Improve column selection mode

[RSeidelsohn]

With version v0.175.5, Zed recently added support for a column selection mode:

Added support for switching to columnar selection by pressing alt-shift while mouse is down

This fixates the current cursor position as starting corner of the columnar selection and uses the mouse pointer position as the ending corner. There is no way to change the starting corner other than leaving the column selection mode, repositioning the cursor and re-entering the column selection mode.

In Sublime text, this is solved in a by far superior way: With the key combination still pressed (i.e. while still in the column selection mode), the cursor can berepositioned by releasing the mouse button and pressing it again at the new position. Through this, the column selection can be modified way more flexible and easily.

I strongly vote for changing Zeds behaviour to mimic Sublime text's way of handling it. At least I use coloumn selection mode a lot.

[jrk]

I also find the multi-cursor/column selection behavior sorely lacking and much less usable than the best prior tools, but I would suggest going even farther back: I think TextMate's behavior, which SublimeText copied partially but quite incompletely, is really important.

Among other things, TextMate supports making column selections, and getting in/out of column typing mode very quickly and easily without using the mouse at all. Simply tapping the Option (Alt) key toggles any regular selection into and out of a column selection with the same bounds. This is mostly simply and commonly used to put cursors at the start of a row of lines by pressing shift-downarrow several times to select a range like this:

<some text
more text
>even more

and then tapping Option gives a "zero-column-wide" column selection, i.e. insert cursors at the start of those three lines:

|some text
|more text
|even more

This is one edge/degenerate case which behaves almost like an extra feature (like "add new cursor on line below" repeatedly), but emerges naturally and plays very intuitively with the tap-Option toggle between column/rectangular selection mode and regular/span selection mode.

I don't know why no post-TextMate editors copied this full behavior when copying the general style of TextMate in so many ways. It is much quicker and more intuitive than the equivalent functionality in anything since in the Sublime/Atom/VSCode/Zed lineage.

[jrk]

Notably, TextMate is also perfectly happy to let the column selection / multi-row cursors extend beyond the end of some of the lines. This can be useful for adding aligned content off the end of a bunch of lines.