hisham hm

🔗 User power, not power users: htop and its design philosophy

What the principles that underlie the software you make?

This short story is not really about htop, or about the feature request that I’ll use as an illustration, but about what are the core principles that drive the development of a bit of software, down to every last detail. And by “core principles” I really mean it.

When we develop software, we have to make a million decisions. We’re often driven by some unspoken general principles, ranging from our personal aesthetics on the external visuals, to our sense of what makes a good UX in the product behavior, to things such as “where does bloat cross the line” in the engineering internals. In FOSS, we’re often wearing all these hats at the same time.

We don’t always have it clear in our mind what drives those principles, we often “just know”. There’s no better opportunity to assess those principles than when user feedback asks for a change in the behavior. And there’s no better way to explain to yourself why the change “feels wrong” than to put those principles in writing.

Today was one such opportunity.

I was peeking at the htop issue tracker as an end-user, which is a refreshing experience, having recently retired from this FOSS project I started. I spotted a feature request, asking for a change to make it hide threads by default.

The rationale was sensible:

People casually using htop usually have no idea what userland threads are for.
People who actually need to see them can easily enable them via SHIFT+H.

With them currently enabled by default, it is very inconvenient to go through the list and see what is running, taking up RAM, CPU usage and whatnot, therefore I think it’d be more user-friendly to not show them by default.

He proceeded to show two screenshots: one with the default behavior, full of threads (in green) mixed with the processes, and another with threads disabled.

When one of the current developers said that it’s easier for the user to figure out how to hide things than for them to discover that something hidden can be shown, the counter-argument was also sensible:

Htop can also show Disk IO, which can be arguably very useful, but is hidden by default.

At that point, I decided to put my “original author” hat on to explain what was the intent behind the existing behavior. Here’s what I wrote:


Hi @C0rn3j, I thought I’d drop by and give a bit of historical background as to what was my motivation for showing threads by default.

People casually using htop usually have no idea what userland threads are for.

Yes! I fully sympathize with this sentiment. And the choice for enabling threads and painting them green was deliberate.

You have no idea how many times I was asked “hey, why are some processes green?” over these 15+ years — and no, it wasn’t annoying: each of these times it was an opportunity to teach someone about threads!


(credit: xkcd)

htop was designed to provide a view to what’s going on in the system. If a process is spawning threads like crazy, or if all your cores are overwhelmed because multiple threads of a process are doing work, I think it’s fair to show it to the user, even if they don’t know a thing about threads — or I would say, especially if they don’t know a thing about threads, otherwise these things would be happening and they wouldn’t even know where to look.

Htop can also show Disk IO, which can be arguably very useful, but is hidden by default.

One of my last projects when I was still active in htop development was to add tabs to the interface, so that the user would have a more discoverable path for navigating through these additional columns:

This code is in the next branch of the old repo https://github.com/hishamhm/htop/ — I think the code for tabs is actually finished (though not super tested); it’s pretty nice, you can click on them or cycle with the Tab key, but the Perf Counters support which I was working on, never really got stable to a point of my liking, and that’s when I got busy with other things and drifted away from development — turns out I enjoy writing interface code a lot more than the systems monitoring part!

Anyway, I think that also illustrates the pattern that went into the design: I implemented the entire tabs feature because I wanted to make IO and Perf Counters more discoverable. I wanted to put that information in front of users faces, especially for users who don’t know about these things! I considered the fact that I had implemented the entire functionality of iotop inside htop but people didn’t know about it to be a personal failure, and a practical learning experience: adding systems functionality is useless if the UI design doesn’t get it to users’ hands. (And even I didn’t use the IO features because there was no convenient way of using them.)

I never wanted to implement a tool for “super advanced Linux power users who know what they doing”, otherwise I would have never spent a full line at the bottom showing F-keys, and I would have spent my time implementing Vim bindings (ugh ;) ) instead of mouse support. I’ve always made a point that every setting can be settable via the Setup screen, which you can access via F2-Setup (shown at the bottom line!) and which you can control with the keyboard or mouse, no “edit this config file to use this advanced feature for the initiated only” or even “read the man page” (in fact it only has a man page because Debian developers contributed it!).

I wanted to make a tool that has the power but doesn’t hide it from users, and instead invites users into becoming more powerful. A tool that reaches out its hand and guides them along the way, helping users to educate themselves about what’s happening on the internals of their system, and in this way have more control of it. This is how you hand power to users, not by erecting barriers of initiation or by giving them the bare minimum they need. I reject this dicothomy between “complicated tools for power users” and “stripped-down tools for mere mortals”, the latter being a design paradigm made popular by certain companies and unfortunately copied by so many OSS GUI projects, without realizing what the goals of that paradigm really were, but that’s another rant.

And that’s why threads are enabled by default, and colored in green!

(PS: and to put the point to the proof, I must say that the tabs feature was a much bigger code change than Perf Counters themselves; it included some quite big internal refactors (there’s no “toolkit”, everything is drawn “by hand” by htop) with unfortunately might make it difficult to ressurect that code (or not! who knows?), and of course tabs are user-definable and user-editable!)


The user who proposed the change in the defaults thanked me for the history tidbits and closed the feature request. But in some sense writing this down was probably more enlightening to me than it was for them.

When I started writing htop, I did not set out to create “an instrument for user empowerment” or any such lofty goal. (All I wanted was to have a top that scrolled and was more forgiving with mistypes than circa-2005 top!) But as I proceeded to write the software, every small decision had to come from somewhere, even if done without much deliberate thought, even if at the time it was just “it felt right”. That’s how your principles start to percolate into the project.

Over time, the picture I described in that reply above became clear to me. It helped me build practical guidelines, such as “every setting must be UI-accessible”, it helped me prioritize or even reject feature requests based on how much they aligned to those principles, and it helped me build a sense of purpose for the software I was working on.

If you don’t have it clear to yourself what are the principles that are foundational to the software you’re building, I recommend you to give this exercise a try — try to explain why the things in the software are the way they are. There are always principles, even if they are not conscious to you at the moment.

(PS: It would be awesome if some enterprising soul would dig down the tab support code and ressurrect it for htop 3! I don’t plan to do so myself any time soon, but all the necessary bits and pieces are there!)


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