[cairo] Draw a rectangle with dash lines

Jeff Muizelaar jeff at infidigm.net
Tue Feb 6 12:16:39 PST 2007


The patch looks basically correct to me. Unfortunately, it certainly
isn't elegant. I am not a huge fan of adding even more state to the mess
that is the stroker. Although, in this case, I didn't immediately see any
way to avoid adding state either.

At a minimum it would be good to see some more documentation added about
why this state is necessary etc.

Carl, when do you want to get the fix in by? If I have time I'll see if
we can improve the patch at all.

Jeff, if you could perhaps integrate some of your explanation of the
problem on bugzilla into the code that would help.

-Jeff

On Mon, Feb 05, 2007 at 04:16:37PM -0800, Jeff Smith wrote:
> I have just tracked down and sent in a patch for this bug (more info and patch in bugzilla).
> 
> https://bugs.freedesktop.org/show_bug.cgi?id=4863
> 
>  -- Jeff Smith
> 
> ----- Original Message ----
> From: Carl Worth <cworth at cworth.org>
> To: ken carlino <ken.carlino at gmail.com>
> Cc: cairo at cairographics.org
> Sent: Saturday, February 3, 2007 9:34:22 AM
> Subject: Re: [cairo] Draw a rectangle with dash lines
> 
> On Sat, 3 Feb 2007 00:27:18 -0600, "ken carlino" wrote:
> > It works in some cases, but in some cases, I see a rect with dash
> > lines and a filled triangle which covers half of the rect (from one
> > top corner to another bottom corner).
> 
> This is a fairly long-standing, (and very embarrassing), known bug.
> 
> Matthias Clasen first reported the bug sometime after the 1.0 release:
> 
>     stroking problems with wide dashed lines
>     https://bugs.freedesktop.org/show_bug.cgi?id=4863
> 
> And we added a test case for this to cairo's test suite, (leaky-dash).
> 
> It's obviously a quite nasty bug, (a drawing error that is effectively
> "infinite"). And before the 1.2 release we tried making all test suite
> failures go away.
> 
> This one though, we didn't have time to fix. So we made a conscious
> decision to release in spite of the known bug, (one comforting thing
> was that we at least hadn't seen a lot of duplicate reports).
> 
> Anyway, here I am caught with a duplicate report just before the 1.4
> release, and we still don't have the bug fixed.
> 
> If somebody wanted to try to track this down that would be very
> helpful. The way these kinds of bugs usually go is that there's a fair
> amount of work looking into exactly what happens. But once that work
> is done, actually fixing the bug isn't actually that hard.
> 
> So, I've never gotten around to the investigation part, but if someone
> else could help with this, that would be great.
> 
> -Carl
> 
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