Re: transparent cairo rendering

[Jose Hevia <jose francisco hevia gmail com>]

2009/6/18 Paul Davis <paul linuxaudiosystems com>:
> On Thu, Jun 18, 2009 at 11:30 AM, Jose
> Hevia<jose francisco hevia gmail com> wrote:
>> Hi, I have been fighting for a long time with a very simple program I
>> can't make work the way it should.
>>
>> The question is:
>>
>> Is that a bug or is it my fault?
>
> why are there calls to gtk_widget_show() from your expose handler?
>

:-)
Because I didn't know how to make it working, and gtk_widget_show
could send a sign to update the widget. It doesn't work without it
either.

As you can see, I used a rectangle too, in theory that is not
necessary, for the same reason, and disable the clipping mask too with
cairo_reset_clip, and set cairo_set_operator (cr, CAIRO_OPERATOR_OVER)
that is the default( theorically ).

I could make it work if I redraw manually(by a function copying
pixels) the surface, but this is not the way it should work, if cairo
uses hardware acceleration, I lost it.

here:
http://cairographics.org/operators/#clipmask

it says that source puts the alpha value and the color, this is not
what is doing. Seems like a bug to me.

Thanks for your help.