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Re: [Patch]: Allow overlay arrows to be inserted before the text at colu
From: |
Alan Mackenzie |
Subject: |
Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it. |
Date: |
Sun, 18 Aug 2019 16:15:30 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Eli.
On Sun, Aug 18, 2019 at 17:34:09 +0300, Eli Zaretskii wrote:
> > Date: Sun, 18 Aug 2019 13:48:04 +0000
> > From: Alan Mackenzie <address@hidden>
> > Currently, when there are no fringes, inserting an overlay arrow
> > overwrites the first two characters on the pertinent line. This is fine
> > for things like edebug, where the text is usually indented many columns
> > anyway, and only whitespace gets overwritten.
> > This is less good for things like compilation-mode, where this arrow
> > would obliterate the first two characters of a file name.
> > The following amendment fixes this by allowing the arrow to be displayed
> > at the BOL, displacing the rest of the line two characters to the right.
> > To do this, a new buffer local boolean variable, overlay-arrow-insert is
> > introduced.
> If you want the arrow be displayed before the line's text, why didn't
> you just put a before-string at the beginning of the line, instead of
> implementing this in the display engine?
I think it was to be able to use the same interface that the overlay
arrow already uses, without having to reimplement a lot of it using
before-strings.
> AFAIU, that would give you most of the patch for free, e.g. you
> wouldn't need to mess with the set_cursor_from_row hair.
Yes, there was set_cursor_from_row which I had to change. Somehow, only
partially initialised glyphs got into it; they pointed to lisp strings,
but with an offset of -1. This caused an error to be thrown, and the
surrounding internal_condition_case_1 reentered the redisplay code in a
loop, causing Emacs to hang. I'm not sure where they failed to get
initialised, but the function is probably better with the workaround I
put in.
> What am I missing?
Probably not a lot. Extending the overlay arrow functionality using
before-strings would certainly have been easier than changing the
display engine. But it may be worthwhile to be able to use the overlay
arrow interface for "insertion type" arrows.
--
Alan Mackenzie (Nuremberg, Germany).
- [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Alan Mackenzie, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Eli Zaretskii, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it.,
Alan Mackenzie <=
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Eli Zaretskii, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Alan Mackenzie, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Eli Zaretskii, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Alan Mackenzie, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Eli Zaretskii, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Alan Mackenzie, 2019/08/19
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Eli Zaretskii, 2019/08/19
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Noam Postavsky, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Alan Mackenzie, 2019/08/18
- Re: [Patch]: Allow overlay arrows to be inserted before the text at column zero rather than splatting it., Stefan Monnier, 2019/08/19