Make listchars extends/precedes, fillchars lastline, and "<<<" consistent

[Asheq]

Current Behavior

When wrap is off, the characters used to show that there is text before or after the visible part of the buffer line come from the listchars flags "precedes" and "extends", respectively:

:set nowrap
:set listchars=precedes:◁,extends:▷
:set list

---

When wrap is on, the character used to show that there is text AFTER the visible part of the buffer line is "@@@" but can be overridden by thefillchars flag "lastline". And if smoothscroll is on, the character used to show that there is text BEFORE the visible part of the buffer line is "<<<" and cannot be overridden.

:set nolist
:set wrap
:set display=lastline
:set smoothscroll

:set fillchars=lastline:➤

---

And if showbreak is not empty, then "<<<" is not displayed.

:set showbreak=➥

---

And if list is on and listchars includes the "precedes" flag, then the "precedes" character is drawn on top of the showbreak character.

:set list

---

Desired Behavior

• listchars flag "precedes" should not be used when wrap is on, the same way that the listchars flag "extends" is not used when wrap is on.
• The default "@@@" should be ">>>" to match the default "<<<" on the other side. It should also be override-able by a new fillchars flag called "firstline" to be the counterpart to the existing lastline flag.

[zeertzjq]

• 'listchars' flag "precedes" should not be used when 'wrap' is on.

This is not desirable and not backward-compatible. However if a 'fillchars' "firstline" flag is added, it may make sense to give it higher priority over 'listchars' "precedes" flag.

[Asheq]

• 'listchars' flag "precedes" should not be used when 'wrap' is on.

This is not desirable and not backward-compatible.

Why is precedes used on the left side of the buffer line, but extends is not used on right side? It appears to be an oversight, not something we should intentionally preserve.

To make things consistent, we can either:

• Stop using precedes on the left side OR
• Start using extends on the right side

I preferred the first because it makes things simpler.

[zeertzjq]

• 'listchars' flag "precedes" should not be used when 'wrap' is on.

This is not desirable and not backward-compatible.

Why is precedes used on the left side of the buffer line, but extends is not used on right side? It appears to be an oversight, not something we should intentionally preserve.

It is intentional. Please see patch 8.1.2060.

[Asheq]

• 'listchars' flag "precedes" should not be used when 'wrap' is on.

This is not desirable and not backward-compatible.

Why is precedes used on the left side of the buffer line, but extends is not used on right side? It appears to be an oversight, not something we should intentionally preserve.

It is intentional. Please see patch 8.1.2060.

I also see patch 9.0.0758

I just feel that:

• Either those changes should not have been made OR
• They should have been accompanied by similar changes for "extends"

[zeertzjq]

The situation with 'showbreak' is a bit different. 'listchars' "precedes" is drawn over 'showbreak', and it doesn't disable 'showbreak' (which can be seen if 'showbreak' contains multiple characters), while 'showbreak' disables the default "<<<". If 'fillchars' "firstline" flag is added, it makes sense for it to draw over 'showbreak' as well.

[Asheq]

The situation with 'showbreak' is a bit different. 'listchars' "precedes" is drawn over 'showbreak', and it doesn't disable 'showbreak' (which can be seen if 'showbreak' contains multiple characters), while 'showbreak' disables the default "<<<". If 'fillchars' "firstline" flag is added, it makes sense for it to draw over 'showbreak' as well.

I don't think it makes sense for "precedes" to draw over showbreak characters. It doesn't give the user any more information than what showbreak already does. It just makes the UI more cluttered. That's why I proposed showbreak being the highest priority. If showbreak is non-empty, nothing else needs to be shown.

As far as the proposed fillchars "firstline" goes, I think it should actually have the same priority as the default "<<<". It's simply changing the default character, not adding another entry in the priority list. IOW, if showbreak disables the default "<<<", fillchars "firstline" should not show either. I hope that makes sense.

So, my ideal priority list would be a very simple:

1. Show "<<<" (character can be customized by 'fillchars' "firstline" flag)
2. If showbreak is non empty, disable "<<<"