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)