Giving up for now

[Roderick Colenbrander]

On Sat, May 2, 2009 at 11:18 PM, Joel Holdsworth
<joel at airwebreathe.org.uk> wrote:
> On Sat, 2009-05-02 at 22:56 +0200, Roderick Colenbrander wrote:
>> On Sat, May 2, 2009 at 8:57 PM, Joel Holdsworth
>> <joel at airwebreathe.org.uk> wrote:
>> > On Sat, 2009-05-02 at 20:38 +0200, Roderick Colenbrander wrote:
>> >> On Sat, May 2, 2009 at 6:55 PM, Joel Holdsworth
>> >> <joel at airwebreathe.org.uk> wrote:
>> >> > Hi All,
>> >> >
>> >> > I've hit a bit of a wall with alpha blended icons. CreateIcon is working
>> >> > fine for icon creation, but ExtractIcon and LoadIconFromResource etc.
>> >> > are all proving more of a problem. All of these use various GDI DIB
>> >> > functions to coerce the icon bitmap to the correct colour depth and
>> >> > size. The problem is that preserving the alpha channel through these DIB
>> >> > functions seems to be impossible because they go via X11, so until the
>> >> > dib engine is merged (after hell freezes over) I'm not sure I can go
>> >> > much further.
>> >> >
>> >> > Joel
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >>
>> >> If you say X11 might be problematic note that more and more display
>> >> drivers are offering visuals with alpha, so 32-bit ones instead of
>> >> 24-bit. You could force the selection of such a visual in winex11.drv
>> >> for testing.
>> >>
>> >> Roderick
>> >
>> > Is that right? I simply assumed it would screw it up. If the problem can
>> > be solved with fixes to user32 or gdi32, then I can probably find the
>> > solution. If it involves work on winex11, then I'm not really the right
>> > guy for the job.
>> >
>> >
>> >
>>
>> Why again did you need this specific alphablend method? The icon can't
>> be converted to use some basic color keying for transparency or so?
>
> The reason is that the outlines will look aliased, and there will be no
> drop-shadows - without alpha the Tango icons won't look better than the
> current set. Also, I figured that icon rendering should be fixed for the
> sake of wine as a whole - which I think it should. It seems like a good
> little task for a wine beginner, and indeed I've made a lot of progress
> - I'm just a bit stuck.
>
> The culprit is a transfer through StretchDIBits in user32 which strips
> the alpha channel. I can't see a way round it - using StretchBlt doesn't
> help, and neither does GdiTransparentBlt.
>
> Another insentive: I suspect fixing this would also fix bug #201 which
> is now over 8 years old!
>
>
>

I just looked a little more into it. As you mentioned StretchDIBits in
user32 removes the alpha channel. According to this post at MSDN
(http://msdn.microsoft.com/en-us/library/dd145023(VS.85).aspx) the
function got extended in Vista to include PNG support because PNG is
used for most icons in Vista. It might be useful to check that out.
The page mentions it was meant for printers but most likely they also
use this for icon rendering. I think it can be used in cooperation
with XRender (there are various xrender examples for dealing with
alpha).

Roderick