[Render] Howto avoid black rect outside of the drawable when compositing?

[Soeren Sandmann]

Pierre-Loup Griffais <pgriffais at nvidia.com> writes:

> On Tuesday 15 July 2008 15:27:08 Clemens Eisserer wrote:
> > Hello,
> >
> > I am trying to draw a transformed image using XRender, which works
> > quite fine, however the problem I experience is that pixels which are
> > outside of the src-picture are rendered black:
> > http://picasaweb.google.com/linuxhippy/Transformations/photo#52233687016232
> >18514
> >
> > The XRender-protocol-spec says:
> > > When fetching pixels from the source or mask pictures, Render provides
> > > three options for pixel values which fall outside the drawable (this
> > > includes pixels within a window geometry obscured by other windows).
> > > +	Transparent.  Missing values are replaced with transparent.
> >
> > However I was not able to figure out howto set "it" to "transparent".
> > Any hints or ideas are really appreciated.
> 
> The spec says a lot of things...

Indeed.

> In practice your options for fetching outside a Picture are the various 
> repeatTypes (pictAttribs.repeat, bit CPRepeat):
> 
> > #define RepeatNone                          0
> > #define RepeatNormal                        1
> > #define RepeatPad                           2
> > #define RepeatReflect                       3
> 
> None of those allow you to do what you want; you'll need to use a mask with 
> the same transformation as your source Picture.

RepeatNone should result in pixels outside the window being treated as
transparent. If it doesn't, then that's a bug.


Soren