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XDGA(3) 										  XDGA(3)

NAME
       XDGA - Client library for the XFree86-DGA extension.

SYNOPSIS
       #include <X11/extensions/xf86dga.h>

       Bool XDGAQueryExtension(
	      Display *dpy,
	      int *eventBase,
	      int *errorBase)

       Bool XDGAQueryVersion(
	      Display *dpy,
	      int *majorVersion,
	      int *minorVersion)

       XDGAMode *XDGAQueryModes(
	      Display *dpy,
	      int screen,
	      int *num)

       XDGADevice *XDGASetMode(
	      Display *dpy,
	      int screen,
	      int mode)

       Bool XDGAOpenFramebuffer(
	      Display *dpy,
	      int screen)

       void XDGACloseFramebuffer(
	      Display *dpy,
	      int screen)

       void XDGASetViewport(
	      Display *dpy,
	      int screen,
	      int x,
	      int y,
	      int flags)

       void XDGAInstallColormap(
	      Display *dpy,
	      int screen,
	      Colormap cmap)

       Colormap XDGACreateColormap(
	      Display *dpy,
	      int screen,
	      XDGADevice *device,
	      int alloc)

       void XDGASelectInput(
	      Display *dpy,
	      int screen,
	      long event_mask)

       void XDGAFillRectangle(
	      Display *dpy,
	      int screen,
	      int x,
	      int y,
	      unsigned int width,
	      unsigned int height,
	      unsigned long color)

       void XDGACopyArea(
	      Display *dpy,
	      int screen,
	      int srcx,
	      int srcy,
	      unsigned int width,
	      unsigned int height,
	      int dstx,
	      int dsty)

       void XDGACopyTransparentArea(
	      Display *dpy,
	      int screen,
	      int srcx,
	      int srcy,
	      unsigned int width,
	      unsigned int height,
	      int dstx,
	      int dsty,
	      unsigned long key)

       int XDGAGetViewportStatus(
	      Display *dpy,
	      int screen)

       void XDGASync(
	      Display *dpy,
	      int screen)

       Bool XDGASetClientVersion(
	      Display *dpy)

       void XDGAChangePixmapMode(
	      Display *dpy,
	      int screen,
	      int *x,
	      int *y,
	      int mode)

       void XDGAKeyEventToXKeyEvent(
	      XDGAKeyEvent *dk,
	      XKeyEvent *xk)

DESCRIPTION
       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  inter-
       face for version 2.0 of the XFree86-DGA extension.

       XFree86-DGA  is not intended as a direct rendering API, but rather, as a mechanism to "get
       the X Server out of the way" so that some other direct rendering API can have full  access
       to  the	hardware.   With this in mind, DGA does provide clients some direct access to the
       hardware without requiring a separate rendering API, but this access is limited to  direct
       linear framebuffer access.

       Most  of  the  reasons  for the XFree86-DGA extension's existence are now better served in
       other ways.  Further development of this extension is not expected, and it may  be  depre-
       cated  in  a  future release.  The features that continue to be useful will either be pro-
       vided through other existing mechanisms, or through an extension that address those  needs
       more specifically.

       XFree86-DGA  is	initialized  by  passing  a  number  corresponding to a valid XDGAMode to
       XDGASetMode().  Clients can get a list of valid modes from  XDGAQueryModes().   Each  XDG-
       AMode corresponds to a different framebuffer layout.

       XDGAQueryModes()  returns a pointer to an array of XDGAModes which are valid for the given
       screen.	num is the number of elements in the array.  The returned array can be freed with
       XFree(3).  The XDGAMode structure is as follows:

       typedef struct {
	  int num;
	  char *name;
	  float verticalRefresh;
	  int flags;
	  int imageWidth;
	  int imageHeight;
	  int pixmapWidth;
	  int pixmapHeight;
	  int bytesPerScanline;
	  int byteOrder;
	  int depth;
	  int bitsPerPixel;
	  unsigned long redMask;
	  unsigned long greenMask;
	  unsigned long blueMask;
	  short visualClass;
	  int viewportWidth;
	  int viewportHeight;
	  int xViewportStep;
	  int yViewportStep;
	  int maxViewportX;
	  int maxViewportY;
	  int viewportFlags;
	  int reserved1;
	  int reserved2;
       } XDGAMode;

       num     A unique identifying number (num > 0) for the mode.  This is the number referenced
	       when initializing the mode.

       name    The name of the corresponding modeline as given in the xorg.conf file.

       verticalRefresh
	       The vertical refresh rate for the modeline (in Hz).

       flags   Any of the following may be OR'd together:

	       XDGAConcurrentAccess
		   Indicates that concurrent client/server access to the framebuffer is possible.
		   If  this  flag  is  not  set  it  is  very important to call XDGASync() before
		   directly accessing the framebuffer if a call to XDGAFillRectangle(), XDGACopy-
		   Area()  or  XDGACopyTransparentArea()  or any Xlib rendering function has been
		   made prior to such accesses.

