2009-09-03

emacs truncate/line-wrap documentation problem

There's this variable truncate-partial-width-windows in emacs 23.1.

I think it's documentation is not very clear. I read the doc carefully, together with associated var such as word-wrap and truncate-lines. However, i cannot find out what exactly this variable do or its effects, after spending about 30 min setting various combination of values to these variables and or adjusting my frame width.

following is particular detail on why i didn't find it clear.
--------------------------------
The doc reads this:

> Non-nil means truncate lines in windows with less than the frame width.

this seems to be that this var only has effect when its val is less than frame width. So i set it to 30.

> For an integer value, truncate lines in each window with less than the
> full frame width, provided the window width is less than that integer;
> otherwise, respect the value of `truncate-lines'.

I don't see any effect. It is not clear to me what this clause means: “truncate lines in each window with less than the full frame width”. It's not clear pratically, and it's ambiguous. Does the “with less than” being a codition where this takes effect, or does it mean it is the effect of this var? Also, the emacs tradition of using “truncate lines” can probably be improved. Usually, i understand it to mean “let long lines run off the right frame width”. It does not actually _truncate_ lines. In most of today's editors, similar feature is usually called “no word wrap” or “no line wrap”. This seems much more clear to me. So, in conjunction with this report on doc issue of truncate-partial-width-windows, perhaps emacs doc would consider change the wording of “truncate” in related documentation about line wrapping.

In any case, i cannot understand what this paragraph means.

> For any other non-nil value, truncate lines in all windows with
> less than the full frame width.

> A value of nil means to respect the value of `truncate-lines'.

> If `word-wrap' is enabled, you might want to reduce this.

In short, i tried to set this to 30 or 150. 30 is less than my frame width, and 150 is more. And tried to turn on off or set to other value the other mentioned vars, but i can't see the effect.

Thanks.

Xah
∑ http://xahlee.org/



http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4334

Thanks Eli & Stefan on explaining this.

How about something like the following?

-----------------------
Documentation:
A value n sets the display to show only the first n characters per line.

This variable applies only when you have vertically split windows, and
when window width is less or equal to n.

You can customize this variable.

This variable was introduced, or its default value was changed, in
version 23.1 of Emacs.
-----------------------

Note that i removed the line “If `word-wrap' is enabled, you might
want to reduce this.”. I don't see that line appropriate, nor as
sensible suggestion. My gut feelings i'd rather want slightly larger
value of n if word-wrap is enabled.

it's not clear to me what happens when the value is something other than positive integer and is not nil. The original doc seems to suggest that has particular behavior...

Thanks.

Xah
∑ http://xahlee.org/

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