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

[Sven L. <lu...@dp...>]

On Thu, Mar 08, 2001 at 04:56:01PM +0100, Romain Dolbeau wrote:
> 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

mostly you do expand a bitmap so that all 1s become the foreground color and
all 0s are either transparent or background color. look at writebitmap and
cpu2screencolor expansion code in the glint driver. I cannot say more about
it.

> > or even use the Glyph stuff ...
> 
> I have no clue how to use it properly

Same here ...

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

mmm, i hope you luck on this.

> > 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)

Well, yes they work nicely on high resolution fbdevs, try reading 8x8 fonts on
resolutions above 1024x768 on a 15" monitor ...

> > 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...

glyph should bring that donw to 4 32 bit register writes, and 2 for 8x8 fonts.

Friendly,

Sven Luther