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 interface 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 deprecated in a future release. The
features that continue to be useful will either be provided 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 XDGAMode 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(),
XDGACopyArea() 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 rectangle 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 XDGASetViewport() 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 representing 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 XCreateColormap(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 compatible
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 XSelectInput(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.