	       XDGASolidFillRect
		   Indicates that XDGAFillRectangle() is supported.

	       XDGABlitRect
		   Indicates that XDGACopyArea() is supported.

	       XDGABlitTransRect
		   Indicates that XDGACopyTransparentArea() is supported.

	       XDGAPixmap
		   Indicates that a Pixmap will be returned when the mode is  initialized.   This
		   means that rendering with Xlib is possible for this mode.

	       XDGAInterlaced

	       XDGADoublescan
		   Indicates that the mode is an interlaced or doublescan mode.

       imageWidth

       imageHeight
	       The  width and height of the framebuffer area accessible by the client.	This rec-
	       tangle is always justified to the upper left-hand corner.

       pixmapWidth

       pixmapHeight
	       The width and height of the framebuffer area accessible by Xlib.   This	rectangle
	       is always justified to the upper left-hand corner.  These fields are only valid if
	       the XDGAPixmap flag is set in the flags field.

       bytesPerScanline
	       The pitch of the framebuffer in bytes.

       byteOrder
	       MSBFirst or LSBFirst.

       depth   The number of bits in each pixel which contain usable data.

       bitsPerPixel
	       The number of bits taken up by each pixel.

       redMask

       greenMask

       blueMask
	       The RGB masks.  These do not apply to color-indexed modes.

       visualClass
	       TrueColor, PseudoColor, DirectColor, etc.

       viewportWidth

       viewportHeight
	       The dimensions of the portion of the framebuffer which will be  displayed  on  the
	       screen.

       xViewportStep

       yViewportStep
	       The  granularity  of  the  x,y viewport positioning possible with the XDGASetView-
	       port() function.

       maxViewportX

       maxViewportY
	       The maximum x and y positions possible with the XDGASetViewport() function.

       viewportFlags
	       Any of the following may be OR'd together

	       XDGAFlipRetrace
		   Indicates that the hardware can switch viewports during the vertical retrace.

	       XDGAFlipImmediate
		   Indicates that the hardware can switch viewports immediately  without  waiting
		   for the vertical retrace.

       XDGASetMode()  initialises the XDGAMode corresponding to num.  To exit DGA mode and return
       to normal server operation, call  XDGASetMode()	with  num  set	to  zero.   XDGASetMode()
       returns	a  pointer  to	an  XDGADevice	if  successful.  The XDGADevice can be freed with
       XFree(3).  The XDGADevice structure is as follows:

       typedef struct {
	  XDGAMode mode;
	  unsigned char *data;
	  Pixmap pixmap;
       } XDGADevice;

       mode    The XDGAMode structure, identical to the information returned by XDGAQueryModes().

       data    If direct framebuffer access is desired and possible, this field  will  contain	a
	       pointer	to  the  mapped  framebuffer  memory.  Generally, this field will be zero
	       unless a call to XDGAOpenFramebuffer() is made  prior  to  initialization  of  the
	       mode.

       pixmap  If the mode supports Xlib rendering as indicated by XDGAPixmap in the flags field,
	       this will contain a Pixmap handle suitable for passing as the drawable argument to
	       Xlib functions.	This field will be zero if Xlib rendering is not supported.

       XDGAQueryExtension()  checks  for  the presence of the extension and returns the event and
       error bases.

       XDGAQueryVersion() returns the XFree86-DGA major and minor version numbers.

       XDGAOpenFramebuffer() maps the framebuffer memory.  The client needs sufficient privileges
       to be able to do this.  XDGAOpenFramebuffer() should be called prior to initializing a DGA
       mode if direct framebuffer access is desired for that  mode.   XDGAOpenFramebuffer()  does
       not need to be called if direct framebuffer access is not required.  If the framebuffer is
       opened,

       XDGACloseFramebuffer() should be called prior to client exit to unmap the memory.

       XDGAChangePixmapMode() can be used to change between two pixmap sizes  in  cases  where	a
       Pixmap  is  available for Xlib rendering.  The following values for the mode parameter are
       available:

	       XDGAPixmapModeLarge
		   The pixmap size is defined by the pixmapWidth and pixmapHeight fields  in  the
		   XDGAMode structure.	The x and y values are ignored in this case.

	       XDGAPixmapModeSmall
		   The	pixmap	size is defined by the viewportWidth and viewportHeight fields in
		   the XDGAMode structure.  In this mode, the x and y values specify where in the
		   framebuffer	this  pixmap  rectangle  is  located.	It may be placed anywhere
		   within  the	Xlib  renderable  region  described  by   the	pixmapWidth   and
		   pixmapHeight  fields  in  the  XDGAMode.   The x and y values returned are the
		   resultant location of the pixmap and may be different from the  requested  x,y
		   location  due  to platform specific alignment constraints.  All Xlib rendering
		   is clipped to this pixmap rectangle.

