creating true transparent widgets

[Christian Parpart]

Hi all,

I try to learn more about true (semmi-)transparent widgets using 
keith's hacked xterm:
 http://freedesktop.org/~keithp/xterm-trans.tar.gz

Thx for the link, I really had to search these source 
files very long, because I was just grepping for any 
XComposite/XTrans/XFixes/XDamage patterns;

So, as far as I understand: this source, main.c, is just passing a 
modulated ARGB pixel value to XSetWindowBackground(dpy, win, pixel);
where pixel is just the ARGB value (32bits, A upper 8bits, ..., and 
B lower 8bits).
Before passing the background pixel to XSetWindowBackground, their 
RGB value is multiplied by (A / 255); (why exactly?)
Please correct me if I'm wrong;
But as far as I do understand, this is really XComposite independant;
Okay, I do not know since when XSetWindowBackground() exists and since 
when it can be passed an alpha value, but this is the client side, and the 
server needs to interpret these alpha values and modulate the pixel values 
accordingly (to the window tree).

But if it's that easy, why is no other application using it already
(like Eterm/aterm/konsole/etc...)?

Please correct me on anything wrong/missing as I'm yet very new to the 
internals of Xcomposite and related.


Thanks in advance,
Christian Parpart.

ps: is this the right place to ask for xlib / x11 client api related coding 
questions? if not, please follow up me :)

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