nanogui: NanoGUI palette model
Subject:
RE: NanoGUI palette model
From:
Greg Haerr ####@####.####
Date:
29 Sep 1999 17:09:35 -0000
Message-Id: <01BF0A6A.803FF6F0.greg@censoft.com>
: >Please, add also 4bpp directcolor (16 level gray scale) into the soup. I have
: >such a hardware (320x240 lcd) and I'm dreaming on using linux and NanoGUI
: >with
: >it. Linux frame buffer is working already.
:
: That can easily be handled. The palette code in Microwindows doesn't attempt
: to set any hardware palette, but just maps the palette the driver presents
: to any palette user attempts to set. In this case the hardware driver thus
: will only present a 16 level gray scale palette.
:
That's not true. MicroWindows does set hw palettes, thru the setpalette
screen driver entry point. Basically, MicroWindows is linked with one of the devpalX.c
files, which are pre-built palettes for 2, 8, 16 or 256 colors. The first thing
that happens is the MicroWindows sets the hardware palette for the first X entries
from this table. The driver is responsible for converting RGB entries to PIXELVALs.
Normally, this is extremely simple, as the palette index is the PIXELVAL and the
contents are the COLORVAL.
During operation, MicroWindows may "extend" the palette beyond the initial
range for display of large color images. In this case, MicroWindows calls the device
driver setpalette function again.
Microwindows always calls the setpalette function, there is no need for a
getpalette function, instead, the initial devpalX.c handles this.
Greg
