Fix Console Scrolling

[parisa-mchp]

What it does

Fixes autoscrolling functionality in debug console. How this should work, is if the console is scrolled to the bottom, then when new content is output, it should be shown automatically, but if the user scrolls up, the view should stay put.

How to test

This functionality can be tested with any debuggable project. For example I used the cpp-debug-workspace, which after installing cdt-gdb-vscode, can be debugged following the instructions in the README.md file. To test, place a breakpoint within the main loop i.e. a.cpp:35. Allow the debugger to continue a few times. Each time it does, any new output to the debug console should be shown automatically. Then, scroll up a few lines and continue a few more times. Now the view should remain fixed.

Explanation

Here's how it worked previously:

When ConsoleContentWidget.model.onChanged() is fired, this triggers 3 notable events: ConsoleWidget.revealLastOutputIfNeeded, TreeWidget.updateScrollToRow, and TreeWidget.updateRows usually in that order. revealLastOutputIfNeeded uses the selection service to focus the newly added node. Next, updateScrollToRow attempts to find the row corresponding the the focused node, and fails to find it and thus doesn't scroll. Finally, after that happens updateRows creates the corresponding row.

Furthermore, the logic to determine when the console should be scrolling or not uses the onScrollUp, and onScrollYReachEnd methods, which don't appear fire for tree widgets (they work for other widgets). I believe this is because it's not the root widget container that is scrolling, but one of it's child elements, but wasn't able to figure this out.

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[parisa-mchp]

Would it be good to also remove the onScrollReachEndEmitter and onScrollUpEmitter? Those appear to have been added specifically for this use case.