310 lines
15 KiB
Markdown
310 lines
15 KiB
Markdown
---
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title: "Why I Use Suckless Tools"
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date: 2020-06-05
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---
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Software is complicated. Foundational building blocks of desktop environments
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tend to grow year over year until it's difficult to understand or maintain them.
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[Suckless][suckless] offers an alternative to this continuous cycle of bloat and
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meaningless redesign. Suckless tools aim to keep things simple, minimal, usable
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and hackable by default. Their window manager [dwm][dwm] is just a window
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manager. It doesn't handle things like transparency, compositing or volume
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control. Their terminal [st][st] is just a terminal. It doesn't handle fancy
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things like ancient terminal kinds that died out long ago. It just displays
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text. It doesn't handle things that tmux or similar could take care of, because
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tmux can do a better job at that than st ever could on its own.
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[suckless]: https://suckless.org/
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[dwm]: https://dwm.suckless.org/
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[st]: https://st.suckless.org/
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Suckless tools are typically configured in C, the language they are written in.
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However as a side effect of suckless tools having their configuration baked into
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the executable at compile time, they start up _instantly_. If something goes
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wrong while using them, you can easily jump right into the code that implements
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them and nail down issues using basic debugger skills.
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However, even though the window manager is meager, it still offers places for
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you to make it look beautiful. For examples of beautiful dwm setups, see [this
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search of /r/unixporn on reddit][unixporndwm].
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[unixporndwm]: https://www.reddit.com/r/unixporn/search?q=dwm&restrict_sr=1
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I would like to walk through my dwm setup, how I have it configured all of the
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parts at play as well as an example of how I debug problems in my dwm config.
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## My dwm Config
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As dwm is configured in C, there's also a community of people creating
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[patches][dwmpatches] for dwm that add extra features like additional tiling
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methods, the ability to automatically start things with dwm, transparency for
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the statusbar and so much more. I use the following patches:
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[dwmpatches]: https://dwm.suckless.org/patches/
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- [alpha](https://dwm.suckless.org/patches/alpha/)
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- [autostart](https://dwm.suckless.org/patches/autostart/)
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- [bottomstack](https://dwm.suckless.org/patches/bottomstack/)
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- [dwmc](https://dwm.suckless.org/patches/dwmc/)
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- [pertag](https://dwm.suckless.org/patches/pertag/)
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- [systray](https://dwm.suckless.org/patches/systray/)
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- [uselessgap](https://dwm.suckless.org/patches/uselessgap/)
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This combination of patches allows me to make things feel comfortable and
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predictable enough that I can rely entirely on muscle memory for most of my
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window management. Nearly all of it is done with the keyboard too.
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[Here][dwmconfig] is my config file. It's logically broken into two big sections:
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[dwmconfig]: https://tulpa.dev/cadey/dwm/src/commit/8ea55d397459a865041b96d5b4933f426d010e6d/config.def.h
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- Variables
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- Keybinds
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I'll go into more detail about these below.
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### Variables
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The main variables in my config control the following:
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- border width
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- size of the gaps when tiling windows
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- the snap width
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- system tray errata
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- the location of the bar
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- the fonts
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- colors
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- transparency values for the bar
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- workspace names (mine are based off of the unicode emoticon `(ﾉ◕ヮ◕)ﾉ*:･ﾟ✧`)
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- app-specific hacks
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- default settings for the tiling layouts
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- if windows should be forced into place or not
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- window layouts
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All of these things control various errata. As a side effect of making them all
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compile time constants, these settings don't have to be loaded into the program
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because they're already a part of it. I use the [Hack][hackfont] font on my
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desktop and with emacs.
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[hackfont]: https://sourcefoundry.org/hack/
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### Keybinds
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The real magic of tiling window managers is that all of the window management
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commands are done with my keyboard. Alt is the key I have devoted to controlling
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the window manager. All of my window manager control chords use the alt key.
