bug#6930: 24.0.50; (elisp) Layout Parameters: What is ""the standard fringe width"?

bug#6930: 24.0.50; (elisp) Layout Parameters: What is ""the standard fringe width"?

[Drew Adams]

The text says this:
 
     The default width of the left and right fringes of windows in this
     frame (*note Fringes::).  If either of these is zero, that
     effectively removes the corresponding fringe.  A value of `nil'
     stands for the standard fringe width, which is the width needed to
     display the fringe bitmaps.
 
If Lisp code wants to know how wide the left fringe is for a certain
frame, it can look at the value of parameter `left-fringe' (and at
variable `fringe-mode').  But if parameter `left-fringe' is nil, then
the fringe width is what?  It says the width is "the standard fringe
width".
 
Well, what's that?  "The width needed to display the fringe bitmaps."
Huh?  And how does it find out how wide that is for the target frame?
 
In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-08-16 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags
-Ic:/imagesupport/include'
 

bug#6930: 24.0.50; (elisp) Layout Parameters: What is ""the standard fringe width"?

[Eli Zaretskii]

> From: "Drew Adams" <drew.adams@oracle.com>
> Date: Fri, 27 Aug 2010 15:22:49 -0700
> Cc: 
> 
> The text says this:
>  
>      The default width of the left and right fringes of windows in this
>      frame (*note Fringes::).  If either of these is zero, that
>      effectively removes the corresponding fringe.  A value of `nil'
>      stands for the standard fringe width, which is the width needed to
>      display the fringe bitmaps.
>  
> If Lisp code wants to know how wide the left fringe is for a certain
> frame, it can look at the value of parameter `left-fringe' (and at
> variable `fringe-mode').  But if parameter `left-fringe' is nil, then
> the fringe width is what?

This works for me:

   (frame-parameter FRAME 'left-fringe) => 8

FRAME can be nil, meaning the currently selected frame.

Calling frame-parameter is the standard way of accessing values of
frame parameters.

So I'm closing this bug.

bug#6930: 24.0.50; (elisp) Layout Parameters: What is ""the standard fringe width"?

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> We speak here of setting the `left-fringe' parameter to nil, and
> calling `set-frame-parameter' or `modify-frame-parameters' passing nil
> for that parameter should, according to the description of those
> functions, set the value to...(drum roll) nil.  But it does not.  In
> fact, fringe params are exceptional.  "Setting" them to nil actually
> sets them to the default width, which is 8.

> Such exceptional behavior needs to be mentioned when documenting these
> fringe params

I have updated the documentation appropriately.  Thanks for the bug
report.