Re: Alpha in Pango Color

[Behdad Esfahbod <behdad esfahbod gmail com>]

Hi William,

Currently Pango doesn't support alpha in colors.  At this point, it might make
sense to add a separate PANGO_ATTR_ALPHA, instead of an RGBA type.

I'd take a patch.  Matthias, is this something you can possibly implement?
Shouldn't take long to implement and test...

b

On 15-08-08 01:10 AM, William Kappler wrote:
> Hello,
>
> I am seeking a way to encode the alpha channel of color into text, so that it
> can vary within a Pango layout like color. As far as I can tell, this is not
> supported directly by Pango. If I set an alpha via *cairo_set_source_rgba()*
> there is no way to later change it: the markup only offers 3-component hex
> colors.
>
> I took a brief look at the source and it seems a non-trivial matter to add
> such functionality. I was unable to trace down where exactly the color
> attribute ends up affecting the text color. As I said, though, this was a
> brief look.
>
> Ideally, *foreground* and *background* would take both three-component and
> four-component colors (#NNNNNN or #NNNNNNNN), but an additional alpha tag
> would be an option as well.
>
> I ask because I am currently attempting to apply Pango-Cairo as the text
> rendering engine in an open source game engine I am working on. I figure alpha
> has little impact on most of Pango's applications - but in the context of 3D,
> it is quite important.
>
> Does anyone have any thoughts or advice on this topic? I would be willing to
> write a patch to this effect if that is of interest.
>
> :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-
> William E. Kappler II
> LinkedIn <https://www.linkedin.com/in/williamkappler> · Blog
> <http://williamkappler.blogspot.com/> · Project Website
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>
>
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