Bert Freudenberg wrote:
>
> On 28.03.2009, at 13:31, Juan Vuletich wrote:
>
>> Damien Cassou wrote:
>>> On Fri, Mar 27, 2009 at 9:16 PM, Juan Vuletich <juan at jvuletich.org> 
>>> wrote:
>>>
>>>> I'm pleased to announce that Cuis is available. Cuis is a Squeak
>>>> distribution with emphasis on simplicity. You can download it from
>>>> http://www.jvuletich.org/Cuis/Cuis1.0-0158.zip . The web is not 
>>>> done yet.
>>>>
>>>
>>> The content looks very ugly when using a composite window manager (I'm
>>> on Ubuntu with Compiz). When switching off compiz, things looks ok.
>>>
>>>
>> If I remeber correctly, these kind of problems also happened with 
>> other Squeak distributions and was due to a kind of bug in BitBlt, 
>> right?
>
> Not a BitBlt bug, but how BitBlt is used. If all drawing operations 
> would set the Display's alpha component to 1 then it would be fully 
> opaque.
>
It is a BitBlt bug. Evaluate and print this:

f1 _ Form extent: 8 at 8 depth: 32.
f1 fillColor: (Color r: 1.0 g: 1.0 b: 0.7 alpha: 0.6).
f2 _ Form extent: 8 at 8 depth: 32.
f2 fillColor: (Color r: 0.5 g: 1.0 b: 0.7 alpha: 0.7).
bb _(BitBlt toForm: f1) sourceForm: f2; combinationRule: 28; copyBits.
f1 display.
(f1 colorAt: 2 at 2) alpha

Rule 28 is rgbMin. The resulting color should be (Color r: 0.5 g: 1.0 b: 
0.7 alpha: 0.6). But alpha is set to zero. This is a bug, and it is what 
causes wrong alpha values in Display in Cuis.
>> Is it this problem http://bugs.squeak.org/view.php?id=7068 ?
>
>
> It sounds like that's the one. Old Unix VMs do not ignore the alpha 
> channel of Display.
>
> - Bert -
>
>
I believe the best would be to honor the alpha channel, and be able to 
set it correctly.

Cheers,
Juan Vuletich