From 55fa0a54a2c421272d9f9a8638aaa29940e2b1f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Sun, 12 Jan 2025 12:44:29 +0200
Subject: [PATCH] video-overlay-composition: Handle the SCALE meta
 transformation

Simply update the render rectangle according to the scale factor. As only the
render rectangle is changed, the seqnum of the rectangle stays intact and no
additional GPU uploads are necessary.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8288>
---
 .../gst/video/video-overlay-composition.c     | 67 ++++++++++++++++---
 1 file changed, 57 insertions(+), 10 deletions(-)

diff --git a/subprojects/gst-plugins-base/gst-libs/gst/video/video-overlay-composition.c b/subprojects/gst-plugins-base/gst-libs/gst/video/video-overlay-composition.c
index 79042f58dc..e69a14f973 100644
--- a/subprojects/gst-plugins-base/gst-libs/gst/video/video-overlay-composition.c
+++ b/subprojects/gst-plugins-base/gst-libs/gst/video/video-overlay-composition.c
@@ -212,20 +212,67 @@ gst_video_overlay_composition_meta_transform (GstBuffer * dest, GstMeta * meta,
   smeta = (GstVideoOverlayCompositionMeta *) meta;
 
   if (GST_META_TRANSFORM_IS_COPY (type)) {
-    GstMetaTransformCopy *copy = data;
+    GST_DEBUG ("copy video overlay composition metadata");
 
-    if (!copy->region) {
-      GST_DEBUG ("copy video overlay composition metadata");
+    dmeta =
+        (GstVideoOverlayCompositionMeta *) gst_buffer_add_meta (dest,
+        GST_VIDEO_OVERLAY_COMPOSITION_META_INFO, NULL);
+    if (!dmeta)
+      return FALSE;
 
-      /* only copy if the complete data is copied as well */
-      dmeta =
-          (GstVideoOverlayCompositionMeta *) gst_buffer_add_meta (dest,
-          GST_VIDEO_OVERLAY_COMPOSITION_META_INFO, NULL);
-      if (!dmeta)
-        return FALSE;
+    dmeta->overlay = gst_video_overlay_composition_ref (smeta->overlay);
+  } else if (GST_VIDEO_META_TRANSFORM_IS_SCALE (type)) {
+    GstVideoMetaTransform *trans = data;
+    GstVideoOverlayComposition *new_comp;
+    gint ow, oh, nw, nh;
+    guint n_rectangles;
 
-      dmeta->overlay = gst_video_overlay_composition_ref (smeta->overlay);
+    ow = GST_VIDEO_INFO_WIDTH (trans->in_info);
+    nw = GST_VIDEO_INFO_WIDTH (trans->out_info);
+    oh = GST_VIDEO_INFO_HEIGHT (trans->in_info);
+    nh = GST_VIDEO_INFO_HEIGHT (trans->out_info);
+
+    GST_DEBUG ("scaling video overlay composition metadata %dx%d -> %dx%d", ow,
+        oh, nw, nh);
+
+    smeta = (GstVideoOverlayCompositionMeta *) meta;
+
+    new_comp = gst_video_overlay_composition_new (NULL);
+    n_rectangles = gst_video_overlay_composition_n_rectangles (smeta->overlay);
+    for (guint i = 0; i < n_rectangles; i++) {
+      GstVideoOverlayRectangle *rect =
+          gst_video_overlay_composition_get_rectangle (smeta->overlay, i);
+      GstVideoOverlayRectangle *new_rect =
+          gst_video_overlay_rectangle_copy (rect);
+      gint render_x = 0, render_y = 0;
+      gint new_render_x, new_render_y;
+      guint render_width = 0, render_height = 0;
+      guint new_render_width, new_render_height;
+
+      gst_video_overlay_rectangle_get_render_rectangle (rect, &render_x,
+          &render_y, &render_width, &render_height);
+
+      new_render_x = (render_x * nw) / ow;
+      new_render_y = (render_y * nw) / ow;
+      new_render_width = (render_width * nw) / ow;
+      new_render_height = (render_height * nw) / ow;
+
+      GST_DEBUG
+          ("overlay rectangle %u (seqnum: %d) (%dx%d)x(%ux%u) -> (%dx%d)->(%ux%u)",
+          i, gst_video_overlay_rectangle_get_seqnum (rect), render_x, render_y,
+          render_width, render_height, new_render_x, new_render_y,
+          new_render_width, new_render_height);
+
+      gst_video_overlay_rectangle_set_render_rectangle (new_rect,
+          new_render_x, new_render_y, new_render_width, new_render_height);
+      gst_video_overlay_composition_add_rectangle (new_comp, new_rect);
+      gst_video_overlay_rectangle_unref (new_rect);
     }
+
+    dmeta = gst_buffer_add_video_overlay_composition_meta (dest, new_comp);
+    gst_video_overlay_composition_unref (new_comp);
+    if (!dmeta)
+      return FALSE;
   } else {
     /* return FALSE, if transform type is not supported */
     return FALSE;