From 14f6d9a53f5158eb81703b44b70f601c960d2b12 Mon Sep 17 00:00:00 2001
From: Philippe Normand <philn@igalia.com>
Date: Wed, 25 Dec 2024 15:04:03 +0100
Subject: [PATCH] wpevideosrc: Clear cached SHM buffers after caps
 re-negotiation

Otherwise buffers not corresponding to the negotiated caps might be pushed
downstream.

Fixes #4094

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8212>
---
 .../ext/wpe/gstwpethreadedview.cpp            | 31 +++++++++++++++++++
 .../ext/wpe/gstwpethreadedview.h              |  1 +
 .../ext/wpe/gstwpevideosrc.cpp                |  5 +++
 3 files changed, 37 insertions(+)

diff --git a/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.cpp b/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.cpp
index 05f16154b2..159a6c3acf 100644
--- a/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.cpp
+++ b/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.cpp
@@ -711,6 +711,37 @@ void GstWPEThreadedView::resize(int width, int height)
     });
 }
 
+void GstWPEThreadedView::clearBuffers()
+{
+  bool dispatchFrameComplete = false;
+  {
+    GMutexHolder lock(images_mutex);
+
+    if (shm.pending) {
+      auto meta = gst_buffer_get_video_meta(shm.pending);
+      if (static_cast<int>(meta->width) != wpe.width || static_cast<int>(meta->height) != wpe.height) {
+        gst_clear_buffer(&shm.pending);
+        dispatchFrameComplete = true;
+      }
+    }
+
+    if (shm.committed) {
+      auto meta = gst_buffer_get_video_meta(shm.committed);
+      if (static_cast<int>(meta->width) != wpe.width || static_cast<int>(meta->height) != wpe.height) {
+        gst_clear_buffer(&shm.committed);
+        dispatchFrameComplete = true;
+      }
+    }
+  }
+
+  if (dispatchFrameComplete) {
+    frameComplete();
+    // Wait until the next SHM buffer has been received.
+    threading.ready = false;
+    waitLoadCompletion();
+  }
+}
+
 void GstWPEThreadedView::frameComplete()
 {
     GST_TRACE("frame complete");
diff --git a/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.h b/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.h
index 7c5b578f1d..8e31aae3d4 100644
--- a/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.h
+++ b/subprojects/gst-plugins-bad/ext/wpe/gstwpethreadedview.h
@@ -45,6 +45,7 @@ public:
     void loadData(GBytes*);
     void runJavascript(const gchar*);
     void setDrawBackground(gboolean);
+    void clearBuffers();
 
     GstEGLImage* image();
     GstBuffer* buffer();
diff --git a/subprojects/gst-plugins-bad/ext/wpe/gstwpevideosrc.cpp b/subprojects/gst-plugins-bad/ext/wpe/gstwpevideosrc.cpp
index 90d385f303..ceb28ca6d3 100644
--- a/subprojects/gst-plugins-bad/ext/wpe/gstwpevideosrc.cpp
+++ b/subprojects/gst-plugins-bad/ext/wpe/gstwpevideosrc.cpp
@@ -329,6 +329,11 @@ gst_wpe_video_src_start (GstWpeVideoSrc * src)
     return FALSE;
   }
 
+  if (!created_view) {
+    GST_INFO_OBJECT (src, "Re-starting after re-negotiation, clearing cached SHM buffers");
+    src->view->clearBuffers ();
+  }
+
   GST_OBJECT_LOCK (src);
   bytes = src->bytes;
   src->bytes = NULL;