[mutter] screen-cast/src: Only allocate DMA buffers if other end supports it

[Marge Bot <marge-bot src gnome org>]

commit ca22622517c381a687e311b5eb8bf97c31140f5d
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Feb 1 18:33:35 2021 +0100

    screen-cast/src: Only allocate DMA buffers if other end supports it
    
    The other end of the PipeWire stream can set the buffer data type to a
    bitmask of supported buffer types. We should respect this, and not
    attempt to allocate a DMA buffer if it isn't asked for.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1697>

 src/backends/meta-screen-cast-stream-src.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)
---
diff --git a/src/backends/meta-screen-cast-stream-src.c b/src/backends/meta-screen-cast-stream-src.c
index 5d3440e5db..39c688d78e 100644
--- a/src/backends/meta-screen-cast-stream-src.c
+++ b/src/backends/meta-screen-cast-stream-src.c
@@ -747,10 +747,17 @@ on_stream_add_buffer (void             *data,
   spa_data[0].maxsize = stride * priv->video_format.size.height;
   spa_data[0].data = NULL;
 
-  dmabuf_handle =
-    meta_screen_cast_create_dma_buf_handle (screen_cast,
-                                            priv->video_format.size.width,
-                                            priv->video_format.size.height);
+  if (spa_data[0].type & (1 << SPA_DATA_DmaBuf))
+    {
+      dmabuf_handle =
+        meta_screen_cast_create_dma_buf_handle (screen_cast,
+                                                priv->video_format.size.width,
+                                                priv->video_format.size.height);
+    }
+  else
+    {
+      dmabuf_handle = NULL;
+    }
 
   if (dmabuf_handle)
     {
@@ -766,6 +773,13 @@ on_stream_add_buffer (void             *data,
     {
       unsigned int seals;
 
+      if (!(spa_data[0].type & (1 << SPA_DATA_MemFd)))
+        {
+          g_critical ("No supported PipeWire stream buffer data type could "
+                      "be negotiated");
+          return;
+        }
+
       /* Fallback to a memfd buffer */
       spa_data[0].type = SPA_DATA_MemFd;
       spa_data[0].flags = SPA_DATA_FLAG_READWRITE;