       XDGASetViewport() sets the upper left-hand corner of the rectangle of framebuffer that  is
       to  be  displayed  on  the screen.  Not all locations may be supported by the hardware and
       requested locations will be adjusted according  to  the	xViewportStep  and  yViewportStep
       fields in the XDGAMode.

       flags  can  be XDGAFlipRetrace or XDGAFlipImmediate to adjust the viewport location at the
       next vertical retrace or immediately.  Values other than the supported  values  advertised
       in  the	mode's	viewportFlags  field  will  result in hardware-specific default behavior.
       XDGAFlipImmediate will block until the flip is completed.  XDGAFlipRetrace will	generally
       NOT  block so it is necessary to monitor the viewport status with XDGAGetViewportStatus().
       XDGAFlipImmediate requests during pending XDGAFlipRetrace requests will be ignored.

       XDGAGetViewportStatus() keeps track of the XDGASetViewport() requests still pending.   The
       return value of the function will have consecutive bits set (LSB justified), each bit rep-
       resenting a pending viewport change.  For example:

	    while(XDGAGetViewportStatus(dpy, screen));

       waits for all pending viewport changes to finish.

	    while(0x2 & XDGAGetViewportStatus(dpy, screen));

       waits until all but the last viewport changes have completed.

       XDGACreateColormap() is similar to the Xlib function  XCreateColormap(3)  except  that  it
       takes  an  XDGADevice  as  an argument instead of a Window and Visual.  Though XCreateCol-
       ormap(3) may create usable colormaps in some cases, XDGACreateColormap() is the	preferred
       method  for creating colormaps in DGA since there may not be an advertised visual compati-
       ble with the DGA device.

       XDGAInstallColormap() must be used to install colormaps in DGA mode.   XInstallColormap(3)
       will not work.

       XDGASelectInput() enables DGA's own event mechanism.  This function is similar to XSelect-
       Input(3), and all Xlib Key, Button and Motion masks  are  supported.   The  following  DGA
       events are defined:

       typedef struct {
	  int type;		/* ButtonPress or ButtonRelease + the DGA event base*/
	  unsigned long serial; /* # or last request processed by the server */
	  Display *display;	/* Display the event was read from */
	  int screen;		/* The screen number the event came from */
	  Time time;		/* milliseconds */
	  unsigned int state;	/* key or button mask */
	  unsigned int button;	/* detail */
       } XDGAButtonEvent;

       typedef struct {
	  int type;		/* KeyPress or KeyRelease + the DGA event base*/
	  unsigned long serial; /* # or last request processed by the server */
	  Display *display;	/* Display the event was read from */
	  int screen;		/* The screen number the event came from */
	  Time time;		/* milliseconds */
	  unsigned int state;	/* key or button mask */
	  unsigned int keycode; /* detail */
       } XDGAKeyEvent;

       typedef struct {
	  int type;		/* MotionNotify + the DGA event base*/
	  unsigned long serial; /* # or last request processed by the server */
	  Display *display;	/* Display the event was read from */
	  int screen;		/* The screen number the event came from */
	  Time time;		/* milliseconds */
	  unsigned int state;	/* key or button mask */
	  int dx;		/* relative pointer motion */
	  int dy;		/* relative pointer motion */
       } XDGAMotionEvent;

       XDGAKeyEventToXKeyEvent()  is a helper function to translate XDGAKeyEvents into XKeyEvents
       suitable for use with XLookupKeysym(3).

       XDGAFillRectangle(), XDGACopyArea(), and XDGACopyTransparentArea() are included with  some
       reservation  since  DGA	is not intended as a rendering API.  These are merely convenience
       routines and are optionally supported.  The associated flags will be set in the XDGAMode's
       flags  field  if these functions are supported.	These functions will be no-ops otherwise.
       they do not provide direct access to the hardware, but are simply context-less  operations
       performed by the server.

       XDGASync() blocks until all server rendering to the framebuffer completes.  If Xlib or the
       3 rendering functions above are used, XDGASync() must be called before the client directly
       accesses  the  framebuffer as the server rendering is asynchronous with the client and may
       have not completed.  This is especially important if the XDGAConcurrentAccess flag is  not
       set  in	the  XDGAMode's  flags field since concurrent access by the server and client may
       result in a system lockup.

SEE ALSO
       Xorg(1), xorg.conf(5)

AUTHORS
       XFree86-DGA version 2 was written by Mark Vojkovich.  Version 1 was written by Jon  Tombs,
       Harm Hanemaayer, Mark Vojkovich.

X Version 11				libXxf86dga 1.1.4				  XDGA(3)
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