Re: [linux-fbdev] Is a FontCache worth implementing ?

[Romain D. <do...@ir...>]

Sven LUTHER wrote:
> On Thu, Mar 08, 2001 at 10:31:12AM +0100, Romain Dolbeau wrote:
> > Yes, that was killed my current (test) implementation : 16 colors
> > mean 16 copies of each glyph. Yuck (8 Mb for 512 glyhs, 16x16 32bpp)
> 
> Are you trully using color glyphs ?

No. I was fbcon_cfb32_putc()'ing in offscreen memory on the first
call, and pm3fb_cfbX_bmove()'ing to put character in place.
but:

1) it doesn't work
2) even if it did, that would eat up half my board memory,
   plus 512bit for the flags (not-yet-written in offscreen)
3) I haven't yet tried to check color, so the current implementation
   would use the color of the first displayed char (OK, it uses less
   memory that way - but it would look ugly, given that I use
   color-ls...)

So I guess that it's not really worth the hassle, there's likely
a better way.

> the glyphs are mostly just a bitmap, you can store them in system or offscreen
> memory, and after that, do a pattern fill using any color you want for
> foreground/background

I have no yet fully understood pattern fill on the pm3

> or even use the Glyph stuff ...

I have no clue how to use it properly

Maybe 3DLabs will answer m  ...(I've tried contacting specific people
that I believe are in the tech dpt. mail didn't bounce...).

> What kind of fonts are in use anyway, mostly they are 8x8 or 8x16 or somethign
> such, isn't it, i think there is also the sunc fonts (22x12 or something
> such).

8x16 seems default, 8x8 works with pm3fb. Don't think Sun22x12 are
supposed
to work on anything but Sun FB (cg3, cg6, ffb & friends)

> I calculated that for small fonts, just sending the font data may require less
> register writes than seting up a blit). This is naturally not true for bigger
> fonts (like 32x32 fonts, but do we use that ?)

Non-scissored _bmove is 4 register writes on pm3, where a 8x16 font
seems to need 8 32 bits memory accesses _per rows_ with cfb32, i.e.
128 memory acesses. And 32 in cfb8. So I'm still looking
for a way to do in-FB memory font rendering...

-- 
DOLBEAU Romain               | l'histoire est entierement vraie, puisque
ENS Cachan / Ker Lann        |     je l'ai imaginee d'un bout a l'autre
do...@ir...             |           -- Boris Vian