vulkan: Dequeue the shared buffer again after presenting

Ensures that the shared buffer is always dequeued. This is tidier than
the previous hacky approach of dequeueing it on demand just prior to
this.

Test: build
Change-Id: I0202271a12106470329180b51a2eea19ceab31af

1 files changed, 25 insertions, 0 deletions

diff --git a/vulkan/libvulkan/swapchain.cpp b/vulkan/libvulkan/swapchain.cpp
index a4f968a7b2..2fee8a5fbf 100644
--- a/vulkan/libvulkan/swapchain.cpp
+++ b/vulkan/libvulkan/swapchain.cpp
@@ -1440,6 +1440,7 @@ VkResult QueuePresentKHR(VkQueue queue, const VkPresentInfoKHR* present_info) {
                             static_cast<int64_t>(time->desiredPresentTime));
                     }
                 }
+
                 err = window->queueBuffer(window, img.buffer.get(), fence);
                 // queueBuffer always closes fence, even on error
                 if (err != 0) {
@@ -1454,6 +1455,30 @@ VkResult QueuePresentKHR(VkQueue queue, const VkPresentInfoKHR* present_info) {
                     img.dequeue_fence = -1;
                 }
                 img.dequeued = false;
+
+                // If the swapchain is in shared mode, immediately dequeue the
+                // buffer so it can be presented again without an intervening
+                // call to AcquireNextImageKHR. We expect to get the same buffer
+                // back from every call to dequeueBuffer in this mode.
+                if (swapchain.shared && swapchain_result == VK_SUCCESS) {
+                    ANativeWindowBuffer* buffer;
+                    int fence_fd;
+                    err = window->dequeueBuffer(window, &buffer, &fence_fd);
+                    if (err != 0) {
+                        ALOGE("dequeueBuffer failed: %s (%d)", strerror(-err), err);
+                        swapchain_result = WorstPresentResult(swapchain_result,
+                            VK_ERROR_SURFACE_LOST_KHR);
+                    }
+                    else if (img.buffer != buffer) {
+                        ALOGE("got wrong image back for shared swapchain");
+                        swapchain_result = WorstPresentResult(swapchain_result,
+                            VK_ERROR_SURFACE_LOST_KHR);
+                    }
+                    else {
+                        img.dequeue_fence = fence_fd;
+                        img.dequeued = true;
+                    }
+                }
             }
             if (swapchain_result != VK_SUCCESS) {
                 ReleaseSwapchainImage(device, window, fence, img);