Re: mono, gray and index configs

["Antonino A. Daplas" <adaplas@gmail.com>]

Geert Uytterhoeven wrote:
> On Thu, 11 Aug 2005, Antonino Daplas wrote:
>> On 8/11/05, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>>> On Thu, 11 Aug 2005, Antonino A. Daplas wrote:
>>>> that all the lengths = 1 and offsets = 0.  Currently, we have no way to
>>>> specifically request for mono01, mono10, or 1-bit pseudocolor. Just check
>>>> for fix->visual afterwards.
>>> For mono01 or mono10, if the visual is pseudocolor, just set the colormap to
>>> black/white or white/black.
>> I don't know. If I can change the colormap, I would  advertise this as
>> 1-bit pseudocolor, not monochrome.  Otherwise, why differentiate
>> between mono01 and mono10 if I can control what color is 0 and what
>> color is 1.  I think the closest definition of monochrome is 1-bit
>> static pseudocolor.  And we just have mono01 and mono10 to advertise
>> how hardware treats 0/1 (background/foreground or reverse).
> 
> Yes, for advertisement, that's true (cfr. amifb with bpp = 1, which is
> pseudocolor).
> 

Ok.

> But when the app needs monochrome, it can ask for 1 bpp. If it returns a mono
> visual, fine. If it returns a pseudocolor visual, set the colormap to
> black/white.
> 
>> I have a few things that are still not clear to me.  If I understand
>> it correctly, monochrome means 2 colors regardless of the bit depth. 
> 
> Monochrome means 2 colors, which are black and white (or white and black). If
> the colors are different, it's (static) pseudocolor.
> 
> In fact monochrome is a special case of static pseudocolor.

Ok.

> 
>> So it's possible, for example, to have 8-bit monochrome that has only
>> two colors, ie 0x00 and 0xff.   If this was 8-bit static pseudocolor,
> 
> Yes, cfr. old HP9000/300 graphics hardware.
> 

Hmm.  Yes, there's a bug in fbdev then with regards to this hardware.

>> then it has 256 different colors.
> 
> Yes.
> 
>> (Depending on how correct I am with the interpretation, there might be
>> some bugs in fbdev on how it determines the color depth. No one is
>> complaining yet though, so greater than 1-bit monochrome is probably
>> rare if not nonexistent.)
> 
> There definitely are bugs w.r.t. this, especially in the 2.4 logo code ;-)
> 

Yes, I would agree.  Do you know of any outstanding bugs on color handling
in 2.6 code, especially for hardware with bitdepths < 8? I would like to
fix them.

Tony


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