Re: [rudalics@gmx.at: enlarge-window with preserve-before non-nil]

["Jan D." <jan.h.d@swipnet.se>]

Richard Stallman wrote:

>Can someone please investigate this, and ack?
>  
>

I looked a bit, but I am not sure how it shall work.  If I just to three 
windows, in the obvious way (C-x 2, C-x 2), I get three windows, one 11 
lines, one 12 lines and one 24 lines.  This gives me this window 
configuration:

0x86b6b10: vchild: 0x861d830, hchild: 0x0, next: 0x861d9c8, parent: 0x0, 
h: 47
0x861d830: vchild: 0x0, hchild: 0x0, next: 0x8694a50, parent: 0x86b6b10, 
h: 11
0x8694a50: vchild: 0x0, hchild: 0x0, next: 0x86b6ca8, parent: 0x86b6b10, 
h: 12
0x86b6ca8: vchild: 0x0, hchild: 0x0, next: 0x0, parent: 0x86b6b10, h: 24
0x861d9c8: vchild: 0x0, hchild: 0x0, next: 0x0, parent: 0x0, h: 1

But if I create the same three windows (11, 12 and 24 lines) with the 
method below, I get this window configuration:

0x8833558: vchild: 0x87f9978, hchild: 0x0, next: 0x861d9c8, parent: 0x0, 
h: 47
0x87f9978: vchild: 0x86a7a48, hchild: 0x0, next: 0x8820a48, parent: 
0x8833558, h: 23
0x86a7a48: vchild: 0x0, hchild: 0x0, next: 0x87b6d68, parent: 0x87f9978, 
h: 11
0x87b6d68: vchild: 0x0, hchild: 0x0, next: 0x0, parent: 0x87f9978, h: 12
0x8820a48: vchild: 0x0, hchild: 0x0, next: 0x0, parent: 0x8833558, h: 24
0x861d9c8: vchild: 0x0, hchild: 0x0, next: 0x0, parent: 0x0, h: 1

When enlarge-window shall enlarge a window (the one with 12 lines in 
this case), it calculates the maximum lines it can enlarge it to.  Since 
enlarge-window gets called with PRESERVE_BEFORE set to t, in the first 
case this is:
 47 (the parent) - 11 (the sibling to preserve) = 36 (> 12, i.e. enlarge 
is OK).

In the second case:
 23 (the parent) - 11 (the sibling to preserve) = 12 (i.e. can not enlarge).


If the window trees shall be the same, there is a bug in adding/removing 
windows, as the extra 23 line parent then should be removed.  But it may 
be a bug in enlarge-window also, it should in the second case use the 
topmost parents height.

    Jan D.

>------- Start of forwarded message -------
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>Date: Sun, 01 May 2005 14:21:26 +0200
>From: martin rudalics <rudalics@gmx.at>
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>To: emacs-pretest-bug <emacs-pretest-bug@gnu.org>
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>Subject: enlarge-window with preserve-before non-nil
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>Suppose I start with a single window called W1 (window names are
>fictional)
>
>W1
>
>split W1 horizontally
>
>W1 | W2
>
>split W2 vertically
>
>    | W2
>W1 |---
>    | W3
>
>delete W1
>
>W2
>- --
>W3
>
>split W2 horizontally
>
>W2 | W4
>- -------
>    W3
>
>split W4 vertically
>
>    | W4
>W2 |---
>    | W5
>- -------
>    W3
>
>and delete W2
>
>W4
>- --
>W5
>- --
>W3
>
>At this moment I can't enlarge W5 any more by "dragging its modeline
>down" - the window configuration appears "frozen".  The attempt to
>shrink W5 by dragging its modeline "up" has an effect similar to that of
>dragging W4's modeline down, that means, W4 gets enlarged and not W3.
>Likely, in this scenario siblings got confused before issuing the call
>to `enlarge-window' with PRESERVE-BEFORE non-nil.
>
>
>
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