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List:       kde-devel
Subject:    Re: [PATCH] Transparency support and bugfixes
From:       Jo Dillon <emily () thelonious ! new ! ox ! ac ! uk>
Date:       1999-02-22 18:38:19
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Timothy Whitfield (timothy@datasync.com) spake thusly:

> Why do we need letters? They don't look cool. ;-)
> 
> Ok we are about to find out exactly how much I don't know about X.
> 
> <IMHO>
> It seems as if we are saying that X uses the reverse-painters algorythm as
> far as sending rect updates, only in this case we want to use the painters
> algorythm.  So in order to do this we have to use a non-transparent widget
> like currently implemented in order for kwmbgnd not to paint over our
> letters.
> 
> But is there any reason why we can't force kwmbknd to update before we do,
> by sending a rect update to applications behind the window
> with the transparency and then put the letters on?
> 
> Note: I did not volunteer as I am not even sure whether what I am saying
> is possible, or just shows my ignorance about X message processing.
>  </IMHO>

  X quite simply doesn't work this way. X has a hierarchical group of
windows (so a button is a window inside a top-level app window) and you
draw into those windows. If another window is over the top, it doesn't
get drawn over. So kwmbknd /cannot/ overwrite what's in the application
windows, since it's painting on the root window. It can't happen. No way.
(at least, not with normal X commands - you could muck around with
XFree's DGA extension or something, but X doesn't really provide the
support you'd need).

-- 
	Jo

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