Completion menu rows - Clean up multi-column completion display, especially predictable height

[bobhy]

Replace PromptSession parameter reserve_space_for_menu, which wasn't really working, with a new parameter completion_menu_rows that has slightly different semantics. Additional layout fixes affecting both CompletionMenu and MultiColumnCompletionMenu noted below.

Parameter completion_menu_rows limits the number of rows that a completion menu will display, default 5. It applies equally to CompletionMenu and MultiColumnCompletionMenu. The point of putting a limit on number of rows is that it will render faster and users wouldn't read through a really long completion list anyway, they'll type a few more characters to narrow it down. Other changes ensure that the number of rows will not be reduced when at/near the bottom of the screen. The parameter can be specified on PromptSession.prompt{() or PromptSession.prompt_async() as well. Old parameter reserve_space_for_menu produces a DeprecationWarning if specified, though the value is used for the new behavior.

Other changes in the PR:

• completion.Completion.display_meta_text returns None, not empty string if Completion has no meta data. This prevents completion menus from displaying an extra blank line if no completion had meta data.
• containers.Float -- new option dont_shrink_height: bool = False. If True, height of Float will not be reduced if it wouldn't fit in FloatContainer. Instead, its preferred height will be considered in the preferred height of the FloatContainer. Default is False, the prior behavior. PromptSession layout uses this to ensure completion menus are not shrunk at bottom of screen.
• layout.MultiColumnCompletionMenu -- new option max_rows: int = 5 specifies an upper limit on number of rows in the completion menu. Similar to effect of max_height in layout.CompletionMenu. Also changed the column width calculation to handle outliers in length of completions more gracefully.

[bobhy]

Rebased on latest master. Added missing backward compatibility: reserve_space_for_menu can now be specified (but will provide the deprecation warning, as advertised).

[ju-kreber]

This works really well for me, an issue with the completion dialogue is gone (xonsh/xonsh#3843) and the behavior of space reservation is improved.

[t184256]

Can confirm that this PR solves xonsh/xonsh#3810 and makes multi tab completion ellipsize long entries.

[Spriithy]

Any chance this MR might be merged for the next release ?

[anki-code]

Hi @jonathanslenders! What do you think about this PR? Looks like many thumbups here.

[bobhy]

I'm pretty sure this PR is stale, and I don't have time to push it any more. I'm gonna close it next week unless someone wants to take it over.

[anki-code]

I think the best thing is to convert it to draft instead of closing because it will keep the chance to be discovered.