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.

2 files changed, 34 insertions, 3 deletions

diff --git a/demos/cube.c b/demos/cube.c
index 8c50858c..e3f3c45d 100644
--- a/demos/cube.c
+++ b/demos/cube.c
@@ -205,6 +205,7 @@ struct demo {
         XGL_GPU_MEMORY mem;
 
         XGL_COLOR_ATTACHMENT_VIEW view;
+        XGL_FENCE fence;
     } buffers[DEMO_BUFFER_COUNT];
 
     struct {
@@ -348,17 +349,22 @@ static void demo_draw(struct demo *demo)
     const XGL_WSI_X11_PRESENT_INFO present = {
         .destWindow = demo->window,
         .srcImage = demo->buffers[demo->current_buffer].image,
-        .async = false
+        .async = true,
+        .flip = false,
     };
+    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;
@@ -375,6 +381,11 @@ static void demo_prepare_buffers(struct demo *demo)
         },
         .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;
 
@@ -397,6 +408,10 @@ static void demo_prepare_buffers(struct demo *demo)
         err = xglCreateColorAttachmentView(demo->device,
                 &color_attachment_view, &demo->buffers[i].view);
         assert(!err);
+
+        err = xglCreateFence(demo->device,
+                &fence, &demo->buffers[i].fence);
+        assert(!err);
     }
 }
 
@@ -1324,6 +1339,7 @@ static void demo_cleanup(struct demo *demo)
     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);
     }
diff --git a/demos/tri.c b/demos/tri.c
index 9aae4292..3d9be2d9 100644
--- a/demos/tri.c
+++ b/demos/tri.c
@@ -36,6 +36,7 @@ struct demo {
         XGL_GPU_MEMORY mem;
 
         XGL_COLOR_ATTACHMENT_VIEW view;
+        XGL_FENCE fence;
     } buffers[DEMO_BUFFER_COUNT];
 
     struct {
@@ -142,15 +143,19 @@ static void demo_draw(struct demo *demo)
         .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 @@ static void demo_prepare_buffers(struct demo *demo)
         },
         .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 @@ static void demo_prepare_buffers(struct demo *demo)
         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 @@ static void demo_cleanup(struct demo *demo)
     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);
     }