From 85c83d2417703ed056d29bf474e82b333bdbf6d4 Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Wed, 13 Dec 2017 05:55:01 +1100
Subject: [PATCH] [client] enable vsync again but draw to front for cursor
 updates

---
 client/main.c             |  1 -
 client/renderers/opengl.c | 20 +++++++++++++++-----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/client/main.c b/client/main.c
index a79beef6..ba2c8a2d 100644
--- a/client/main.c
+++ b/client/main.c
@@ -661,7 +661,6 @@ int run()
     FcPatternDestroy(pat);
   }
 
-  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 0);
   state.window = SDL_CreateWindow(
     "Looking Glass (Client)",
     params.center ? SDL_WINDOWPOS_CENTERED : params.x,
diff --git a/client/renderers/opengl.c b/client/renderers/opengl.c
index a5e7e5e5..285ca5b7 100644
--- a/client/renderers/opengl.c
+++ b/client/renderers/opengl.c
@@ -124,7 +124,7 @@ bool lgr_opengl_initialize(void ** opaque, const LG_RendererParams params, const
     }
   }
 
-  SDL_GL_SetSwapInterval(0);
+  SDL_GL_SetSwapInterval(1);
 
   // check if the GPU supports GL_ARB_buffer_storage first
   // there is no advantage to this renderer if it is not present.
@@ -669,16 +669,24 @@ bool lgr_opengl_render(void * opaque)
       glEnable(GL_SCISSOR_TEST);
     }
 
-    glXWaitVideoSyncSGI(1, 0, &this->gpuFrameCount);
-    glFinish();
-
     glCallList(this->texList + this->texIndex);
     this->mouseRepair = false;
     lgr_opengl_draw_mouse(this);
     if (this->fpsTexture)
       glCallList(this->fpsList);
 
-    glFlush();
+    glXGetVideoSyncSGI(&this->gpuFrameCount);
+    SDL_GL_SwapWindow(this->params.window);
+
+    unsigned int count;
+    glXGetVideoSyncSGI(&count);
+    while(count == this->gpuFrameCount)
+    {
+      unsigned int remainder;
+      glXWaitVideoSyncSGI(1, 0, &remainder);
+      glXGetVideoSyncSGI(&count);
+      glFinish();
+    }
 
     ++this->frameCount;
     const uint64_t t    = nanotime();
@@ -688,8 +696,10 @@ bool lgr_opengl_render(void * opaque)
   else
     if (this->mouseUpdate)
     {
+      glDrawBuffer(GL_FRONT);
       lgr_opengl_draw_mouse(this);
       glFlush();
+      glDrawBuffer(GL_BACK);
     }