DirectColor visuals

[Francisco Rojas <rojas at hyperion dot ece dot arizona dot edu>]

Thanks for taking time to address my issue.

>Francisco,

>Do you know what a DirectColor visual is?
 I believe so.  Officially, direct color is the superset for
colormaps excluding TrueColor. Unofficially, it allows for simultaneous
usage of several colormaps, normally Xservers allow (3 simultanous
colormaps-read/write (dynamic) based on Xlib books).

>Do you know why you would need a DirectColor visual?
 We have a pseudo-color application in-which we update the bitmaps
using the colormap table, which are updated through mouse events. The
bitmaps are typically on the order of 1024x1024.
(Without the read/write colormaps we would have to
redraw the pixmaps everytime, too much to update. I have tried this
using TrueColor already. We can get redraw update delays on the order of
several seconds and get performance issues with X)

The problem with this program is the flickering in 8 bit mode. Most of the
window managers want to use a wide range of colors (openbox, afterstep,
etc..). To minimize the flickering, we attempt to take over the screen
and switch the Xserver and window manager to 8 bits. (We still get
flickering)

Ideally, I would like do be able to allocate a dynamic colormap without
all the flickering associated in 8 bit by running in 24 bit, thus
directcolor, and be able to do the same updates without redrawing the
pixmaps as we currently do.

Actually, I would be satisfied, if the XFree86 running 24 bit True color
would have a 8 bit pseudocolor visual available and be reported by
xdpyinfo. Then I could match the visual and be happy..:)

--I am not sure how to enable backingstore with cygwin/XFree86 either.


>Do you know of any Windows-based graphics cards that actually support
>DirectColor?

--Actually, I do not know. I have only seen DirectColor visuals reported
on some of the emails on the internet by searching "directcolor xfree86"


>My understanding of DirectColor is that it allows you to specify the
range of colors that will be used in a mode that is similar to TrueColor...
>however, I don't know of a single Windows graphics card that allows you
to do that. I don't know of any program that utilizes such a visual either.
>As such, there is no support for DirectColor in Cygwin/XFree86. I don't
>expect that there will ever be DirectColor support in Cygwin/XFree86
>unless someone can explain to me that I am way wrong.

>DirectColor seems like a lot of things in X: it was thought to be REALLY
>useful when X was designed, but it turned out to be anything but useful.
>I read about those things once, then I ignore them after that.
>So, anyone else know what DirectColor is?
>Harold

So inconclusion, DirectColor is not available to cygwin/XFree86 ?

Are there cases where I can run TrueColor and have a pseudocolor visual
available with/or without a different graphics card. I'll buy one ?


Thanks again for your time.


Francisco Rojas
Electrical and Computer Engineering Department
University of Arizona, Tucson, Arizona
OFFICE: ECE 408, 520.621.4554
FAX   :          520.621.8076
----

On Mon, 13 Jan 2003, Francisco Rojas wrote:

>
> I am running the lastest cygwin and xfree86.
> In 24 bit mode, I only get the TrueColor Visual.
> What I do I need to do to get a DirectColor Visual
>  listed using xdpyinfo ?
>
> Currently, I am running a NVIDIA Gforce2 400?
> If I need to change videocards what are the recommended cards?
> I have not seen anything in the documentation or mailing lists.
>
>
>
>
> $ xdpyinfo
> name of display:    :0.0
> version number:    11.0
> vendor string:    The XFree86 Project, Inc
> vendor release number:    40200000
> XFree86 version: 4.2.0
> maximum request size:  4194300 bytes
> motion buffer size:  256
> bitmap unit, bit order, padding:    32, LSBFirst, 32
> image byte order:    LSBFirst
> number of supported pixmap formats:    7
> supported pixmap formats:
>     depth 1, bits_per_pixel 1, scanline_pad 32
>     depth 4, bits_per_pixel 8, scanline_pad 32
>     depth 8, bits_per_pixel 8, scanline_pad 32
>     depth 15, bits_per_pixel 16, scanline_pad 32
>     depth 16, bits_per_pixel 16, scanline_pad 32
>     depth 24, bits_per_pixel 32, scanline_pad 32
>     depth 32, bits_per_pixel 32, scanline_pad 32
> keycode range:    minimum 8, maximum 255
> focus:  window 0x400002, revert to PointerRoot
> number of extensions:    21
>     BIG-REQUESTS
>     DEC-XTRAP
>     DOUBLE-BUFFER
>     Extended-Visual-Information
>     FontCache
>     GLX
>     LBX
>     MIT-SUNDRY-NONSTANDARD
>     RECORD
>     RENDER
>     SECURITY
>     SGI-GLX
>     SHAPE
>     SYNC
>     TOG-CUP
>     XC-APPGROUP
>     XC-MISC
>     XFree86-Bigfont
>     XKEYBOARD
>     XTEST
>     XVideo
> default screen number:    0
> number of screens:    1
>
>
> screen #0:
>   dimensions:    1274x961 pixels (431x325 millimeters)
>   resolution:    75x75 dots per inch
>   depths (7):    24, 1, 4, 8, 15, 16, 32
>   root window id:    0x36
>   depth of root window:    24 planes
>   number of colormaps:    minimum 1, maximum 1
>   default colormap:    0x20
>   default number of colormap cells:    256
>   preallocated pixels:    black 0, white 16777215
>   options:    backing-store NO, save-unders NO
>   largest cursor:    1274x961
>   current input event mask:    0xd0001f
>     KeyPressMask             KeyReleaseMask           ButtonPressMask
>     ButtonReleaseMask        EnterWindowMask
> SubstructureRedirectMask
>     PropertyChangeMask       ColormapChangeMask
>   number of visuals:    2
>   default visual id:  0x22
>   visual:
>     visual id:    0x22
>     class:    TrueColor
>     depth:    24 planes
>     available colormap entries:    256 per subfield
>     red, green, blue masks:    0xff0000, 0xff00, 0xff
>     significant bits in color specification:    8 bits
>   visual:
>     visual id:    0x23
>     class:    TrueColor
>     depth:    24 planes
>     available colormap entries:    256 per subfield
>     red, green, blue masks:    0xff0000, 0xff00, 0xff
>     significant bits in color specification:    8 bits
>
>
>
> Francisco Rojas
> Electrical and Computer Engineering Department
> University of Arizona, Tucson, Arizona
> OFFICE: ECE 408, 520.621.4554
> FAX   :          520.621.8076
> ----
>
>