Experimental: add support for scrollbar marks

[zadjii-msft]

Adds support for marks in the scrollbar. These marks can be added in 3
ways:

• Via the iterm2 OSC 1337 ; SetMark sequence
• Via the addMark action
• Automatically when the experimental.autoMarkPrompts per-profile
  setting is enabled.

#11000 has more tracking for the big-picture for this feature, as well
as additional follow-ups. This set of functionality seemed complete
enough to send a review for now. That issue describes these how I wish
these actions to look in the fullness of time. This is simply the v0.1
from the hackathon last month.

Actions

• addMark: add a mark to the buffer. If there's a selection, use
  place the mark covering at the selection. Otherwise, place the mark
  on the cursor row.
  • color: a color for the scrollbar mark. This is optional - defaults
    to the foreground color of the current scheme if omitted.
• scrollToMark
  • direction: ["first", "previous", "next", "last"]
• clearMark: Clears marks at the current postition (either the
  selection if there is one, or the cursor position.
• clearAllMarks: Don't think this needs explanation.

Per-profile settings

• experimental.autoMarkPrompts: bool, default false.
• experimental.showMarksOnScrollbar: bool

PR Checklist

• Closes FR: IDE-style marks on scrollbar #1527
• Closes Scroll to previous/next prompt #6232

Detailed Description of the Pull Request / Additional comments

This is basically hackathon code. It's experimental! That's okay! We'll
figure the rest of the design in post.

Theoretically, I should make these actions experimental. as well, but
it seemed like since the only way to see these guys was via the
experimental.showMarksOnScrollbar setting, you've already broken
yourself into experimental jail, and you know what you're doing.

Things that won't work as expected:

• resizing, ESPECIALLY reflowing
• Clearing the buffer with ED sequences / Clear Buffer

I could theoretically add velocity around this in the TermControl
layer. Always prevent marks from being visible, ignore all the actions.
Marks could still be set by VT and automark, but they'd be useless.

Next up priorities:

• Making this work with the FinalTerm sequences
• properly speccing
• adding support for showMarksOnScrollbar: flags(categories), so you
  can only display errors on the scrollbar
• adding the category flag to the addMark action

Validation Steps Performed

I like using it quite a bit. The marks can get noisy if you have them
emitted on every prompt and the buffer has 9000 lines. But that's the
beautiful thing, the actions work even if the marks aren't visible, so
you can still scroll between prompts.

Settings blob

// actions
        { "keys": "ctrl+up", "command": { "action": "scrollToMark", "direction": "previous" }, "name": "Previous mark" },
        { "keys": "ctrl+down", "command": { "action": "scrollToMark", "direction": "next" }, "name": "Next mark" },
        { "keys": "ctrl+pgup", "command": { "action": "scrollToMark", "direction": "first" }, "name": "First mark" },
        { "keys": "ctrl+pgdn", "command": { "action": "scrollToMark", "direction": "last" }, "name": "Last mark" },
        { "command": { "action": "addMark" } },
        { "command": { "action": "addMark", "color": "#ff00ff" } },
        { "command": { "action": "addMark", "color": "#0000ff" } },
        { "command": { "action": "clearAllMarks" } },

// profiles.defaults
        "experimental.autoMarkPrompts": true,
        "experimental.showMarksOnScrollbar": true,

[zadjii-msft]

Dustin likes to keep the gifs out of the commit body:

fig 1: marks without a color change to match the default fg color

fig 2: any time you press enter, a new mark is added

fig 3: you can add bookmarks at a selection, and clear them with a selection as well

fig 4: scrolling between marks

fig 5: marks on the scrollbar, during a git log

[j4james]

I haven't reviewed in full - I was just looking at the dispatch code because I wanted to make sure it was going to work with the upcoming architectural changes.

[zadjii-msft]

• Alt buffer doesn't display marks or accept them
• It's behind velocity now

[ghost]

🎉Windows Terminal Preview v1.15.186 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Store Download

[mikemaccana]

Link above is now a 404, so: https://devblogs.microsoft.com/commandline/windows-terminal-preview-1-15-release/#scroll-marks-experimental

(have moved comments re: not being able to make scroll marks to a separate issue linked below).

[i5513]

Sorry I was using terminal stable, in preview it is ok by default, thank you!

Would be useful if autoMarkPrompts has a second option (autoMarkIncludePrompt for example) to set the mark at the same line of the command, so you can see the command and the output each time you go to next / previous mark

If you are presenting a module of powershell it would be a very useful feature, I think it is not difficult to add this case use

Thank you very much!!