feat: implement smart scroll for terminal output

[dzw1995]

Implement smart scrolling behavior that only auto-scrolls when user is already at the bottom of the terminal. This allows users to scroll up and view history without being forced back to the bottom when new output arrives.

Changes:

• Add isAtEndOfOutput() method to QTermWidget
• Modify onQTermWidgetReceivedData() to check user position before scrolling
• Improves experience with high-frequency output apps like kimi-cli
• Enhanced debug logging for scroll behavior

Fixes: Users can now scroll up to view history while output is ongoing

[github-actions]

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[deepin-ci-robot]

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[github-actions]

Note

[静态代码检查]

• 敏感词检查失败, 检测到1个文件存在敏感词

详情

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[github-actions]

Note

[静态代码检查]

• 敏感词检查失败, 检测到1个文件存在敏感词

详情

{
    "src/views/termwidget.cpp": [
        {
            "line": "    QString strUrl = \"https://cn.bing.com/search?q=\" + selectedText();",
            "line_number": 701,
            "rule": "S35",
            "reason": "Url link | fd576f862d"
        },
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            "rule": "S35",
            "reason": "Url link | 6f8d292d20"
        },
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            "rule": "S35",
            "reason": "Url link | e1ba2d7c70"
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}

[wyu71]

Thanks for the contribution! The smart scroll feature is a reasonable improvement. However, there's a logic issue in the current implementation that prevents it from working correctly. Please revise and resubmit.

Core Issue

In termwidget.cpp onQTermWidgetReceivedData, the setTrackOutput logic is flawed:

// Current code (broken)
if (getIsAllowScroll()) {
    setTrackOutput(Settings::instance()->OutputtingScroll()); // 1. Unconditionally sets true
    if (isAtEndOfOutput()) {
        setTrackOutput(true);   // 2. Redundant
    } else {
        // 3. Missing setTrackOutput(false) — the true from step 1 already took effect
    }
}

Problems:

1. The first line setTrackOutput(OutputtingScroll()) already sets trackOutput to true
2. When user is not at the bottom, the else branch doesn't call setTrackOutput(false), so auto-scroll is never actually prevented
3. When user is at the bottom, setTrackOutput(true) is called twice redundantly

Suggested Fix

if (getIsAllowScroll()) {
    setTrackOutput(isAtEndOfOutput());
    setIsAllowScroll(true);
}

This one-liner setTrackOutput(isAtEndOfOutput()) does the job: auto-scroll when at the bottom, hold position when scrolled up.

Minor Suggestions

• The 6 qCDebug logs for a simple boolean check are excessive — consider trimming
• setIsAllowScroll(true) is called in both branches, can be moved outside the if-else
• The comment style in qtermwidget.h should follow the project's existing full comment block format (with author/date)

[wyu71]

Review of fix commit (bce585c)

Thanks for addressing the previous feedback. The one-liner setTrackOutput(isAtEndOfOutput()) is much cleaner and the core smart scroll logic is now correct.

Remaining issue: OutputtingScroll() check was removed

The original code guarded against the user disabling scroll-on-output in settings:

if (!Settings::instance()->OutputtingScroll()) {
    setIsAllowScroll(true);
    return;
}

This was removed in the fix commit, which means smart scrolling now takes effect regardless of the user's OutputtingScroll preference. We should keep this check.

Suggested final version

inline void TermWidget::onQTermWidgetReceivedData(QString value)
{
    qCDebug(views) << "Enter TermWidget::onQTermWidgetReceivedData";
    Q_UNUSED(value)

    if (!Settings::instance()->OutputtingScroll()) {
        setIsAllowScroll(true);
        return;
    }

    // Smart scroll: auto-scroll only when at bottom, hold position when scrolled up
    if (getIsAllowScroll()) {
        setTrackOutput(isAtEndOfOutput());
        setIsAllowScroll(true);
    }
}

Minor: comment date typo

In qtermwidget.cpp, the comment above isAtEndOfOutput() says 2025-03-26, should be 2026-03-26.

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: dzw1995, lzwind

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