
                           XFree86-DGA Extension

The XFree86-DGA extension is an X server extension for allowing client
programs direct access to the video frame buffer.

This is a brief description of the programming interface for the
XFree86-DGA extension.  This describes version 1.0, which is the first
official version.  The interface should remain compatible in future
versions.  The functions described here are found in the library
libXxf86dga.a.

Prototypes for these functions can be found in <X11/extensions/xf86dga.h>

  XF86DGAQueryVersion(Display *display, int *majorVersion, int *minorVersion)

     query the XFree86-DGA version


  XF86DGAQueryExtension(Display *display, int *eventBase, int *errorBase)

     returns the eventBase and errorBase for the XFree86-DGA extension


  XF86DGAQueryDirectVideo(Display *display, int screen, int *flags)

     Query the DirectVideo capabilities of the graphics device. Flags
     are returned, which may be interpreted as follows (bit masks):

       XF86DGADirectPresent          DirectVideo support is present


  XF86DGAGetVideo(Display *display, int screen, char **addr, int *width,
                  int *bankSize, int *memSize);

     returns a pointer to the start of the video framebuffer (*addr),
     the line width (*width), memory bank size (*bankSize) and total
     memory size (*memSize).  Mapping the video framebuffer is a
     privileged operation on most OSs (usually mmap of /dev/mem),
     so a program using this must usually be setuid (or perhaps setgid)
     at least up until the point the function is called.


  XF86DGAGetViewPortSize(Display *display, int screen, int *width,
                         int *height)

     Returns the width (*width) and height (*height) of the view port,
     which is the part of the framebuffer that is visible on the monitor.


  XF86DGADirectVideo(Display *display, int screen, int flags)

     enables/disables Direct Video mode.  When Direct Video mode is
     enabled, the X server gives up control of the framebuffer to the
     client.  When flags is zero, Direct Video mode is disabled.  flags
     may be a bit-wise combination of the following:

       XF86DGADirectGraphics          enable Direct Video mode
       XF86DGADirectMouse             enable reporting of pointer movement
                                      as relative motion
       XF86DGADirectKeyb              enable direct reporting of keyboard
                                      events


  XF86DGASetVidPage(Display *display, int screen, int page)

     Set the framebuffer page.  This is only required for hardware which
     has a banked memory layout (ie, bankSize < memSize).


  XF86DGASetViewPort(Display *display, int screen, int x, int y)

     Set the coordinates of the upper-left corner of the view port to (x,y).


  Bool XF86DGAViewPortChanged(Display *display, int screen, int n)

     Checks whether a previous SetViewPort command has been performed
     by the hardware, that is, whether a vertical retrace has occurred
     since a previous SetViewPort. This can (must, in fact) be used
     with page-flipping; you can start writing to the next page only when
     this function returns TRUE. For some devices this will be the
     case immediately after SetViewPort, however this may be changed in
     in the future. The number of pages used is specified with n; it
     should be 2 for simple page flipping. If n is greater than two
     (triple or multi-buffering), the function checks whether the
     (n - 2)-before-last SetViewPort has been performed.


  XF86DGAInstallColormap(Display *display, int screen, Colormap cmap)

     Set the current colormap of the display to cmap. XF86DGADirectGraphics
     must be active on the display/screen before calling
     XF86DGAInstallColormap or it will produce the error XF86DGAScreenNotActive
     or XF86DGADirectNotActivated.


  int XF86DGAForkApp(int screen)

     Fork the app, parent process hangs around to return non DGA mode should
     the child exit for any reason. Returns 0, or error returned by fork().

$XFree86: xc/programs/Xserver/hw/xfree86/doc/README.DGA,v 3.4 1996/10/17 15:18:47 dawes Exp $
