emacs: Split wide window vertically for tree mode message pane

[Prof Jayanth R Varma]

On Wed, May 09 2018, David Bremner wrote:

> Prof Jayanth R Varma <jrvarma at gmail.com> writes:

>> This patch modifies the function notmuch-tree-show-message-in 
>> in notmuch-tree.el to split the window vertically while 
>> creating a message pane in tree-mode if the window is wider 
>> than 160 (so that after splitting, the message pane can show 
>> the standard 76 character plain text email lines without 
>> wrapping).

> 2) I noticed that the horizontal splitting leads to truncation 
> of tag display. So I think not everyone will want this (it would 
> be pretty frustrating to widen the emacs frame to see a full tag 
> list, just to have it truncated). One option would be to control 
> the splitting by a variable specifying the minimum width at 
> which to switch to horizonal splitting.

I agree that the customization option is superior to my original 
patch. The default value of the customization variable could be 
set equal to the emacs variable "most-positive-fixnum" (the 
largest value that is representable in a Lisp integer) so that the 
patch would not have an impact for anybody who does not explicitly 
customize it.

> 3) The commit message / NEWS talks about splitting the window 
> vertically, but that seems contrary to the emacs terminology (as 
> evinced by the source code in the patch)

My mistake: vertically should be changed to horizontally in the 
commit message, NEWS and source code comments.