[cairo] create an image from window for printing

[Owen Taylor]

Hmm, it just occurred to me that there was a small bit of nonsense
in my examples:

On Sat, 2007-01-20 at 17:50 -0500, Owen Taylor wrote:

> So, say you have an surface of dimensions w0, h0, and you want to draw
> it at x,y and size w,h 
> 
>  cairo_save(cr);
>  cairo_move_to(cr, x, y);
         ^^^^^^^
         translate

>  cairo_scale(cr, w/w0, h/h0);
>  cairo_set_source_surface(cr, surface, 0, 0);
>  cairo_paint(cr);
> 
> You really should study that until you realize that there is zero magic
> in it; it's just a straightforward consequence of how cairo works.
>
> So, say if you were drawing directly to a PDF surface, and you wanted to
> paint it with the top left at 1cm, 1cm and with width of 10cm, then you
> would do:
> 
>  #define POINTS_PER_CM (72. / 2.54);
> 
>  cairo_save(cr);
>  cairo_move_to(cr, POINTS_PER_CM, POINTS_PER_CM);
         ^^^^^^^
         translate
>  double scale = (10 * POINTS_PER_CM) / w0;
>  cairo_scale(cr, scale, scale); /* Preserve aspect ratio */
>  cairo_set_source_surface(cr, surface, 0, 0);
>  cairo_paint(cr);

Sorry for any confusion,
						Owen