From a512576efc870650b2d3fa018891b2a1cdf4b613 Mon Sep 17 00:00:00 2001
From: Jordan Halase <jordan@halase.me>
Date: Mon, 11 Nov 2019 12:46:36 -0600
Subject: Automatically collect swapchain garbage

---
 main.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/main.c b/main.c
index 3903579..2e38bf2 100755
--- a/main.c
+++ b/main.c
@@ -1600,24 +1600,32 @@ static bool canDestroySwapchain(const struct RenderVulkan *vk,
 	return !notReady;
 }
 
-/* FIXME: Race condition! Swapchains cannot be destroyed until they are done
- *        being rendered to.
+/** Collects old swapchains only, leaving the latest one intact. This will
+ * only delete the swapchains not in use.
  */
 void rvkCollectSwapchainGarbage(struct RenderVulkan *vk)
 {
-	struct SwapchainVulkan *old, *pp = vk->swapchain;
-	uint32_t count = 0;
-	if (pp && (pp)->old) {
-		for(pp = (pp)->old; pp; pp = old) {
-			old = (pp)->old;
-			rvkDestroySwapchain(vk, pp);
+	struct SwapchainVulkan *old, *sc, *lag = vk->swapchain;
+	uint32_t count = 0, del = 0;
+	if (lag && lag->old) {
+		for(sc = lag->old; sc; sc = old) {
+			old = sc->old;
+			if (canDestroySwapchain(vk, sc)) {
+				rvkDestroySwapchain(vk, sc);
+				lag->old = old;
+				++del;
+			} else {
+				lag = lag->old;
+			}
 			++count;
 		}
-		vk->swapchain->old = NULL;
 	}
-	printf("Collected %d retired swapchains\n", count);
+	if (count > 1) {
+		printf("Collected %d/%d retired swapchains\n", del, count);
+	}
 }
 
+/** This must not be called until all swapchains are no longer in use. */
 void rvkDestroyAllSwapchains(struct RenderVulkan *vk)
 {
 	struct SwapchainVulkan *swapchain, *old;
@@ -1821,6 +1829,7 @@ PuglStatus onDisplay(PuglView *view)
 
 	vk->dev->vkQueuePresentKHR(vk->graphicsQueue, &presentInfo);
 
+	rvkCollectSwapchainGarbage(vk);
 	if (args.continuous) ++framesDrawn;
 	return PUGL_SUCCESS;
 }
@@ -1864,7 +1873,6 @@ PuglStatus onEvent(PuglView *view, const PuglEvent *e)
 			break;
 		case 'c':
 			// Manually collect swapchain garbage
-			vk->dev->vkDeviceWaitIdle(vk->device);
 			rvkCollectSwapchainGarbage(vk);
 			break;
 		}
-- 
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