examples: overlay: Add an example for Win32 window handle with playbin

Demonstrate video overlay handling on Windows when playbin is in use

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/983>

tests/examples/overlay/meson.build

@@ -43,4 +43,11 @@ if host_system == 'windows'
     dependencies : [gst_dep, video_dep],
     install: false,
   )
+
+  executable('win32-videooverlay-playbin', 'win32-videooverlay-playbin.c',
+    c_args : gst_plugins_base_args,
+    include_directories : [configinc, libsinc],
+    dependencies : [gst_dep, video_dep],
+    install: false,
+  )
 endif

tests/examples/overlay/win32-videooverlay-playbin.c

@@ -0,0 +1,249 @@
+/*
+ * GStreamer
+ * Copyright (C) 2020 Seungha Yang <seungha@centricular.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gst/gst.h>
+#include <gst/video/videooverlay.h>
+#include <windows.h>
+
+static GMainLoop *loop = NULL;
+static gboolean visible = FALSE;
+static HWND hwnd = NULL;
+static gboolean set_handle_on_request = FALSE;
+
+static LRESULT CALLBACK
+window_proc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
+{
+  switch (message) {
+    case WM_DESTROY:
+      hwnd = NULL;
+
+      if (loop) {
+        g_main_loop_quit (loop);
+      }
+      return 0;
+    default:
+      break;
+  }
+
+  return DefWindowProc (hWnd, message, wParam, lParam);
+}
+
+static gboolean
+msg_cb (GIOChannel * source, GIOCondition condition, gpointer data)
+{
+  MSG msg;
+
+  if (!PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
+    return G_SOURCE_CONTINUE;
+
+  TranslateMessage (&msg);
+  DispatchMessage (&msg);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+bus_msg (GstBus * bus, GstMessage * msg, gpointer user_data)
+{
+  GstElement *playbin = GST_ELEMENT (user_data);
+
+  switch (GST_MESSAGE_TYPE (msg)) {
+    case GST_MESSAGE_ASYNC_DONE:
+      /* make window visible when we have something to show */
+      if (!visible && hwnd) {
+        ShowWindow (hwnd, SW_SHOW);
+        visible = TRUE;
+      }
+
+      gst_element_set_state (playbin, GST_STATE_PLAYING);
+      break;
+    case GST_MESSAGE_EOS:
+      gst_println ("End of stream");
+      g_main_loop_quit (loop);
+      break;
+    default:
+      break;
+  }
+
+  return TRUE;
+}
+
+static GstBusSyncReply
+bus_sync_handler (GstBus * bus, GstMessage * msg, gpointer user_data)
+{
+  if (set_handle_on_request &&
+      gst_is_video_overlay_prepare_window_handle_message (msg)) {
+    GstVideoOverlay *overlay = GST_VIDEO_OVERLAY (GST_MESSAGE_SRC (msg));
+
+    gst_println ("Pipeline needs window handle");
+    gst_video_overlay_set_window_handle (overlay, (guintptr) hwnd);
+    gst_message_unref (msg);
+
+    return GST_BUS_DROP;
+  }
+
+  switch (GST_MESSAGE_TYPE (msg)) {
+    case GST_MESSAGE_ERROR:{
+      GError *err;
+      gchar *dbg;
+
+      gst_message_parse_error (msg, &err, &dbg);
+      gst_printerrln ("ERROR %s ", err->message);
+      if (dbg != NULL)
+        gst_printerrln ("ERROR debug information: %s", dbg);
+      g_clear_error (&err);
+      g_free (dbg);
+
+      g_main_loop_quit (loop);
+      break;
+    }
+    default:
+      break;
+  }
+
+  return GST_BUS_PASS;
+}
+
+gint
+main (gint argc, gchar ** argv)
+{
+  GstElement *playbin;
+  WNDCLASSEX wc = { 0, };
+  HINSTANCE hinstance = GetModuleHandle (NULL);
+  GIOChannel *msg_io_channel;
+  GOptionContext *option_ctx;
+  GError *error = NULL;
+  gchar *uri = NULL;
+  RECT wr = { 0, 0, 320, 240 };
+  gint exitcode = 0;
+  gboolean ret;
+  GOptionEntry options[] = {
+    {"uri", 0, 0, G_OPTION_ARG_STRING, &uri,
