Width of fringes

Width of fringes

[Lele Gaifax]

Hi all,

a bit of context first: just to learn something new I'm playing with the
fringe, writing my own custom minor mode to show the test coverage of each
line in a buffer; I used three different fringe symbols 'filled-rectangle,
'hollow-rectangle and 'question-mark to show respectively "executed", "missed"
and "excluded" lines of code.

Everything is going smooth, but I have a "visual glitch" that I was not able
to understand: while with standard settings (ie "emacs -Q") all three symbols
appear "complete", using my own configuration they appear "truncated" on the
left, in other words for example the 'hollow-rectangle comes out as

  xxxxxx.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  .....x.
  xxxxxx.

Looking closely, I see that the right fringe is actually a tiny bit wider that
the left one, and indeed if I put those symbols in the right fringe they come
out "complete".

I obviously checked my configuration, but nothing in it explicitly changes the
fringe-styles or whatever, and the global fringe-mode is nil, and both
left-fringe-width and right-fringe-width are nil too.

Does anybody have an hint on what could cause the different width of the two
fringes?

FWIW, I'm using Emacs master, compiled a couple of days ago, on a Debian sid.

Thanks in advance,
stay safe, ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.

Re: Width of fringes

[tomas]

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On Sat, Mar 21, 2020 at 12:18:28PM +0100, Lele Gaifax wrote:
> Hi all,
> 
> a bit of context first: just to learn something new I'm playing with the
> fringe, writing my own custom minor mode to show the test coverage of each
> line in a buffer; I used three different fringe symbols 'filled-rectangle,
> 'hollow-rectangle and 'question-mark to show respectively "executed", "missed"
> and "excluded" lines of code.
> 
> Everything is going smooth, but I have a "visual glitch" that I was not able
> to understand: while with standard settings (ie "emacs -Q") all three symbols
> appear "complete", using my own configuration they appear "truncated" on the
> left, in other words for example the 'hollow-rectangle comes out as

You can customize the "fringe-mode": it can be nil (default, 8 pixels each),
a cons of two integers (left and right fringe width) and one integer (both).

M-x customize, then search for "fringe".

Cheers
-- t

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Re: Width of fringes

[Lele Gaifax]

<tomas@tuxteam.de> writes:

> On Sat, Mar 21, 2020 at 12:18:28PM +0100, Lele Gaifax wrote:
>> Everything is going smooth, but I have a "visual glitch" that I was not able
>> to understand: while with standard settings (ie "emacs -Q") all three symbols
>> appear "complete", using my own configuration they appear "truncated" on the
>> left, in other words for example the 'hollow-rectangle comes out as
>
> You can customize the "fringe-mode": it can be nil (default, 8 pixels each),
> a cons of two integers (left and right fringe width) and one integer (both).
>
> M-x customize, then search for "fringe".

Yes, I found that, but I'd really prefer to understand why/what is causing
different widths of the left/right fringe, given that a) nothing in my
customization explicitly set neither fringe-mode, nor fringe-style, nor
left/right-fringe-width. As said, "emacs -Q" draws them with an equal width...

Thanks a lot,
ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.

Re: Width of fringes

[Eli Zaretskii]

> From: Lele Gaifax <lele@metapensiero.it>
> Date: Sat, 21 Mar 2020 14:36:07 +0100
> 
> > M-x customize, then search for "fringe".
> 
> Yes, I found that, but I'd really prefer to understand why/what is causing
> different widths of the left/right fringe, given that a) nothing in my
> customization explicitly set neither fringe-mode, nor fringe-style, nor
> left/right-fringe-width. As said, "emacs -Q" draws them with an equal width...

Maybe you've done something that made the frame width be one pixel
less.  Or maybe you did something that actually changed the fringe
width.  Bisect your customizations to see what that might be.

Re: Width of fringes

[Lele Gaifax]

Eli Zaretskii <eliz@gnu.org> writes:

> Maybe you've done something that made the frame width be one pixel
> less.  Or maybe you did something that actually changed the fringe
> width.  Bisect your customizations to see what that might be.

Thanks, will do that.

ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.

Re: Width of fringes

[tomas]

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On Sat, Mar 21, 2020 at 02:36:07PM +0100, Lele Gaifax wrote:
> <tomas@tuxteam.de> writes:
> 
> > On Sat, Mar 21, 2020 at 12:18:28PM +0100, Lele Gaifax wrote:

[...]

> > M-x customize, then search for "fringe".
> 
> Yes, I found that, but I'd really prefer to understand why/what is causing
> different widths of the left/right fringe, given that a) nothing in my
> customization explicitly set neither fringe-mode, nor fringe-style, nor
> left/right-fringe-width. As said, "emacs -Q" draws them with an equal width...

Quoth the text in "customize fringe-mode"

   "Note that the actual width may be rounded up to ensure that the
    sum of the width of the left and right fringes is a multiple of
    the frame’s character width.  However, a fringe width of 0 is
    never rounded"

I take that to mean that the fringe widths may differ by up to one
pixel. Perhaps your frame's character width is odd? (I don't know
at the moment how to get that).

Cheers
-- t

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