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

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

On Thu, Mar 08, 2001 at 10:31:12AM +0100, Romain Dolbeau wrote:
> James Simmons wrote:
> 
> > If you think about it we already have something like that with teh current
> > system execpt instead of it being in card memory it is in system memory.
> 
> The idea was to avoid going over the bus : PCI is slow (in particular
> the sh*tty implementation in my PM7500)
> 
> > Using a image blitter you can translate that data from normal RAM to the
> > video card memory. The nice thing about a image blitter is you can do
> > depth translations (mono to depth X).
> 
> 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 ?

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, or even use the Glyph stuff ...

> > I though about using a Glyhp
> > approach. The voodoo 3 card has a pattern buffer for up to 64 Glyphs which
> > can then be very quickly painted on the display. The problem is the
> > console system supports alot more characters than that. In the future I
> > hope even more.
> 
> There's some "glyph" stuff in the pm3, unfortunately, I can only
> get nice little rectangle ATM. Not very useful. I haven't managed
> to get it to use the glyph data I (try to) send :-(

:)))


> If only 3DLabs would distribute the doc :-(

:(((

> > Yes. This is the way the ruby tree handles it. I just got it working in
> > the ruby tree. The only problem is their is some bug in take_over_console
> > I have to chase down but I do have fbcon running using a voodoo 3 along
> > side my MDA. There are 3 functions. One is rectfill which does things like
> > clear the margins etc.
> 
> That's a more generalized _clear + _clear_margins ?
> 
> > Then their is fb_copyarea which copys a area of the
> > screen to another area of the screen.
> 
> better _bmove ? (if only I could get _that_ one to work
> reliably)
> 
> > The last function is fb_imageblit
> > which transfers data from host memory to screen memory.
> 
> Thats seems new to me (I only know 2.2 and 2.4, as I only grep'ped
> through Ruby). Could be useful...
> 
> > This is used to
> > draw the penguin and text. Yes it is simpler to use the accel engine. A
> > good example is the new tdfx driver in the ruby CVS.
> 
> The idea was to avoid the bus ; maybe I'm biased (or totally wrong),
> but the less things go over the bus, the better I feel...

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).

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 ?)

Friendly,

Sven Luther