[cairo] Subject: ImageSurfacePattern disappears with a large enough scale factor

[Michel Iwaniec]

Unfortunately, I just discovered that I declared victory too early. The patch you pushed merely seems to have reverted the situation to the one I had before upgrading my Ubuntu distribution. 

Rendering to an ImageSurface instead of my GtkDrawingArea still gives the same problem with the ImageSurfacePattern misaligning and eventually disappearing when scaled too much. Which again makes me wonder why the result from rendering to an ImageSurface can be so different from rendering to a GtkDrawingArea? Exactly what might differ in how cairo handles these targets?

I will try to create a repro case, but since I'm working on a closed-source application that I'm not allowed to share, it might take some time.

Regards,
Michel

--- On Fri, 10/31/08, Michel Iwaniec <michel_iwaniec at yahoo.com> wrote:

> From: Michel Iwaniec <michel_iwaniec at yahoo.com>
> Subject: Re: [cairo] Subject: ImageSurfacePattern disappears with a large enough scale factor
> To: "Chris Wilson" <chris at chris-wilson.co.uk>
> Cc: cairo at cairographics.org
> Date: Friday, October 31, 2008, 12:44 AM
> Thanks! After managing to manually overwrite all shared
> libraries and links to them, using this patched version
> worked like a charm. :)
> 
> Though I still have some problems with the grid and the
> image misaligning when zooming in *really* close. (much
> closer than in the linked .PNG images that is) I can live
> with that for now, but it would be nice if these precision
> errors(?) could be reduced even more.
> 
> Anyhow, thanks again for your über-fast solution! :)
> 
> // Michel
> 
> 
> --- On Thu, 10/30/08, Chris Wilson
> <chris at chris-wilson.co.uk> wrote:
> 
> > From: Chris Wilson <chris at chris-wilson.co.uk>
> > Subject: Re: [cairo] Subject: ImageSurfacePattern
> disappears with a large enough scale factor
> > To: michel_iwaniec at yahoo.com
> > Cc: cairo at cairographics.org
> > Date: Thursday, October 30, 2008, 11:17 PM
> > On Thu, 2008-10-30 at 15:02 -0700, Michel Iwaniec
> wrote:
> > > I seem to have run into some bug/precision limit
> in
> > Cairo when trying to upscale an ImageSurfacePattern
> too
> > much.
> > 
> > Interesting. I've just pushed a patch to git that
> > should reduce the
> > likelihood of overflow when scaling images. Can you
> try
> > testing the
> > current tip or can you post a test case for us to try?
> > Though in this
> > case, as you are upscaling, you may be underflowing
> the
> > pattern matrix
> > instead.
> > 
> > Thanks.
> > -- 
> > Chris