[feature] New tab indicator in omni bar

[ckardaris]

• Add omni bar mode indicator to the left of the input field.
• Add new tab indicator '+' if the omni bar action will be completed in
  a new tab.
• Provide shortcut (alt + n) to switch between current tab and new tab
  mode.
• Provide shortcut (alt + m / alt + M) to cycle over the available omni
  bar completers.

Description

Good evening. This MR is a POC related to #4509.

The proposed design changes may be deemed too radical, but I am submitting them here for discussion.

Change no. 1
The omni bar "mode" is shown to the left of the input field. Shortcuts Alt + m/M are used to cycle through modes (the input text is preserved). This can be useful if you realize you need to search in another mode and don't want to lose text input or press Esc + <correct shortcut>.

Change no. 2
A plus sign + is added next to the name of the mode if the selected action will be opened in a new tab (not counting with any modifier shortcuts like Shift + Enter. The shortcut Alt + n is used to switch this current tab / new tab mode.

[philc]

One thing I don't love about this implementation is that the query's text input and the results aren't on the same vertical grid line.

As part of merging #4880, in 37e6c09, I used the placeholder text in the Vomnibar to show which completion mode you're in. This work well for tabs, bookmarks, commands. The default case (omni) shows no placeholder.

[philc]

I also think the "+" sign is too opaque of an indicator of what's going to happen.

Here's a rough mock of a more self-evident alternative:

Nothing would be shown on the right when the result is going to be opened in the same tab. It could instead say "Open in new tab" to be even more self-evident.

[ckardaris]

One thing I don't love about this implementation is that the query's text input and the results aren't on the same vertical grid line.

As part of merging #4880, in 37e6c09, I used the placeholder text in the Vomnibar to show which completion mode you're in. This work well for tabs, bookmarks, commands. The default case (omni) shows no placeholder.

I like that. It is elegant and avoid the flickering when the bar is launched.

I also think the "+" sign is too opaque of an indicator of what's going to happen.

Here's a rough mock of a more self-evident alternative:

Nothing would be shown on the right when the result is going to be opened in the same tab. It could instead say "Open in new tab" to be even more self-evident.

This suggestion also looks nice. I will take a crack at it.

@philc What do you think about the mode changing shortcuts? Alt+m/M and Alt+n?

[philc]

I personally wouldn't find those mode changing shortcuts useful, and they're hard to decide on and document. Finally, I don't think Vim has a conceptual analog that we can use as a reference.

[ckardaris]

I personally wouldn't find those mode changing shortcuts useful, and they're hard to decide on and document. Finally, I don't think Vim has a conceptual analog that we can use as a reference.

Understood. Let's keep it simple.

[ckardaris]

@philc I have pushed an attempt of implementing your suggestion. Let me know what you think.