commit 68040a41017a2e9e81a86af2d083a3079e882b96
author Chia-I Wu <olv@lunarg.com> Fri Nov 07 14:30:34 2014 +0800
committer Courtney Goeltzenleuchter <courtney@LunarG.com> Fri Nov 21 16:49:39 2014 -0700
tree 38054f0bb836199a8a205b74a06853216ca3bda7
parent 7fbe2abcfa288461632eb520e3a2c50d68540d8c

demos: add a fence for presentation

After xglWsiX11QueuePresent(), the image is scheduled for copying.  We should
not render to it until the copying is done.  Otherwise, depending on how the
DDX works, flickering or GPU hangs may be expected.

Add and wait on the fence before submitting the command buffer.  This ensures
the DDX is done with the image.   Set async to true to run as fast as
possible.

demos/tri.c

diff --git a/demos/tri.c b/demos/tri.c
index 9aae429..3d9be2d 100644
--- a/demos/tri.c
+++ b/demos/tri.c
@@ -36,6 +36,7 @@
         XGL_GPU_MEMORY mem;
 
         XGL_COLOR_ATTACHMENT_VIEW view;
+        XGL_FENCE fence;
     } buffers[DEMO_BUFFER_COUNT];
 
     struct {
@@ -142,15 +143,19 @@
         .destWindow = demo->window,
         .srcImage = demo->buffers[demo->current_buffer].image,
     };
+    XGL_FENCE fence = demo->buffers[demo->current_buffer].fence;
     XGL_RESULT err;
 
     demo_draw_build_cmd(demo);
 
+    err = xglWaitForFences(demo->device, 1, &fence, XGL_TRUE, ~((XGL_UINT64) 0));
+    assert(err == XGL_SUCCESS || err == XGL_ERROR_UNAVAILABLE);
+
     err = xglQueueSubmit(demo->queue, 1, &demo->cmd,
             0, NULL, XGL_NULL_HANDLE);
     assert(!err);
 
-    err = xglWsiX11QueuePresent(demo->queue, &present, XGL_NULL_HANDLE);
+    err = xglWsiX11QueuePresent(demo->queue, &present, fence);
     assert(!err);
 
     demo->current_buffer = (demo->current_buffer + 1) % DEMO_BUFFER_COUNT;
@@ -167,6 +172,11 @@
         },
         .flags = 0,
     };
+    const XGL_FENCE_CREATE_INFO fence = {
+        .sType = XGL_STRUCTURE_TYPE_FENCE_CREATE_INFO,
+        .pNext = NULL,
+        .flags = 0,
+    };
     XGL_RESULT err;
     XGL_UINT i;
 
@@ -189,6 +199,10 @@
         err = xglCreateColorAttachmentView(demo->device,
                 &color_attachment_view, &demo->buffers[i].view);
         assert(!err);
+
+        err = xglCreateFence(demo->device,
+                &fence, &demo->buffers[i].fence);
+        assert(!err);
     }
 }
 
@@ -894,6 +908,7 @@
     xglFreeMemory(demo->depth.mem);
 
     for (i = 0; i < DEMO_BUFFER_COUNT; i++) {
+        xglDestroyObject(demo->buffers[i].fence);
         xglDestroyObject(demo->buffers[i].view);
         xglDestroyObject(demo->buffers[i].image);
     }