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<H1>XShm</H1>
Section: X FUNCTIONS (3)<BR>Updated: libXext 1.3.4<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
XShmQueryExtension, XShmQueryVersion, XShmPixmapFormat, XShmAttach, XShmDetach
XShmCreateImage, XShmPutImage, XShmGetImage, XShmCreatePixmap, XShmGetEventBase - X Shared Memory extension functions
<A NAME="lbAC">&nbsp;</A>
<H2>SYNTAX</H2>
<PRE>
#include &lt;<A HREF="file:///usr/include/X11/Xlib.h">X11/Xlib.h</A>&gt;
#include &lt;<A HREF="file:///usr/include/sys/ipc.h">sys/ipc.h</A>&gt;
#include &lt;<A HREF="file:///usr/include/sys/shm.h">sys/shm.h</A>&gt;
#include &lt;<A HREF="file:///usr/include/X11/extensions/XShm.h">X11/extensions/XShm.h</A>&gt;
Bool XShmQueryExtension(
Display *display);
Bool XShmQueryVersion(
Display *display;
int *major, *minor;
Bool *pixmaps);
int XShmPixmapFormat(
Display *display);
Bool XShmAttach(
Display *display;
XShmSegmentInfo *shminfo);
Bool XShmDetach(
Display *display;
XShmSegmentInfo *shminfo);
XImage *XShmCreateImage (
Display *display;
Visual *visual;
unsigned int depth;
int format;
char *data;
XShmSegmentInfo *shminfo;
unsigned int width, height);
Bool XShmPutImage(
Display *display;
Drawable d;
GC gc;
XImage *image;
int src_x, src_y, dest_x, dest_y;
unsigned int width, height;
bool send_event);
Bool XShmGetImage (
Display *display;
Drawable d;
XImage *image;
int x, y;
unsigned long plane_mask);
Pixmap XShmCreatePixmap(
Display *display;
Drawable d;
char *data;
XShmSegmentInfo *shminfo;
unsigned int width, height, depth);
Status XShmGetEventBase(
Display *display);
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>STRUCTURES</H2>
<PRE>
<I>Events:</I>
typedef struct {
int type; /* of event */
unsigned long serial; /* # of last request processed by server*/
Bool send_event; /* true if this came from a SendEvent request*/
Display *display; /* Display the event was read from */
Drawable drawable; /* drawable of request */
int major_code; /* ShmReqCode */
int minor_code; /* X_ShmPutImage */
ShmSeg shmseg; /* the ShmSeg used in the request*/
unsigned long offset; /* the offset into ShmSeg used in the request*/
} XShmCompletionEvent;
<I>a structure of type XShmSegmentInfo :</I>
typedef struct {
ShmSeg shmseg; /* resource id */
int shmid; /* kernel id */
char *shmaddr; /* address in client */
Bool readOnly; /* how the server should attach it */
} XShmSegmentInfo;
</PRE><A NAME="lbAE">&nbsp;</A>
<H2>DESCRIPTION</H2>
<P>
<P>
<I>XShmQueryExtension</I>
checks to see if the shared memory extensions are available for the
specified display.
<P>
<I>XShmQueryVersion</I>
returns the version numbers of the extension implementation. Shared
memory pixmaps are supported if the pixmaps argument returns true.
<P>
<I>XShmAttach</I>
tells the server to attach to your shared memory segment. If all goes
well, you will get a non-zero status, back and your XImage is ready
for use.
<P>
<I>XShmDetach</I>
tells the server to detach from your shared memory segment.
<P>
<I>XShmPutImage</I>
combines an image in memory with a shape of the specified drawable. If
XYBitmap format is used, the depth must be one, or a ``BadMatch''
error results. The foreground pixel in the GC defines the source for
the one bits in the image, and the background pixel defines the source
for the zero bits. For XYPixmap and ZPixmap, the depth must match the
depth of the drawable, or a ``BadMatch'' error results.
<P>
<I>XShmGetImage</I>
reads image data into a shared memory XImage where display is the
display of interest, drawable is the source drawable, image is the
destination XImage, x and y are offsets within the drawable, and
plane_mask defines which planes are to be read.
<P>
<I>XShmCreateImage</I>
allocates the memory needed for an XImage structure for the specified
display but does not allocate space for the image itself.
<P>
<I>XShmPixmapFormat</I>
gets the format for the server. If your application can deal with the
server pixmap data format, a shared memory segment and shminfo
structure are created.
<P>
<I>XShmCreatePixmap</I>
points to a pixmap which you can manipulate in all of the usual ways,
with the added bonus of being able to edit its contents directly
through the shared memory segment.
<P>
<I>XShmGetEventBase</I>
gets the completion event value.
<P>
<A NAME="lbAF">&nbsp;</A>
<H2>SEE ALSO</H2>
<I>MIT-SHM - The MIT Shared Memory Extension </I>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="1"><A HREF="#lbAB">NAME</A><DD>
<DT id="2"><A HREF="#lbAC">SYNTAX</A><DD>
<DT id="3"><A HREF="#lbAD">STRUCTURES</A><DD>
<DT id="4"><A HREF="#lbAE">DESCRIPTION</A><DD>
<DT id="5"><A HREF="#lbAF">SEE ALSO</A><DD>
</DL>
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