+        "URI to test playback with Win32 overlay", NULL}
+    ,
+    {"set-handle-on-request", 0, 0, G_OPTION_ARG_NONE, &set_handle_on_request,
+        "Set window handle on \"prepare-window-handle\" message", NULL}
+    ,
+    {NULL}
+  };
+
+  option_ctx =
+      g_option_context_new ("WIN32 video overlay with playbin example");
+  g_option_context_add_main_entries (option_ctx, options, NULL);
+  g_option_context_add_group (option_ctx, gst_init_get_option_group ());
+  ret = g_option_context_parse (option_ctx, &argc, &argv, &error);
+  g_option_context_free (option_ctx);
+
+  if (!ret) {
+    gst_printerrln ("option parsing failed: %s", error->message);
+    g_clear_error (&error);
+    exit (1);
+  }
+
+  if (!uri) {
+    gst_printerrln ("--uri is a required argument");
+    g_clear_error (&error);
+    exit (1);
+  }
+
+  /* prepare window */
+  wc.cbSize = sizeof (WNDCLASSEX);
+  wc.style = CS_HREDRAW | CS_VREDRAW;
+  wc.lpfnWndProc = (WNDPROC) window_proc;
+  wc.hInstance = hinstance;
+  wc.hCursor = LoadCursor (NULL, IDC_ARROW);
+  wc.lpszClassName = "GstWin32VideoOverlayPlaybin";
+  RegisterClassEx (&wc);
+
+  AdjustWindowRect (&wr, WS_OVERLAPPEDWINDOW, FALSE);
+  hwnd = CreateWindowEx (0, wc.lpszClassName,
+      "GstWin32VideoOverlayPlaybin",
+      WS_CLIPSIBLINGS | WS_CLIPCHILDREN | WS_OVERLAPPEDWINDOW,
+      CW_USEDEFAULT, CW_USEDEFAULT,
+      wr.right - wr.left, wr.bottom - wr.top, (HWND) NULL, (HMENU) NULL,
+      hinstance, NULL);
+
+  loop = g_main_loop_new (NULL, FALSE);
+  msg_io_channel = g_io_channel_win32_new_messages (0);
+  g_io_add_watch (msg_io_channel, G_IO_IN, msg_cb, NULL);
+
+  /* prepare the pipeline */
+  playbin = gst_element_factory_make ("playbin", NULL);
+
+  if (!playbin) {
+    gst_printerrln ("playbin is not available");
+
+    exitcode = 1;
+    goto terminate;
+  }
+
+  /* User can set window handle on playbin before starting
+   * pipeline without watching "prepare-window-handle" message,
+   * because playbin/playsink will pass the given handle to selected
+   * video sink element later once video sink is prepared.
+   *
+   * But in case that an application wants to delay setting window handle
+   * as much as possible for some reason, the application needs to check
+   * "prepare-window-handle" message
+   * (use gst_is_video_overlay_prepare_window_handle_message() API for check)
+   * via a *sync* message handler and should set window handle on
+   * the *sync* message handler immediately */
+  if (!set_handle_on_request) {
+    GstVideoOverlay *overlay = GST_VIDEO_OVERLAY (playbin);
+
+    gst_println ("Setting window handle now");
+    gst_video_overlay_set_window_handle (overlay, (guintptr) hwnd);
+  } else {
+    gst_println ("Will set window handle on \"prepare-window-handle\" message");
+  }
+
+  g_object_set (playbin, "uri", uri, NULL);
+  gst_bus_set_sync_handler (GST_ELEMENT_BUS (playbin),
+      bus_sync_handler, NULL, NULL);
+  gst_bus_add_watch (GST_ELEMENT_BUS (playbin), bus_msg, playbin);
+
+  if (gst_element_set_state (playbin,
+          GST_STATE_PAUSED) == GST_STATE_CHANGE_FAILURE) {
+    gst_printerrln ("Pipeline doesn't want to pause");
+    gst_bus_remove_watch (GST_ELEMENT_BUS (playbin));
+
+    exitcode = 1;
+    goto terminate;
+  }
+
+  g_main_loop_run (loop);
+  gst_element_set_state (playbin, GST_STATE_NULL);
+  gst_bus_remove_watch (GST_ELEMENT_BUS (playbin));
+
+terminate:
+  if (hwnd)
+    DestroyWindow (hwnd);
+
+  gst_object_unref (playbin);
+  g_io_channel_unref (msg_io_channel);
+  g_main_loop_unref (loop);
+  g_free (uri);
+
+  return exitcode;
+}