Re: drawing on offscreen surface

[Prasanta Sadhukhan <psadhukhan gmail com>]

On Fri, Aug 10, 2012 at 1:22 PM, Jean Brefort <jean brefort normalesup org> wrote:

This code is quite strange. Your call to cairo_set_source_surface() is
not useful since you use cairo_set_source_rgb() just after. You should
call cairo_paint() just after cairo_set_source_surface() if you want it
to have any effect.

If I do not call     cairo_set_source_rgb(cr, 0, 0, 1); how will get a blue rectangle?
Just having   these is giving me a window with black background.
cairo_set_source_surface(cr, surface, 0, 0);
cairo_rectangle(cr, 300,300, 200, 200);
cairo_stroke(cr);
cairo_paint(cr).

Can you please clarify?
As I told, I would like to get a blue rectangle in offscreen surface and a green rectangle in main visible surface so after final rendering of offscreen contents on main window, I would get both rectangles on main window.

Regards
Prasanta

Hope it helps,
Jean

Le vendredi 10 août 2012 à 13:07 +0530, Prasanta Sadhukhan a écrit :

> expose_event (GtkWidget *widget,GdkEventExpose *event, gpointer
> data)
> {
>   g_print("draw event main\n");
>
>   cairo_t *cr = gdk_cairo_create(widget->window);
> // draw blue rectangle into offscreen
>   cairo_set_source_surface(cr, surface, 0, 0);
>   cairo_set_source_rgb(cr, 0, 0, 1);
>   cairo_rectangle(cr, 300, 300, 200, 200);
>   cairo_stroke(cr);
>   cairo_paint(cr);
>
> //draw green rectangle onto main window
>     cairo_set_source_rgb(cr, 0, 1, 0);
>   cairo_rectangle(cr, 100, 100, 200, 200);
>    cairo_stroke(cr)
> }
>
>
>

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