[forum] X-Transparency

[Scott Brumbaugh]

Hi,

I saw that window translucency is on the X 5.0 TODO list so I thought
I would post this message for anyone who is interested in this
particular topic.

A few months ago I used XDirectFB to develop an experimental X
protocol extension called X-Transparency.  This extension allows any
xclient to control the opacity of its or any other x client's top
level x window.  The extension is general and requires that an Xserver
provide callbacks to the protocol to control a top-level window's
transparency.  With XDirectFB these callbacks are simple wrappers
around the corresponding DirectFB api calls.

The X-Transparency API is pretty simple, you use 

    XSetOpacity( dpy, win, value );

to change a windows opacity, and

    XGetOpacity( dpy, win, &value );

to get it.  The extension is available in the directfb cvs under
XDirectFB/xc-transparency-extension.diff

More recently, I have patched the Sawfish window manager to use this
extension.  With this patched Sawfish, a user can continuously vary
window transparency by ctrl-mouse dragging on the title bar of any x
window.  I picked Sawfish for this prototype because it was relatively
easy to write librep wrappers around the XGet/XSetOpacity calls.
After that it was also easy to write lisp functions to change window
transparency and bind these to mouse events.

Here is a pointer to the original X-Transparency extension patch which
is obsoleted by the current xdirectfb cvs:

http://directfb.org/mailinglists/directfb-dev/2002/12-2002/msg00136.html

Here is a pointer to the latest Sawfish patch, this patch is not in cvs:

http://directfb.org/mailinglists/directfb-dev/2003/03-2003/msg00133.html


Scott Brumbaugh