On 4 February 2015 at 12:40, Guillaume van Baalen <postdo...@yahoo.fr> wrote: > I think I found the problem (or at least a workaround). > > If the Cairo context $cr in the expose_event sub is a global variable, I get > an X error crash. If I set it to be local to the sub, as in the code at the > end of this message, I don't get an X error anymore, and a consistent > behaviour across systems. > > I can live with that, but am still wondering why I get an error if $cr is > global... > > Also in case it helps and for future reference, I was able to get some > backtrace by breaking on _XError:
AFAIC a cairo context is created for each paint call... So the CairoContext tends to be unique or each draw cycle. https://developer.gnome.org/gdk2/stable/gdk2-Cairo-Interaction.html#gdk-cairo-create "Note that due to double-buffering, Cairo contexts created in a GTK+ expose event handler cannot be cached and reused between different expose events. " https://developer.gnome.org/gdk3/stable/gdk3-Cairo-Interaction.html#gdk-cairo-create "A newly created Cairo context. Free with cairo_destroy() when you are done drawing." https://developer.gnome.org/gtk3/stable/chap-drawing-model.html#hierarchical-drawing "During the Paint phase we will send a single expose event to the toplevel window. The event handler will create a cairo context for the window and emit a GtkWidget::draw() signal on it, which will propagate down the entire widget hierarchy in back-to-front order, using the clipping and transform of the cairo context. This lets each widget draw its content at the right place and time, correctly handling things like partial transparencies and overlapping widgets. " _______________________________________________ gtk-perl-list mailing list gtk-perl-list@gnome.org https://mail.gnome.org/mailman/listinfo/gtk-perl-list
