.Append(LIBS=['mingw32', 'opengl32', 'dsound', 'ole32', 'd3d9', 'winmm', 'gdi32', 'iphlpapi', 'shlwapi', 'wsock32', 'ws2_32', 'kernel32', 'oleaut32', 'dinput8', 'dxguid', 'ksuser', 'imm32', 'bcrypt', 'avrt', 'uuid', 'dwmapi'])
 
     env.Append(CPPDEFINES=['MINGW_ENABLED', ('MINGW_HAS_SECURE_API', 1)])
 
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index 9c1514f541..f749134f3c 100755
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -1480,6 +1480,7 @@ Error OS_Windows::initialize(const VideoMode &p_desired, int p_video_driver, int
 	video_driver_index = p_video_driver;
 
 	gl_context->set_use_vsync(video_mode.use_vsync);
+	set_vsync_via_compositor(video_mode.vsync_via_compositor);
 #endif
 
 	visual_server = memnew(VisualServerRaster);