[gtk: 1/3] GtkMediaStream with gstreamer backend isn't 'prepared' until media is played

[Matthias Clasen <matthiasc src gnome org>]

commit 82f57c6a937a29911f879ffb9ef35eb1e1f48f46
Author: Caolán McNamara <caolanm redhat com>
Date:   Thu Feb 24 19:44:08 2022 +0000

    GtkMediaStream with gstreamer backend isn't 'prepared' until media is played
    
    This seems to be a problem since:
    https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/3565
    
    To demo the problem, the video demo in gtk4-demo is currently set to
    autoplay, but it doesn't autoplay on load as expected because the
    "prepared" notification doesn't fire until the user explicitly presses
    play.
    
    Similarly if the demo is tweaked to disable autoplay then on loading a
    video (or an audio-only ogg) the duration is not known or shown until
    the user presses play.
    
    In LibreOffice we want to know what the size of the video is to position
    it before the user can interact with it to set it to play. We can
    workaround this to some degree by listening to "invalidate-size" on the
    GtkMediaStream object which updates for videos, but that doesn't wor
    for audio-only streams.
    
    So restore listening to media-info-updated but ignore -1 (which I see
    for audio-only where I get -1 and then a useful value) and 0 of the
    original report.
    
    see also:
    https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/3550
    
    GNOME/gtk!4513

 modules/media/gtkgstmediafile.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
---
diff --git a/modules/media/gtkgstmediafile.c b/modules/media/gtkgstmediafile.c
index 0fead35bfa..58a8e5219f 100644
--- a/modules/media/gtkgstmediafile.c
+++ b/modules/media/gtkgstmediafile.c
@@ -172,6 +172,23 @@ gtk_gst_media_file_position_updated_cb (GstPlayer       *player,
   gtk_media_stream_update (GTK_MEDIA_STREAM (self), FROM_GST_TIME (time));
 }
 
+static void
+gtk_gst_media_file_media_info_updated_cb (GstPlayer          *player,
+                                          GstPlayerMediaInfo *media_info,
+                                          GtkGstMediaFile    *self)
+{
+  /* clock_time == 0: https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/1588
+   * GstPlayer's first media-info-updated comes with 0 duration
+   *
+   * click_time == -1: Seen on loading an audio-only ogg
+   */
+  GstClockTime clock_time = gst_player_media_info_get_duration (media_info);
+  if (clock_time == 0 || clock_time == -1)
+    return;
+
+  gtk_gst_media_file_ensure_prepared (self);
+}
+
 static void
 gtk_gst_media_file_seek_done_cb (GstPlayer       *player,
                                  GstClockTime     time,
@@ -219,6 +236,7 @@ gtk_gst_media_file_destroy_player (GtkGstMediaFile *self)
   if (self->player == NULL)
     return;
 
+  g_signal_handlers_disconnect_by_func (self->player, gtk_gst_media_file_media_info_updated_cb, self);
   g_signal_handlers_disconnect_by_func (self->player, gtk_gst_media_file_position_updated_cb, self);
   g_signal_handlers_disconnect_by_func (self->player, gtk_gst_media_file_end_of_stream_cb, self);
   g_signal_handlers_disconnect_by_func (self->player, gtk_gst_media_file_seek_done_cb, self);
@@ -237,6 +255,7 @@ gtk_gst_media_file_create_player (GtkGstMediaFile *file)
 
   self->player = gst_player_new (GST_PLAYER_VIDEO_RENDERER (g_object_ref (self->paintable)),
                                  gst_player_g_main_context_signal_dispatcher_new (NULL));
+  g_signal_connect (self->player, "media-info-updated", G_CALLBACK 
(gtk_gst_media_file_media_info_updated_cb), self);
   g_signal_connect (self->player, "position-updated", G_CALLBACK (gtk_gst_media_file_position_updated_cb), 
self);
   g_signal_connect (self->player, "end-of-stream", G_CALLBACK (gtk_gst_media_file_end_of_stream_cb), self);
   g_signal_connect (self->player, "seek-done", G_CALLBACK (gtk_gst_media_file_seek_done_cb), self);