[Tcl-bugs] [ tktoolkit-Patches-2475855 ] Stop grid/pack from handling the same master

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Patches item #2475855, was opened at 2008-12-29 23:31
Message generated for change (Comment added) made by avl42
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Category: 48. Geometry Management
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Peter Spjuth (pspjuth)
Assigned to: Peter Spjuth (pspjuth)
Summary: Stop grid/pack from handling the same master

Initial Comment:
The attached patch is a way to give an error message
when grid and pack are used in the same master.
Currently this can lead to an application and possibly
the desktop to hang. Such bugs are hard to debug.

Is there any possibility for a working usage of
propagating pack and grid in the same master?
If there are, this could be a compatibility problem,
but I cannot imagine such a usage.


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Comment By: Andreas Leitgeb (avl42)
Date: 2008-12-30 12:56

Message:

Two propagating GMs should be possible, if neither of the GMs can ever
reflect a size-change from the master back to the master. If one GM has a
new child added and propagates the change to the master, then the other GM
just sees the change and must not change it back in the course of
reconfiguration. If the second GM then also has a child added, then it has
its turn at resizing the master. 

How would such an approach fail?

(I haven't yet looked at the patch, so I don't know what strategy it
actually implements.)


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Comment By: Nobody/Anonymous (nobody)
Date: 2008-12-30 02:41

Message:
Looks like this patch is generally on the right track, a couple quick
notes:

+ Don't extend struct Tk_FakeWin (this should be left alone, it needs to
go away);
+ Probably not a good idea to use Tk_UIDs as the GM identity token; ...

Re: "[working] propagating pack and grid in the same master" -- AFAICT no,

this always breaks, ergo by definition no working program does this. 
(Although it
is possible to [pack] and [grid] two widgets into the same master without
wedging,
this is a perverse situation and it only works by accident.)

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Comment By: Donal K. Fellows (dkf)
Date: 2008-12-30 00:12

Message:
I really don't think that you can ever have two propagating GMs on the same
master. Each will detect the changes by the other and try to resize the
master in response --> infinite loop...

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