X11::Protocol::Ext::XFree86_DGA - direct video memory access
my $X = X11::Protocol->new;
or print "XFree86-DGA extension not available";
The XFree86-DGA extension provides direct access to the video RAM of the server
display. A client program running on the same machine can use this to read or
write directly instead of going through the X protocol.
Accessing video memory will require some system-dependent trickery. Under the
Linux kernel for example video RAM is part of the /dev/mem
address space and can be brought into program address space with an
"mmap()" or accessed with "sysread()" and
"syswrite()". This normally requires root permissions.
The requests offered here are only XFree86-DGA version 1.0 as yet and they don't
say anything about the pixel layout etc in the memory -- that has to be
divined separately. (Version 2.0 has more for that.)
The following requests are made available with an "init_extension()",
as per "EXTENSIONS" in X11::Protocol.
my $ext_available = $X->init_extension('XFree86-DGA');
- "($server_major, $server_minor) =
- Return the DGA protocol version implemented by the server.
- "$flags = $X->XF86DGAQueryDirectVideo ($screen_num)"
- Get flags describing direct video access on $screen_num (integer 0
upwards). The only flag bit is
0x0001 direct video available
It's possible to have the extension available but no direct video on a
particular screen, or even on no screens at all. When no direct video the
requests below give protocol error
- "($address, $width, $bank_size_bytes, $ram_size_kbytes) =
- Return the location and size of the video memory for $screen_num (integer
$address is a raw physical 32-bit address as an integer. $width is in
$bank_size_bytes is the size in bytes accessible at a given time.
$ram_size_kbytes is the total memory in 1024 byte blocks. If
"$ram_size_kbytes*1024" is bigger than $bank_size_bytes then
"$X->XF86DGASetVidPage()" below must be used to switch among
the banks to access all the RAM.
- "$X->XF86DGADirectVideo ($screen_num, $flags)"
- Enable or disable direct video access on $screen_num (integer 0 upwards).
$flags is bits
0x0002 enable direct video graphics
0x0004 enable mouse pointer reporting as relative
0x0008 enable direct keyboard event reporting
When direct video graphics is enabled (bit 0x0002) the server gives up
control to the client program.
If the graphics card doesn't have a direct video mode then an
"XF86DGANoDirectVideoMode" error results, or if the screen is
not active (eg. switched away to a different virtual terminal) then
- "($width, $height) = $X->XF86DGAGetViewPortSize
- Get the size of the viewport on $screen_num (integer 0 upwards). This is
the part of the video memory actually visible on the monitor. The memory
might be bigger than the monitor.
- "$X->XF86DGASetViewPort ($screen_num, $x, $y)"
- Set the coordinates of the top-left corner of the visible part of the
video memory on $screen_num (integer 0 upwards).
This can be used when the video memory is bigger than the monitor to pan
around that bigger area. It can also be used for some double-buffering to
display one part of memory while drawing to another.
- "$vidpage = $X->XF86DGAGetVidPage ($screen_num)"
- "$X->XF86DGASetVidPage ($screen_num, $vidpage)"
- Get or set the video page (bank) on $screen_num (integer 0 upwards).
$vidpage is an integer 0 upwards.
This is used to access all the RAM when when the bank size is less than the
total memory size (per "XF86DGAGetVideoLL()" above).
- "$vidpage = $X->XF86DGAInstallColormap ($screen_num,
- Set the colormap on $screen_num to $colormap (integer XID).
This can only be used while direct video is enabled (per
"XF86DGADirectVideo()" above) or an error
- "$bool = $X->XF86DGAViewPortChanged ($screen_num,
- Check whether a previous "XF86DGASetViewPort()" on $screen_num
(integer 0 upwards) has completed, meaning a vertical retrace has occurred
since that viewport location was set.
This is used for double-buffering (or N-multi-buffering) to check a viewport
change has become visible. $num_pages should be 2 for double-buffering and
can be higher for multi-buffering.
Copyright 2011, 2012, 2013, 2014 Kevin Ryde
X11-Protocol-Other is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later version.
X11-Protocol-Other is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
You should have received a copy of the GNU General Public License along with
X11-Protocol-Other. If not, see <http://www.gnu.org/licenses/>.