Re: deprecated gtk_cairo_create

[Colomban Wendling <lists ban herbesfolles org>]

Hi,

Le 30/12/2016 à 12:20, Sergei Kolomeeyets a écrit :
> Hi, everyone
> […]
>
> {draw_callback}
>
> gboolean draw_callback(GtkWidget *area, GdkEventExpose *event, GArray
> *ptLinePoints) {

That's not the right signature for the GtkWidget::draw signal: it takes
a cairo_t* as the second parameter, not a GdkEventExpose like did
::expose.  And here you have your Cairo context :)

See
https://developer.gnome.org/gtk3/stable/GtkWidget.html#GtkWidget-draw [1]

Also, read
https://developer.gnome.org/gtk3/stable/ch26s02.html#id-1.6.3.4.11, and
more generally
https://developer.gnome.org/gtk3/stable/gtk-migrating-2-to-3.html

So basically you don't need gdk_cairo_create() at all.  If you want to
draw outside of the ::draw() handler and paint the cached thing then,
use a cairo_surface_t as the offscreen surface, and paint it then.

Hope this helps.

Cheers,
Colomban

[1] which says "CairoContext", but that's a weird lie on the API… not
sure why, maybe the GType has this name so introspection is confused.
Anyway, it's cairo_t.