[cairo] create an image from window for printing

[Fabian Förg]

Owen Taylor wrote:
> 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
>
>   
Thanks for your help.

I changed my code to the following:
(The window which should be printed is in the struct appl_t).

static void draw_page(GtkPrintOperation * operation,
              GtkPrintContext * print_context, gint page_nr,
              appl_t * appl)
{
    GdkColor color;
    gdouble print_width, print_height, scale;
    gint width, height;
    cairo_t *cr, *cr_win;
    cairo_surface_t *surface;

    /* set background color of appl->window to white */
    color.red = 65535;
    color.green = 65535;
    color.blue = 65535;

    gtk_widget_modify_bg(appl->window, GTK_STATE_NORMAL, &color);

    /* get width and height of the appl->window */
    gdk_drawable_get_size(appl->window->window, &width, &height);

    /* create a surface of the appl->window */
    cr_win = gdk_cairo_create(appl->window->window);
    surface = cairo_get_target(cr_win);
    cairo_surface_reference(surface);
    cairo_destroy(cr_win);

    /* get width and heigth of print_context */
    print_width = gtk_print_context_get_width(print_context);
    print_height = gtk_print_context_get_height(print_context);

    /* transform the print_context into a cairo_context */
    cr = gtk_print_context_get_cairo_context(print_context);
   
    /* not needed ? */
    /*cairo_save(cr);
    cairo_translate(cr, 0., 0.);*/

    scale = (gdouble) print_width / width;

    /* scale, keep aspect ratio */
    cairo_scale(cr, scale, scale);

    cairo_set_source_surface(cr, surface, 0., 0.);
    cairo_surface_destroy(surface);

    cairo_paint(cr);
}


When I export it as PS, the PS-file looks as expected. However, when it 
is exported as PDF, the margins and the unneeded space are filled with 
"copies" of the captured window.
Is that a bug in the PDF export function?