From fb8921f69c20f04bd2ca9412eddfc1f2b3143897 Mon Sep 17 00:00:00 2001
From: Kenny Levinsen <kl@kl.wtf>
Date: Sun, 7 Jul 2024 16:07:18 +0200
Subject: [PATCH] render/vulkan: Cache blending buffer on swapchain

Our blending buffer is 64 bits per pixel, and triple the amount of
memory needed for each swapchain buffer. To save some memory, keep a
single blending buffer per swapchain.
---
 render/vulkan/renderer.c | 62 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 60 insertions(+), 2 deletions(-)

diff --git a/render/vulkan/renderer.c b/render/vulkan/renderer.c
index 7adcc46da..b0668283e 100644
--- a/render/vulkan/renderer.c
+++ b/render/vulkan/renderer.c
@@ -10,6 +10,7 @@
 #include <vulkan/vulkan.h>
 #include <wlr/render/color.h>
 #include <wlr/render/interface.h>
+#include <wlr/render/swapchain.h>
 #include <wlr/types/wlr_drm.h>
 #include <wlr/util/box.h>
 #include <wlr/util/log.h>
@@ -638,6 +639,23 @@ static struct wlr_addon_interface render_buffer_addon_impl = {
 	.destroy = handle_render_buffer_destroy,
 };
 
+struct vulkan_swapchain_blend_buffer {
+	struct wlr_addon swapchain_addon;
+	struct wlr_vk_blend_buffer *blend_buffer;
+};
+
+static void handle_swapchain_destroy(struct wlr_addon *addon) {
+	struct vulkan_swapchain_blend_buffer *bb =
+		wl_container_of(addon, bb, swapchain_addon);
+	vulkan_blend_buffer_unref(bb->blend_buffer);
+	wlr_addon_finish(&bb->swapchain_addon);
+}
+
+static struct wlr_addon_interface vulkan_swapchain_blend_buffer_addon_impl = {
+	.name = "vulkan_swapchain_blend_buffer",
+	.destroy = handle_swapchain_destroy,
+};
+
 static struct wlr_vk_blend_buffer *vulkan_create_blend_buffer(
 		struct wlr_vk_renderer *renderer, int width, int height) {
 	VkResult res;
@@ -740,14 +758,54 @@ error:
 	return NULL;
 }
 
+static struct wlr_vk_blend_buffer *vulkan_get_swapchain_blend_buffer(
+		struct wlr_vk_renderer *renderer, struct wlr_swapchain *swapchain,
+		int width, int height) {
+
+	if (!swapchain) {
+		wlr_log(WLR_DEBUG, "No swapchain for blending buffer");
+		return vulkan_create_blend_buffer(renderer, width, height);
+	}
+
+	struct vulkan_swapchain_blend_buffer *sbb;
+	struct wlr_addon *addon = wlr_addon_find(&swapchain->addons, renderer,
+			&vulkan_swapchain_blend_buffer_addon_impl);
+	if (addon) {
+		wlr_log(WLR_DEBUG, "Reusing blending buffer");
+		sbb = wl_container_of(addon, sbb, swapchain_addon);
+		return sbb->blend_buffer;
+	}
+
+	sbb = calloc(1, sizeof(*sbb));
+	if (!sbb) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		return NULL;
+	}
+
+	struct wlr_vk_blend_buffer *bb = vulkan_create_blend_buffer(renderer, width, height);
+	if (!bb) {
+		free(sbb);
+		return NULL;
+	}
+	sbb->blend_buffer = vulkan_blend_buffer_ref(bb);
+
+	wlr_log(WLR_DEBUG, "New swapchain blending buffer");
+
+	wlr_addon_init(&sbb->swapchain_addon, &swapchain->addons, renderer,
+			&vulkan_swapchain_blend_buffer_addon_impl);
+	return sbb->blend_buffer;
+}
+
 bool vulkan_setup_plain_framebuffer(struct wlr_vk_render_buffer *buffer,
 		const struct wlr_dmabuf_attributes *dmabuf) {
 	struct wlr_vk_renderer *renderer = buffer->renderer;
 	VkResult res;
 	VkDevice dev = renderer->dev->dev;
 
-	struct wlr_vk_blend_buffer *bb = vulkan_create_blend_buffer(renderer,
-			dmabuf->width, dmabuf->height);
+	struct wlr_swapchain *swapchain =
+		wlr_swapchain_try_from_wlr_buffer(buffer->wlr_buffer);
+	struct wlr_vk_blend_buffer *bb = vulkan_get_swapchain_blend_buffer(renderer,
+			swapchain, dmabuf->width, dmabuf->height);
 	if (!bb) {
 		return false;
 	}