d3d12videosink: Present on GstVideoOverlay::expose()

... so that updated backbuffer can be swapped and presented

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7079>

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12videosink.cpp

@@ -1532,7 +1532,7 @@ gst_d3d12_video_sink_overlay_expose (GstVideoOverlay * overlay)
   auto self = GST_D3D12_VIDEO_SINK (overlay);
   auto priv = self->priv;
 
-  gst_d3d12_window_set_buffer (priv->window, nullptr);
+  gst_d3d12_window_expose (priv->window);
 }
 
 static void

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window-swapchain.cpp

@@ -585,6 +585,18 @@ SwapChain::present ()
   return GST_FLOW_OK;
 }
 
+void
+SwapChain::expose (GstD3D12Window * window)
+{
+  std::lock_guard <std::recursive_mutex> lk (lock_);
+  if (!resource_->swapchain || !resource_->cached_buf)
+    return;
+
+  auto ret = set_buffer (window, resource_->cached_buf);
+  if (ret == GST_FLOW_OK)
+    present ();
+}
+
 void
 SwapChain::before_rendering ()
 {

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window-swapchain.h

@@ -40,6 +40,7 @@ public:
   GstFlowReturn resize_buffer (GstD3D12Window * window);
   GstFlowReturn set_buffer (GstD3D12Window * window, GstBuffer * buffer);
   GstFlowReturn present ();
+  void expose (GstD3D12Window * window);
 
 private:
   void before_rendering ();

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window-win32.cpp

@@ -547,6 +547,14 @@ SwapChainProxy::present ()
   return sc->present ();
 }
 
+void
+SwapChainProxy::expose ()
+{
+  auto sc = get_swapchain ();
+  if (sc)
+    sc->expose (window_);
+}
+
 void
 HwndServer::register_window (GstD3D12Window * window)
 {

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window-win32.h

@@ -69,6 +69,7 @@ public:
   GstFlowReturn resize_buffer (INT width, INT height);
   GstFlowReturn set_buffer (GstBuffer * buffer);
   GstFlowReturn present ();
+  void expose ();
 
 private:
   std::shared_ptr<SwapChain> get_swapchain ();

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window.cpp

@@ -720,6 +720,16 @@ gst_d3d12_window_render (GstD3D12Window * self, SwapChainResource * resource,
   return GST_FLOW_OK;
 }
 
+void
+gst_d3d12_window_expose (GstD3D12Window * window)
+{
+  auto priv = window->priv;
+  auto proxy = priv->proxy.lock ();
+
+  if (proxy)
+    proxy->expose ();
+}
+
 GstFlowReturn
 gst_d3d12_window_set_buffer (GstD3D12Window * window, GstBuffer * buffer)
 {

subprojects/gst-plugins-bad/sys/d3d12/gstd3d12window.h

@@ -76,6 +76,8 @@ void             gst_d3d12_window_unlock    (GstD3D12Window * window);
 
 void             gst_d3d12_window_unlock_stop (GstD3D12Window * window);
 
+void             gst_d3d12_window_expose      (GstD3D12Window * window);
+
 GstFlowReturn    gst_d3d12_window_set_buffer (GstD3D12Window * window,
                                               GstBuffer * buffer);