NAME

       X11::Protocol::Ext::XFree86_DGA - direct video memory access

SYNOPSIS

        use X11::Protocol;
        my $X = X11::Protocol->new;
        $X->init_extension('XFree86-DGA')
          or print "XFree86-DGA extension not available";

DESCRIPTION

       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 physical 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.)

REQUESTS

       The following requests are made available with an "init_extension()", as per "EXTENSIONS"
       in X11::Protocol.

           my $ext_available = $X->init_extension('XFree86-DGA');

   XFree86-DGA 1.0
       "($server_major, $server_minor) = $X->XF86DGAQueryVersion()"
           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 "XF86DGANoDirectVideoMode".

       "($address, $width, $bank_size_bytes, $ram_size_kbytes) = $X->XF86DGAGetVideoLL
       ($screen_num)"
           Return the location and size of the video memory for $screen_num (integer 0 upwards).

           $address is a raw physical 32-bit address as an integer.  $width is in pixels.

           $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 "XF86DGAScreenNotActive".

       "($width, $height) = $X->XF86DGAGetViewPortSize ($screen_num)"
           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, $colormap)"
           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 "XF86DGAScreenNotActive" or "XF86DGADirectNotActivated" results.

       "$bool = $X->XF86DGAViewPortChanged ($screen_num, $num_pages)"
           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.

SEE ALSO

       X11::Protocol

       /usr/share/doc/xserver-xfree86/README.DGA.gz

HOME PAGE

       <http://user42.tuxfamily.org/x11-protocol-other/index.html>

LICENSE

       Copyright 2011, 2012, 2013, 2014, 2017 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 details.

       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/>.