[Perlplusplugin-developers] More on X-events

[Frank H. <fh...@av...>]

Dmitry,
Here's the Perl program I was using to learn how X works and to
experiment with preserving a window while Netscape resizes.  The idea
was to trap the ResizeRedirect and SubstructureNotify events before the
destroy happened, reparent the window and it's descendants outside the
Netscape heirarchy and then reparent them back into the heirarchy once
Netscape had settled down from the resize.

Note that I view trees of this sort as inverted, so the root node is at
the top and the leaves are at the bottom.  'Up' means toward the root
node and 'down' means toward the leaves.

Yesterday, I indicated that events propagate up the tree, but I think
that's incorrect.  Most event notifications are propagated down the
tree, so I set masks on windows a few levels above the embedded window.
However, destroys happen from the bottom up, obviously.

This code successfully preserves the Perl/Tk windows most of the time,
but not quite all the time.  I attribute this to the fact that it
sometimes loses the race with the X-server, but I don't know a way yet
to prove that's what happens.

An alternative to this approach is to have the Perl program detect the
destruction of it's children and reconstruct them.  I haven't
experimented with this yet.  It might be tricky for windows displaying
rapidly changing data -- scrolling text, for example -- since you'd want
to restore to the exact place in the text where the destroy occurred.

Maybe widgets could be designed to respond to X-events and preserve
enough state to make such reconstructions easier.

-- 
-------------------------------------------------------------------------------
| Frank Holtry           | "If you have the right attitude, interesting       |
| fh...@av...      |  problems will find you."                          |
|                        |                            Eric S. Raymond         |
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