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

[James S. <jsi...@li...>]

>Well, but mostly the expensive part of it is passing from the system
>memory to the card memory, where the bus is limiting us.

I know. That is why I'm pushing this fbcon to accel-con move.

>but you could use this 64 glyphs as a cache, or something such, uploading
>only the most used chars or something such.
>
>That said, other cards can use standard FB memory for font cache, and
>then either do a blit or a pattern expansion to the screen.

True. You could do this for cards that have the avaliable memory. If fbcon
is running at a resolution that occupies the entire memory then you are in
trouble. You can do many fancy tricks. I leave it up to the driver writer
to be fancy. The goal is to draw some image. Keep in mind I wanted to also
want to have the function draw the penguin. It is very miss leading the
name of the function. It should be drawimage instead. Also for cards that
lack this function a software emulated drawimage has to be done. Could
people post all the possible ways a "fontcache" could work. I see
imagedraw is going to the touchy one.

>What about pattern fills ? Where you provide a bitmap, and the accel
>engine copies this bitmap, putting 1 color for the 1s and another (or
>transparent) for 0s.

Same thing. The goal of the function is to draw some image. How it is
implemented is up to the driver. Another way to do it is make textures of
fonts and using texture mapping to draw the characters. I seen something
like this used for a X server before. The windowing was done with the z
buffer which was used to act like hardware window IDs. Each window then
was textured mapped with whatever the program was trying to display. The
texture map changed when needed. X term wa steh trickiest. Alot of little
texture maps but it still was fast.

MS: (n) 1. A debilitating and surprisingly widespread affliction that
renders the sufferer barely able to perform the simplest task. 2. A disease.

James Simmons  [jsi...@li...]               ____/|
fbdev/console/gfx developer                             \ o.O|
http://www.linux-fbdev.org                               =(_)=
http://linuxgfx.sourceforge.net                            U
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