Replacing a window icon in X11?

[Lubos Lunak]

On Thursday 02 of April 2009, Glynn Clements wrote:
> Wirawan Purwanto wrote:
> > Today most window managers has an area on the top left corner of the
> > window decoration which shows a small bitmap, which in Windows world
> > called "icon". I wonder if there is any way for an external program, if
> > it knows the window ID of a given X11 window, to change that image to
> > something else.

> The property in question is WM_HINTS, which is set using the
> XSetWMHints() function. The property contains multiple fields, so in
> order to preserve any existing hints, you would need to read the
> existing value with XGetWMHints(), modify it, then write the updated
> value.

 Nowadays it is actually mostly the _NET_WM_ICON hint from the EWMH spec. 
Toolkits generally have functions for changing it, although it's a question 
if they can do it for foreign windows (no idea about Gtk, Qt can't, KDE's 
NETWinInfo::setIcon() can).

> But as Daniel suggests, most window managers provide a mechanism to
> override a window's icon (or lack of one).

 I doubt that's the case, especially when interpreting 'most' as 'most people 
use'. Still, adding this if necessary should be the best option, given what's 
below.

> This would normally be 
> preferable to modifying the WM_HINTS property. Apart from anything
> else, it's possible that your changes will be discarded whenever the
> application (or WM) updates the WM_HINTS property.

-- 
Lubos Lunak
KDE developer
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