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.