GTK+: OpenGL: Add fences as glFinish alternative.

gtk/src/gtk_display_driver_opengl.cpp

@@ -584,6 +584,9 @@ int S9xOpenGLDisplayDriver::create_context ()
     else
         core = false;
 
+    if (version >= 31 || epoxy_has_gl_extension ("GL_ARB_sync"))
+        fences = true;
+
     return 1;
 }
 
@@ -640,8 +643,18 @@ void S9xOpenGLDisplayDriver::swap_buffers ()
 
     if (config->sync_every_frame)
     {
-        usleep (0);
+        if (fences)
-        glFinish ();
+        {
+            GLsync fence = glFenceSync (GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
+            usleep (0);
+            glClientWaitSync (fence, GL_SYNC_FLUSH_COMMANDS_BIT, 100000000);
+            glDeleteSync (fence);
+        }
+        else
+        {
+            usleep (0);
+            glFinish ();
+        }
     }
 }
 

gtk/src/gtk_display_driver_opengl.h

@@ -63,6 +63,7 @@ class S9xOpenGLDisplayDriver : public S9xDisplayDriver
         bool              npot;
         bool              using_pbos;
         bool              initialized;
+        bool              fences;
 
         bool              using_glsl_shaders;
         GLSLShader        *glsl_shader;

gtk/src/gtk_glx_context.cpp

@@ -156,6 +156,8 @@ void GTKGLXContext::swap_interval (int frames)
         glXSwapIntervalEXT (display, xid, frames);
     else if (epoxy_has_glx_extension (display, screen, "GLX_SGI_swap_control"))
         glXSwapIntervalSGI (frames);
+    else if (epoxy_has_glx_extension (display, screen, "GLX_MESA_swap_control"))
+        glXSwapIntervalMESA (frames);
 }