From efe8e41b6162559ea8c6df529f93f166b76c1f0c Mon Sep 17 00:00:00 2001
From: Matthew Waters <matthew@centricular.com>
Date: Mon, 23 May 2022 11:26:24 +1000
Subject: [PATCH] vkfullscreenquad: add support for disabling clearing

e.g. if drawing over the top of an existing image, we don'w want to
clear.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2470>
---
 .../gst-libs/gst/vulkan/gstvkfullscreenquad.c | 30 ++++++++++++++++++-
 .../gst-libs/gst/vulkan/gstvkfullscreenquad.h |  3 ++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.c b/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.c
index 40dcd85b4e..816b8d64d9 100644
--- a/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.c
+++ b/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.c
@@ -65,6 +65,8 @@ struct _GstVulkanFullScreenQuadPrivate
   VkBlendFactor dst_alpha_blend_factor;
   VkBlendOp colour_blend_op;
   VkBlendOp alpha_blend_op;
+
+  gboolean enable_clear;
 };
 
 G_DEFINE_TYPE_WITH_CODE (GstVulkanFullScreenQuad, gst_vulkan_full_screen_quad,
@@ -300,7 +302,7 @@ create_render_pass (GstVulkanFullScreenQuad * self, GError ** error)
     color_attachments[i] = (VkAttachmentDescription) {
         .format = gst_vulkan_format_from_video_info (&self->out_info, i),
         .samples = VK_SAMPLE_COUNT_1_BIT,
-        .loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR,
+        .loadOp = priv->enable_clear ? VK_ATTACHMENT_LOAD_OP_CLEAR : VK_ATTACHMENT_LOAD_OP_LOAD,
         .storeOp = VK_ATTACHMENT_STORE_OP_STORE,
         .stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE,
         .stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE,
@@ -1326,6 +1328,32 @@ gst_vulkan_full_screen_quad_set_blend_operation (GstVulkanFullScreenQuad * self,
   clear_graphics_pipeline (self);
 }
 
+/**
+ * gst_vulkan_full_screen_quad_enable_clear:
+ * @self: the #GstVulkanFullScreenQuad
+ * @enable_clear: whether to clear the framebuffer on load
+ *
+ * Since: 1.22
+ */
+void
+gst_vulkan_full_screen_quad_enable_clear (GstVulkanFullScreenQuad * self,
+    gboolean enable_clear)
+{
+  GstVulkanFullScreenQuadPrivate *priv;
+
+  g_return_if_fail (GST_IS_VULKAN_FULL_SCREEN_QUAD (self));
+
+  priv = GET_PRIV (self);
+
+  if (priv->enable_clear == enable_clear)
+    return;
+
+  priv->enable_clear = enable_clear;
+
+  clear_graphics_pipeline (self);
+  clear_render_pass (self);
+}
+
 /**
  * gst_vulkan_full_screen_quad_prepare_draw:
  * @self: the #GstVulkanFullScreenQuad
diff --git a/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.h b/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.h
index c99358cb8b..8710074656 100644
--- a/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.h
+++ b/subprojects/gst-plugins-bad/gst-libs/gst/vulkan/gstvkfullscreenquad.h
@@ -132,6 +132,9 @@ void                gst_vulkan_full_screen_quad_set_blend_factors   (GstVulkanFu
                                                                      VkBlendFactor dst_blend_factor,
                                                                      VkBlendFactor src_alpha_blend_factor,
                                                                      VkBlendFactor dst_alpha_blend_factor);
+GST_VULKAN_API
+void                gst_vulkan_full_screen_quad_enable_clear        (GstVulkanFullScreenQuad * self,
+                                                                     gboolean enable_clear);
 
 GST_VULKAN_API
 gboolean            gst_vulkan_full_screen_quad_prepare_draw        (GstVulkanFullScreenQuad * self, GstVulkanFence * fence, GError ** error);