Re: deprecated gtk_cairo_create

[Jim Charlton <charltn gmail com>]

On 2016-12-30 05:45 AM, Colomban Wendling wrote:
> 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.
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If one does want to draw into a cairo_surface_t, one can create a cairo 
context for drawing? E.g.

cairo_t <https://cairographics.org/manual/cairo-cairo-t.html#cairo-t>  *
cairo_create (/|cairo_surface_t 
<https://cairographics.org/manual/cairo-cairo-surface-t.html#cairo-surface-t> 
*target|/);

That use of cairo_create() is not deprecated... (I assume).

https://developer.gnome.org/gtk3/stable/ch01s05.html

jim...