+ /* When presenting on a different queue than where we're drawing the
+ * overlay *AND* when the application does not provide a semaphore to
+ * vkQueuePresent, insert our own cross engine synchronization
+ * semaphore.
+ */
+ if (n_wait_semaphores == 0 && device_data->graphic_queue->queue != present_queue->queue) {
+ VkPipelineStageFlags stages_wait = VK_PIPELINE_STAGE_ALL_COMMANDS_BIT;
+ VkSubmitInfo submit_info = {};
+ submit_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
+ submit_info.commandBufferCount = 0;
+ submit_info.pWaitDstStageMask = &stages_wait;
+ submit_info.waitSemaphoreCount = 0;
+ submit_info.signalSemaphoreCount = 1;
+ submit_info.pSignalSemaphores = &draw->cross_engine_semaphore;
+
+ device_data->vtable.QueueSubmit(present_queue->queue, 1, &submit_info, VK_NULL_HANDLE);
+
+ submit_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
+ submit_info.commandBufferCount = 1;
+ submit_info.pWaitDstStageMask = &stages_wait;
+ submit_info.pCommandBuffers = &draw->command_buffer;
+ submit_info.waitSemaphoreCount = 1;
+ submit_info.pWaitSemaphores = &draw->cross_engine_semaphore;
+ submit_info.signalSemaphoreCount = 1;
+ submit_info.pSignalSemaphores = &draw->semaphore;
+
+ device_data->vtable.QueueSubmit(device_data->graphic_queue->queue, 1, &submit_info, draw->fence);
+ } else {
+ VkPipelineStageFlags *stages_wait = (VkPipelineStageFlags*) malloc(sizeof(VkPipelineStageFlags) * n_wait_semaphores);
+ for (unsigned i = 0; i < n_wait_semaphores; i++)
+ {
+ // wait in the fragment stage until the swapchain image is ready
+ stages_wait[i] = VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT;
+ }
+
+ VkSubmitInfo submit_info = {};
+ submit_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
+ submit_info.commandBufferCount = 1;
+ submit_info.pCommandBuffers = &draw->command_buffer;
+ submit_info.pWaitDstStageMask = stages_wait;
+ submit_info.waitSemaphoreCount = n_wait_semaphores;
+ submit_info.pWaitSemaphores = wait_semaphores;
+ submit_info.signalSemaphoreCount = 1;
+ submit_info.pSignalSemaphores = &draw->semaphore;
+
+ device_data->vtable.QueueSubmit(device_data->graphic_queue->queue, 1, &submit_info, draw->fence);
+
+ free(stages_wait);