Re: Re: Re: Re: Re: Getting a Cairo context

[Lucas Levrel <llevrel yahoo fr>]

Le 26 mars 2015, Emmanuele Bassi a écrit :

> > What I do in a similar situation is keeping a kind of carbon copy of the
> > bare drawing:
> >
> > - get two pixmaps from the drawing area :
> >   bare_pixmap=gdk_pixmap_new(d_area->window,width,height,-1);
> >   full_pixmap=gdk_pixmap_new(d_area->window,width,height,-1);
> >
> > - draw your "background" on bare_pixmap
> >
> > - when you have to redraw, just copy bare_pixmap to full_pixmap, add stuff
> >   to full_pixmap, then display it:
> >
> >   gdk_draw_drawable(full_pixmap,copy_gc,bare_pixmap,0,0,0,0,-1,-1);
> >   (add stuff to full_pixmap)
> >   gdk_draw_drawable(d_area->window, copy_gc, full_pixmap, x, y, x, y, width,
> > height);
> >
> > Where copy_gc has been defined this way:
> >   GdkGC *copy_gc=d_area->style->fg_gc[GTK_WIDGET_STATE (d_area)];
>
> This is really GTK+ 2.x only, and even then it's pretty much X11-only.

It works in Windows, cross-compiled in Linux with "mxe" (MinGW cross env).

> Pixmaps are really Cairo surfaces, these days, and GCs are Cairo
> contexts. The widget state is part of the GtkStyleContext, and the
> gtk_render_* API substitute the background rendering. Even for GTK+
> 2.x API you should not be using gdk_draw_* and GdkGC API at all,
> unless your code is supposed to work with GTK+ 2.6.

It is supposed to use the latest GTK+ 2 (2.24 I guess).

I'm eager to read a tutorial on GTK2 programming. I think I never found 
one, so I'm using the reference manuals, which is a rather tough way to 
learn indeed. (gtk-demo doesn't have examples of what I need)

Your help is appreciated.

--
Lucas Levrel