Fix shift selection in vi (insert) & emacs mode

[collinmurch]

This PR fixes shift selection in vi (insert) & emacs mode. The gist is that we were incorrectly selecitng an additional character when selecting leftwards (holding shift and pressing left arrow). One extra character to the right of the start location was getting highlighted and would be affected by any delete or other operations.

Tested on macOS with both vi & emacs mode. No regression of vi (normal) shift selection functionality.

Fix for this issue: #922 which I think is a duplicate of #893.

[blindFS]

Thanks, that seems similar but clearer than the solution by Claude #911 .

Noticed one minor issue, steps to reproduce:

1. selection done in vi normal mode
2. press c, the last selected character is not deleted.

[collinmurch]

Yeah, you're totally right; I missed this test case. Should be fixed now, all the modes seem to work for me.

[blindFS]

Yeah, you're totally right; I missed this test case. Should be fixed now, all the modes seem to work for me.

Your last commit didn't change anything in my setup. Say I have abcdefg in cli with cde selected in vi normal mode.
After pressing c, the result is ab|efg where | represents the cursor.

[blindFS]

There's another complication: inconsistent behavior of selection in vi normal mode triggered by v or shift + arrow key.
A common issue for #911

[collinmurch]

Okay I pushed up a commit that actually does fix it. My prior one did fix shift selection going leftwards but seems to have just shifted the issue to being present moving to the right for vi normal mode + cut operations. This new commit fixes it for both, but adds some complexity that I don't love.

The core issue is that when we perform the cut operation, we immediately go into insert mode which then messes up the calculation for text to delete. Since we're in insert mode, it selects one character short even though the selection was made with vi normal mode.

Let me know what you think of this. Also, I'm not sure exactly what you're referring to with:

There's another complication: inconsistent behavior of selection in vi normal mode triggered by v or shift + arrow key.

From my experience, I can't even get the two to behave the same on a fresh build of the main branch. It seems that shift selection for vi normal mode has some other bug that makes it operate inconsistently with the cut and other operations.

[blindFS]

There's another complication: inconsistent behavior of selection in vi normal mode triggered by v or shift + arrow key. A common issue for #911

Yeah I noticed this too but in my testing the same behavior is present in the current build of main. So I think it might be unrelated. Let me know if you disagree.

Yeah, probably rooted elsewhere. OMG...

[blindFS]

I used to take this issue to test AI agents' capabilities, haha. Never found one that's good enough. Claude 4.0 >> Gemini 2.5 pro on this issue, but still lame.

[collinmurch]

Yeah since I'm new to this repo claude 4 has helped out with some of this but ultimately I'm having to babysit it pretty aggressively. Keeps wanting to implement hacky one-off fixes.

[collinmurch]

Any movement on this?