ruby: use wglSwapInterval rather than DwmFlush

Despite GFWL, and other sources recommending the DwmFlush approach, actual users are setting better results the old way.

ruby/video/wgl.cpp

@@ -1,5 +1,4 @@
 #include "opengl/opengl.hpp"
-#include <dwmapi.h>
 
 #define WGL_CONTEXT_MAJOR_VERSION_ARB 0x2091
 #define WGL_CONTEXT_MINOR_VERSION_ARB 0x2092
@@ -41,6 +40,9 @@ struct VideoWGL : VideoDriver, OpenGL {
   }
 
   auto setBlocking(bool blocking) -> bool override {
+    acquireContext();
+    if(wglSwapInterval) wglSwapInterval(blocking);
+    releaseContext();
     return true;
   }
 
@@ -105,7 +107,6 @@ struct VideoWGL : VideoDriver, OpenGL {
     OpenGL::output();
 
     SwapBuffers(_display);
-    if(self.blocking) DwmFlush(); // DwmFlush waits for VSYNC at compositor level, bypassing OpenGL driver bugs
     if(self.flush) glFinish();
     releaseContext();
   }
@@ -188,7 +189,7 @@ struct VideoWGL : VideoDriver, OpenGL {
       }
     }
 
-    if(wglSwapInterval) wglSwapInterval(0);
+    if(wglSwapInterval) wglSwapInterval(self.blocking);
     _ready = OpenGL::initialize(self.shader);
     releaseContext();
     return _ready;