Re: drawing moving shapes

[Michael Torrie <torriem chem byu edu>]

On Fri, 2007-02-02 at 18:01 -0700, Rob Barnes wrote:
> It seems to work fine without using g_idle and just using
> gdk_threads_enter()/gdk_threads_leave(). What do I gain from using g_idle?

Well you gain simplicity, and you can avoid the gdk locking stuff.  Also
on some platforms, particularly win32, you just cannot call gdk or gtk
functions from a thread, even with the locking primitives due to the way
the win32 message events work.

The theoretically correct way to interact with the gui is either with
g_idle_add (thread-safe), or with some kind of IPC mechanism where other
threads can queue up events that you feed into the main loop.

Michael


> Thanks.
>
> -RobB
>
> Michael
> > > Some code snippets:
> > >
> > > GtkWidget *drawing_area;
> > > ....
> > > //Inside main:
> > > drawing_area = gtk_drawing_area_new ();
> > > g_signal_connect (G_OBJECT (drawing_area), "expose_event", G_CALLBACK
> > > (expose_event), NULL);
> > > gtk_widget_set_events(drawing_area,GDK_ALL_EVENTS_MASK);
> > > ....
> > >
> > > gboolean expose_event( GtkWidget      *widget,
> > >                               GdkEventExpose *event )
> > > {
> > > printf("expose\n");
> > >     //draw_player(players[0]);
> > >   gdk_draw_drawable (widget->window,
> > >              widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
> > >              pixmap,
> > >              event->area.x, event->area.y,
> > >              event->area.x, event->area.y,
> > >              event->area.width, event->area.height);
> > >
> > >   return FALSE;
> > > }
> > >
> > > //Inside a asynchronous function
> > > //marker is an ADT
> > > gdk_draw_polygon (pixmap,marker.kontext,TRUE,marker->poly,4);
> > > ....
> > > gdk_widget_queue_draw(drawing_area);
> > > ....
> > >
> > > Thanks.
> > > -RobB
> > >
> > >
> > > On 2/2/07, Michael Ekstrand <mekstran scl ameslab gov> wrote:
> > > > On Fri, 2007-02-02 at 12:20 -0700, Rob Barnes wrote:
> > > > > I'm trying to write a simple program that draws a moving polygon on
> > the
> > > > > screen. I started with the scribble-simple example and modified to
> > draw
> > > > the
> > > > > moving shape by redrawing the shape in the background color in the
> > > > previous
> > > > > position first then drawing it in the foreground color in the
> > current
> > > > > position. It works fine, except it only refreshes when something
> > happens
> > > > > such as mouse movement, click, expose, window adjustment. So to keep
> > > > things
> > > > > moving I have to keep moving the mouse around, but it stops if the
> > mouse
> > > > > stops, even though the polygon is being redrawn contently.
> > > >
> > > > Make sure you request a redraw every time the underlying state changes
> > -
> > > > check out gtk_widget_queue_draw.
> > > >
> > > > --
> > > > Michael Ekstrand
> > > > Research Assistant, Scalable Computing Laboratory
> > > > Goanna, compute cluster and InfiniBand network monitor tool:
> > > >         http://www.scl.ameslab.gov/Projects/Monitor/
> > > _______________________________________________
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> > > gtk-app-devel-list gnome org
> > > http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
> >
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