NAME¶
DMXGetWindowAttributes - determine back-end window attributes
SYNOPSIS¶
#include <X11/extensions/dmxext.h>
Bool DMXGetWindowAttributes(Display *dpy,
Window window,
int *screen_count,
int available_count,
DMXWindowAttributes *attr);
DESCRIPTION¶
When calling
DMXGetWindowAttributes(),
window specifies the window
ID of a window on the
Xdmx(1) server and
available_count
specifies the length of
attr.
The number of screens for which information is available will be returned in
screen_count and information about those screen will be returned in
attr. If
screen_count is less than
available_count, then
information for all of the screens will be returned. Otherwise, information
for the first
available_count screens will be returned.
The
DMXWindowAttributes structure is:
typedef struct {
int screen;
Window window;
XRectangle pos, vis;
} DMXWindowAttributes;
For each back-end X server that displays a portion of
window, this
structure contains the physical
screen containing that portion, the
window ID on the back-end X server of the window containing that
portion, the position and dimensions of the window on the back-end
(
pos, in screen coordinates), and the visible area of the window on the
back-end (
vis, in window-relative coordinates -- all zeros if the
window is not visible on the backend).
To obtain more information about the physical screen use the
DMXGetScreenAttributes(3) call.
Note that DMX allows multiple back-end windows to overlap in their view of the
DMX logical window. Further, a logical window does not have to be completely
covered by back-end windows -- there may be gaps.
As an example, consider a 500x500 window that spans the top two 1024x768
back-end displays (A and B) of a 2048x1536 DMX display composed of 4 1024x768
back-end displays arranged in a cube:
A B
C D
In this case, the DMXGetWindowAttributes call would return the following
information for the 500x500 window:
display A: 500x500 window at 1024-250,0 (relative to back end)
with 250x500 visible at 0,0 (relative to window origin)
display B: 500x500 window at -250,0 (relative to back end)
with 250x500 visible at 250,0 (relative to window origin)
display C: 500x500 window at 1024-250,-768 with 0x0 visible at 0,0
display D: 500x500 window at -250,-768 with 0x0 visible at 0,0
RETURN VALUE¶
DMXGetWindowAttributes() returns
True unless there is a protocol
error.
DMXGetWindowAttributes() can generate
BadWindow and
BadAlloc errors.
NOTES¶
Because this call transports a great deal of information over the wire, please
call
DMXGetScreenCount(3) first, and make sure
attr is
sufficiently large.
On a particular back-end server, it is possible that the associated window has
not yet been mapped because the
XMapWindow(3) call that will eventually
map the window had been buffered by Xlib's normal buffering system. To avoid
this race condition, please call
DMXSync(3) before communicating
directly with the back-end X server.
SEE ALSO¶
DMXGetScreenCount(3),
DMXSync(3),
DMXGetScreenAttributes(3),
DMX(3),
Xdmx(1)