[Xcb] xcb, xrender and thin lines

[Vincent Torri]

On Wed, 15 Feb 2006, Keith Packard wrote:

> On Wed, 2006-02-15 at 08:56 +0100, Vincent Torri wrote:
>
> > For the xlib engine, raster uses XRenderCompositeDoublePoly for drawaing
> > thin lines (and thin polygons too). That function is quite complicated and
> > maybe there is a better idea. Does someone as an idea about how to do that
> > with xcb, which maybe can be simpler ?
>
> Far worse than complicated, that function is horribly inadequate for the
> job of tesselating arbitrary polygons. I'm sorry I ever even considered
> putting that into the Xrender library. You should stop using it
> immediately to avoid catastrophe; it will generate garbage trapezoids
> for seemingly benign input. It barely supports the polygons that xclock
> generates, which was the only test application for that function.
>
> Generating trapezoids for arbitrary polygons is a hard problem; cairo
> still doesn't have a great algorithm in place for this (although we have
> read papers about which algorithm we should implement).

and any advices about doing line drawing with xrender ?

Vincent