Around 9 o'clock on Oct 23, Olivier Chapuis wrote:

> An application should query if the xserver has render support and if not
> take appropriate decisions. No? E.g., in FVWM we have a function which
> simulate XRenderComposite and a font spec can have two fonts one for Xft
> and an other one for core text rendering.

Client-side text is a powerful mechanism which is not easily replaced with
core fonts.  Xft uses the core protocol GetImage/PutImage when Render is
not available, but performance suffers greatly.  Applications like 
OpenOffice (and FrameMaker) are unable to provide reasonable text output 
with the core font primitives.  Client-side text is useful independently 
from anti-aliasing.

> In some case it is not the number of colors which counts but how the
> apps share the colours.

Our working assumption is that 8-bit PseudoColor displays are useful only
for legacy applications; those don't generally share well with others as 
they need custom or writable color values.  Any significant number of 
preallocated color cells generally cause these applications to fail.

> Moreover, if you use standard dithering methods, dithering is really really
> better in mode #5 and #6 than in the default mode.  So I think that

Render doesn't (currently) support dithering, and dithering to a random set
of colors is rather expensive.  I like having both a color cube and a gray 
ramp as I believe that provides more accurate anti-aliased text, I'm not 
sure how dithering fits into this model.

> Yes, using StaticColor is more or less equivalent than mode #6 (but
> with a bit different colours proportion (3/3/2) by default).

The new fb frame buffer code fits the largest color cube and fills the 
remaining entries with a gray ramp, precisely as you've described for mode 
#6.  PseudoColor with a completely allocated colormap is a poor substitute 
-- with StaticColor, the server will automatically fit new color requests 
into the existing color entries, while PseudoColor will fail the 
allocation request.

> I think a "full" mode does not hurt and assure backward compatibility.
> But, I do not care. I am more interested by mode #5.

Any PseudoColor mode which doesn't permit the bulk of legacy applications 
to run without problems isn't interesting in this context; it may be that 
the 'default' mode can allocate a few more colors than it does in current 
CVS, but I don't think it should use a 5x5x5 cube

> An other subject. Do you think that it is better to always use
> pow(2,k) grey colours (e.g., use 16 grey for the default in the place
> of the 21 grey) so that the grey are aligned with the 32x32x32 colour
> cube which is used to "approximate" the render colors?

That's a good idea; we could actually eliminate the entries in the gray 
ramp duplicated within the color cube.

Keith Packard        XFree86 Core Team        HP Cambridge Research Lab


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