GLXGETTRANSPARENTINDEXSUN(3glx)GLXGETTRANSPARENTINDEXSUN(3glx)NAMEglXGetTransparentIndexSUN - get the transparent pixel index for an
overlay/underlay Window pair.
C SPECIFICATION
Status glXGetTransparentIndexSUN( Display *dpy,
Window overlay,
Window underlay,
unsigned int *pTransparentIndex )
PARAMETERS
dpy Specifies the connection to the X server
overlay
Specifies the overlay Window of an overlay/underlay pair.
underlay
Specifies the underlay Window.
pTransparentIndex
Specifies a pointer to the index to be returned.
RETURN
If underlay is a Window that has previously been made the current GLX‐
Drawable by the client, and a transparent index is available for the
overlay Window,
glXGetTransparentIndexSUN returns 1 and sets *pTransparentIndex to the
value of the index. Otherwise, it returns 0.
If underlay is equal to None, and if a transparent index is available
for overlay that is independent of the underlying Windows, glXGetTrans‐
parentIndexSUN returns 1 and sets *pTransparentIndex to the index. Oth‐
erwise, it returns 0.
DESCRIPTION
For some overlay Windows (windows created with a visual with GLX_LEVEL
> 0), there is a particular color index that when drawn to the frame‐
buffer causes pixels in the Window to be transparent. That is, pixels
in the overlay drawn with the transparent index are invisible and the
pixels of window(s) beneath the overlay are displayed.
On some systems, the transparent pixel index is a constant. On other
hardware, the transparent index is a function of the underlying Window
(GLX_LEVEL <= 0).
Applications may use glXGetTransparentIndexSUN to determine whether a
transparent index is available for a particular pair of windows and to
determine the value of the transparent index.
If glXGetTransparentIndexSUN returns 1 after being called with underlay
equal to a valid window, then the transparent index is valid only for
underlay. The underlay Window must have been previously made the cur‐
rent GLXDrawable of the thread.
If a Window other than underlay is directly beneath overlay the results
of drawing with the transparentIndex are undefined.
If glXGetTransparentIndexSUN returns 1 when the underlay argument is
set to None, the transparentIndex is valid for all underlay windows.
ERRORS
A BadDrawable error is returned if overlay is not a valid Window or if
underlay is not a valid Window (except None).
NOTES
When the transparent index is valid only for a particular underlay win‐
dow, applications should follow the following guidelines to insure
proper operation: 1) It is the application's responsibility to ensure
that the only window ever underneath overlay is underlay. 2) Ideally,
overlay should be created as a child of underlay with the same size and
shape. The application should reshape the overlay window whenever the
underlay window is reshaped. This ensures that the transparent index
makes the overlay transparent.
GLXGETTRANSPARENTINDEXSUN(3glx)