Smart scroll: Add scroll position behavior alongside cursor position

[Copilot]

Smart scroll in the Output view originally locked/unlocked based on cursor position. This PR adds scroll-based unlocking while retaining the original cursor-based behavior, providing users with two ways to re-enable auto-scrolling.

Changes

outputView.ts

• Retain onDidChangeCursorPosition listener for original cursor-based behavior
• Add onDidScrollChange listener for new scroll-based behavior
• Check scrollTopChanged to filter horizontal scroll events
• Both behaviors work together: unlock by clicking last line OR scrolling to bottom
• Lock logic for scroll: scrollLock = !(scrollTop + viewportHeight >= scrollHeight)

output.contribution.ts

• Update setting description to reflect both cursor and scroll-based behaviors

outputView.test.ts

• Add unit tests for scroll lock states at different positions

Implementation

Both listeners now coexist:

// Original cursor-based behavior
this._register(codeEditor.onDidChangeCursorPosition((e) => {
    if (e.reason !== CursorChangeReason.Explicit) return;
    if (!this.configurationService.getValue('output.smartScroll.enabled')) return;
    
    const model = codeEditor.getModel();
    if (model) {
        const newPositionLine = e.position.lineNumber;
        const lastLine = model.getLineCount();
        this.scrollLock = lastLine !== newPositionLine;
    }
}));

// New scroll-based behavior
this._register(codeEditor.onDidScrollChange((e) => {
    if (!e.scrollTopChanged) return;
    if (!this.configurationService.getValue('output.smartScroll.enabled')) return;
    
    const layoutInfo = codeEditor.getLayoutInfo();
    const isAtBottom = e.scrollTop + layoutInfo.height >= e.scrollHeight;
    this.scrollLock = !isAtBottom;
}));

Users can now unlock auto-scrolling by:

1. Clicking on the last line (original behavior)
2. Scrolling to the bottom (new enhancement)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Smart Scroll: Unlock when scrolling down to the last line</issue_title>
<issue_description>I would like to propose to improve the useability of smart scroll.
If I have a lot of console output, it is nice that it automatically locks the scrolling so I can read an output.
But if I then want to unlock and see the newest output its quite inconvenient having to click that last line or click the lock icon.

Feature request: Unlock when scrolling down to the last line.

With this solution, there would be no need to click anything. Just scrolling with the mouse would do all the work.

</issue_description>

<agent_instructions>Check this comment on what to implement

#127063 (comment)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@roblourens I was about to file the same issue, and I think this should be assigned to @sandy081, just checking. Some more motivation:

• Open output channel
• cmd+f, find something
• The output channel editor scrolls to the match
• Then more output loads, and it scrolls back to the bottom

Put another way, I think that smart scroll should not be based on the cursor position, but on the editor scroll position, and it should be enabled when I scroll to the bottom and disabled when I scroll up.</comment_new>

• Fixes Smart Scroll: Unlock when scrolling down to the last line #127063

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[sandy081]

@copilot Retain the old behaviour - which is using cursor position at the end

[Copilot]

@copilot Retain the old behaviour - which is using cursor position at the end

Restored the original cursor-based behavior alongside the scroll-based behavior. Both now work together - users can unlock by clicking the last line (original) or by scrolling to the bottom (new). (b5a7478)