[cairo] cairo-1.10 regression?

[Julien Bramary]

Thank you very much for all the info!I will try the workaround in the meantime and stay tuned :)
Julien

> Date: Sat, 27 Nov 2010 11:42:35 +0100
> Subject: Re: [cairo] cairo-1.10 regression?
> From: ranma42 at gmail.com
> To: julien_bramary at msn.com
> CC: cairo at cairographics.org
> 
> On Fri, Nov 26, 2010 at 4:11 PM, Julien Bramary <julien_bramary at msn.com> wrote:
> > Hey guys,
> > I tried 1.10 today and found some odd glitches in my application. I narrowed
> > it down to a vertical and horizontal line crossing showing
> > strange artefacts.
> > The concerned lines either have a non-integer width or non-integer starting
> > and end points.
> > Here is the code snippet I used to test this (the code before that paints
> > the background to white):
> > layer_0 = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, 600, 600);
> > cairo_t *cr = cairo_create (layer_0);
> > cairo_set_source_rgb (cr, 1, 1, 1);
> > cairo_paint (cr);
> > double x = 50.323;
> > double y = 50.768;
> > cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
> > cairo_set_source_rgb (cr, 0.1f, 0.1f, 0.1f);
> > cairo_set_line_width (cr, 6);
> > cairo_move_to (cr, x, 0);
> > cairo_line_to (cr, x, 600);
> > cairo_move_to (cr, 0, y);
> > cairo_line_to (cr, 600, y);
> > cairo_stroke (cr);
> > The screenshots attached clearly show that 1.8.10 is doing the right thing
> > with the semi-transparent bits whereas 1.10.0 is not.
> > Anyone seen this with 1.10? I couldn't find related bugs in the tracker. I
> > just tried with latest Git version and it still happens.
> 
> I can confirm the problem. It is caused by a bug in the implementation of the
> rectilinear rasterizer.
> 
> A temporary workaround might be to avoid the rectilinear rasterizer, for
> example by adding a degenerate curve:
> 
> cairo_rel_curve_to (cr, 0, 0, 0, 0, 0, 0);
> 
> right before stroking.
> 
> I'm working on fixing the implementation, but it will probably require some
> nontrivial changes to the rectilinear rasterizer.
> 
> Andrea
 		 	   		  
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