From dc4de5b7c7b3f9aba4b3b4d1acda8d45736148ca Mon Sep 17 00:00:00 2001
From: Brandon Wright <bearoso@gmail.com>
Date: Mon, 3 Dec 2018 17:28:22 -0600
Subject: [PATCH] GTK+: OpenGL: Add fences as glFinish alternative.

---
 gtk/src/gtk_display_driver_opengl.cpp | 17 +++++++++++++++--
 gtk/src/gtk_display_driver_opengl.h   |  1 +
 gtk/src/gtk_glx_context.cpp           |  2 ++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/gtk/src/gtk_display_driver_opengl.cpp b/gtk/src/gtk_display_driver_opengl.cpp
index 8d1f4d53..eeb20a22 100644
--- a/gtk/src/gtk_display_driver_opengl.cpp
+++ b/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);
-        glFinish ();
+        if (fences)
+        {
+            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 ();
+        }
     }
 }
 
diff --git a/gtk/src/gtk_display_driver_opengl.h b/gtk/src/gtk_display_driver_opengl.h
index 8c91deaf..d6696efb 100644
--- a/gtk/src/gtk_display_driver_opengl.h
+++ b/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;
diff --git a/gtk/src/gtk_glx_context.cpp b/gtk/src/gtk_glx_context.cpp
index 4b684629..804a29a9 100644
--- a/gtk/src/gtk_glx_context.cpp
+++ b/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);
 }