Implement a click handler for Meters and make the thr/kthr counters in TasksMeter toggle thread visibility

[fasterit]

Idea from Hisham in #2083 (comment)

Assisted-by: Microsoft Copilot/Claude Sonnet 4.6

[coderabbitai]

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• Header.c

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📝 Walkthrough

Walkthrough

The change adds Header_click and the Meter_Click callback contract. ScreenManager routes header-area mouse clicks through this API. TasksMeter handles text-mode clicks to toggle thread visibility and return update actions. HeaderLayout_getColumnDimensions now provides column bounds for Header_draw and Header_click.

Merge Risk: 🔵 Low · up to fe878

The PR adds header click handling and lets the thread counters toggle visibility, but when updates are paused the visible process rows may remain stale after a toggle. This is a bounded UI correctness risk that is mergeable with explicit owner awareness or follow-up.

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_{Columns align in measured rows,
A click finds where each meter goes.
Callbacks wake and settings turn,
Thread labels shift, then screens return.
The header listens, clear and bright.}

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 5

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Reviewing files that changed from the base of the PR and between 1a4504c and 5becead.

📒 Files selected for processing (5)

• Header.c
• Header.h
• Meter.h
• ScreenManager.c
• TasksMeter.c

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[BenBE]

OVerall handling LGTM; minor function split to help keep some location calculations in sync.

Unrelated note: The , text should probably be printed in teal always, not just when the element after them (thr/kthr) are active. ATM they are grey when inactive.

[hishamhm]

@fasterit I built the branch and yes, it's working! Nice!

Clicking threads on and off like this made me realize that I never kept the selection stable across these toggles (that's most noticeable in tree view). If I'm looking at a process and then enable threads, the list jumps around and I have to hunt for the process again. That was already the case when toggling via keyboard; this just made me notice it.

Implementation-wise, I understand it's a bit trickier to keep the selection stable when disabling rather than enabling: if the selection is in a process, it's easy to keep it in the same PID and have threads show up beneath it. If the current selection is a thread and one toggles threads off, then of course the selected PID disappears, so I guess the logical thing for the selection would be for it to go up to the parent process. But yeah, that would no longer be just flicking a boolean.

But then of course that's a general behavior pattern: htop doesn't preserve the selected PID when going in and out of tree view, etc. But I don't know if it's worth it: preserving the selection across toggles (without having to enable "follow") doesn't make a lot of sense unless one is in "tree view sorted by PID" (which tends to be the most stable view in terms of screen movement).

But that's just an aside, just thinking out loud about the UI behavior! The clickable Meter is already a nice improvement! Thank you!!

[fasterit]

@hishamhm: you have stable tree mode (check Setup -> Display options -> Tree view is kept visually stable) and we have much improved the Follow function (F) and there is "Sticky follow" in the Display options too which allows you to get out of Follow mode with the UP/DOWNcursor keys. Or not. That may help a bit already.

I don't think people toggle the thread views that often. But if you (or somebody else, please chime in) think differently ... we can make the view "stable" on the last PID selected.

[coderabbitai]

Actionable comments posted: 1

♻️ Duplicate comments (1)

TasksMeter.c (1)

90-99: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Refresh process rows when updates are paused.

When pauseUpdate is enabled, the requested recalculation does not call Machine_scanTables. These toggles update the setting and redraw the meter, but process rows retain the previous thread visibility until updates resume. Use the shared thread-toggle action path or refresh the process table before returning the reaction.

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📒 Files selected for processing (4)

• Header.c
• HeaderLayout.h
• ScreenManager.c
• TasksMeter.c

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[fasterit]

Stable PID re-selection has been implemented on top of this PR in #2090 .
@hishamhm and @BenBE both wanted it. 🎉