Re: How to redraw the blanked section of a widget after a expose-event?

[Arto Karppinen <exeonical mail suomi net>]

krist misra wrote:
> Hi experts,
>
> I am using GTK+ and gstreamer to capture and show the video frames, I
> created a drawable widget using gtk_drawing_area_new() and using xvimage
> element of gstreamer to render the video, I also connected them by a
> gstreamer function gst_x_overlay_set_xwindow_id(), so the video frames
> rendered  by xvimage can show in the widget, now it works well.
>
> But I encounter a problem that if part of the drawable widget being covered
> by a menu or something, when the menu disappears, the covered section keeps
> blank, even other part of the widget still show the video.
>
> I try to write a function expose_cb() and connect it with the signal
> "expose-event", in that function I call gst_x_overlay_set_xwindow_id()
> again and also gtk_widget_show_all(), but it seems still not work. cos it's
> showing a video so I cannot save some image and redraw it again
> after it exposes.
>
> Anyone can help me? how should I do in the expose_cb or something else?
> Thanks a lot
> below is part of the source code
> -----------------------------------------------------------------------------------------
> static gboolean expose_cb(GtkWidget * widget, GdkEventExpose * event,
> gpointer data)
> {
>     gst_x_overlay_set_xwindow_id(GST_X_OVERLAY(data),
>                                   GDK_WINDOW_XWINDOW(widget->window));
>     gtk_widget_show_all(widget);
> }
>
> int main()
> {
> ...
>   gstreamer_main_video_image = gtk_drawing_area_new();
> ...
>   screen_sink = gst_bin_get_by_name (GST_BIN (appdata.bin), "screensink");
> ...
>   gst_x_overlay_set_xwindow_id(GST_X_OVERLAY(screen_sink),
>     GDK_WINDOW_XWINDOW(gstreamer_main_video_image->window));
>    g_signal_connect(gstreamer_main_video_image, "expose-event",
> G_CALLBACK(expose_cb),
>                              screen_sink);
>   gtk_widget_show_all(gstreamer_window);
> ...
> }
> ------------------------------------------------------------
> Krist.
> _______________________________________________
> gtk-app-devel-list mailing list
> gtk-app-devel-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
>
>   
I dont know if this is a correct solution, but i have drawn images to 
the background of gtk_drawing_area, and if you do that, then GTK will 
keep the background pixmap around for redrawing purposes.

Use something like this:

gdk_window_set_back_pixmap(widget->window, pixmap, FALSE);
gtk_widget_queue_draw_area(widget, 0, 0,
                          widget->allocation.width,
                          widget->allocation.height);

And create a pixmap where you draw the images, and queue redraw when the 
you redraw the pixmap.

--
Arto Karppinen
------------------------------
arto karppinen iki fi