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Here are the main commands and what they do:
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| Command | Effect |
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|--------------------------------------|------------------------------------------------------------------------------------------------------|
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| Alt-p | Spawn a program by name |
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| Alt-Shift-Enter | Open a new terminal window |
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| Alt-b | Hide the bar if it is shown, show the bar if it is hidden |
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| Alt-j | Move focus down the stack of windows |
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| Alt-k | Move focus up the stack of windows |
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| Alt-i | Increase the number of windows in the primary area |
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| Alt-d | Decrease the number of windows in the primary area |
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| Alt-h | Make the primary area smaller by 5% |
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| Alt-l | Make the primary area larger by 5% |
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| Alt-Enter | Move the currently active window into the primary area |
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| Alt-Tab | Switch to the most recently active workspace |
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| Alt-Shift-C | Nicely ask a window to close |
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| Alt-t | Select normal tiling mode for the current workspace |
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| Alt-f | Select floating (non-tiling) mode for the current workspace |
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| Alt-m | Select monocle (fullscreen active window) mode for the current workspace |
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| Alt-u | Select bottom-stacked tiling mode for the current workspace |
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| Alt-o | Select bottom-stacked horizontal tiling mode for the current workspace (useful on vertical monitors) |
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| Alt-e | Open a new emacs window |
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| Alt-Space | Switch to the most recently used tiling method |
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| Alt-Shift-Space | Detach the currently active window from tiling |
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| Alt-1 thru Alt-9 | Switch to a given workspace |
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| Alt-Shift-1 thru Alt-Shift-9 | Move the active window to a given workspace |
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| Alt-0 | Show all windows on all workspaces |
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| Alt-Shift-0 | Show the active window on all workspaces |
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| Alt-Comma and Alt-Period | Move focus to the other monitor |
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| Alt-Shift-Comma and Alt-Shift-Period | Move the active window to the other monitor |
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| Alt-Shift-q | Uncleanly exit dwm and kill the session |
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This is just enough commands that I can get things done, but not so many that I
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get overwhelmed and forget what keybind does what. I have most of this committed
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to muscle memory (and had to look at the config file to write out this table),
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and as a result nearly all of my window management is done with my keyboard.
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The rest of my config handles things like Alt-Right-Click to resize windows
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arbitrarily, signals with dwmc and other overhead like that.
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## The Other Parts
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The rest of my desktop environment is built up using a few other tools that
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build on top of dwm. You can see the NixOS modules I've made for it
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[here](https://github.com/Xe/nixos-configs/blob/master/common/programs/dwm.nix)
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and [here](https://github.com/Xe/nixos-configs/blob/master/common/users/cadey/dwm.nix):
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- [xrandr](https://wiki.archlinux.org/index.php/Xrandr) to set up my multiple
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monitors and rotation for them
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- [feh](https://feh.finalrewind.org/) to set my wallpaper
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- [picom](https://github.com/yshui/picom) to handle compositing effects like
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transparency, blur and drop shadows for windows
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- [pasystray](https://github.com/christophgysin/pasystray) for controlling my
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system volume
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- [dunst](https://dunst-project.org/) for notifications
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- [xmodmap](https://wiki.archlinux.org/index.php/Xmodmap) for rebinding the caps
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lock key to the escape key
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- [cabytcini](https://tulpa.dev/cadey/cabytcini) to show the current time and
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weather in my dwm bar
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Each of these tools has their own place in the stack and they all work together
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to give me a coherent and cohesive environment that I can use for Netflix,
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programming, playing Steam games and more.
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cabytcini is a program I created for myself as part of my goal to get more
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familiar with Rust. As of the time of this post being written, it uses only 11
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megabytes of ram and is configured using a config file located at
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`~/.config/cabytcini/gaftercu'a.toml`. It scrapes data from the API server I use
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for my wall-mounted clock to show me the weather in Montreal. I've been meaning
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to write more about it, but it's currently only documented in Lojban.
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## Debugging dwm
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Software is imperfect, even smaller programs like dwm can still have bugs in
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them. Here's the story of how I debugged and bisected a problem with [my dwm
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config](https://tulpa.dev/cadey/dwm) recently.
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I had just gotten the second monitor set up and noticed that whenever I sent a
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window to it, the entire window manager seemed to get locked up. I tried sending
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the quit command to see if it would respond to that, and it failed. I opened up
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a virtual terminal with control-alt-F1 and logged in there, then I launched
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[htop](https://hisham.hm/htop/) to see if the process was blocked.
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It reported dwm was using 100% CPU. This was odd. I then decided to break out
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the debugger and see what was going on. I attached to the dwm process with `gdb
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-p (pgrep dwm)` and then ran `bt full` to see where it was stuck.
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The backtrace revealed it was stuck in the `drawbar()` function. It was stuck in
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a loop that looked something like this:
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```c
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for (c = m->clients; c; c = c->next) {
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occ |= c->tags;
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if (c->isurgent)
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urg |= c->tags;
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}
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```
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dwm stores the list of clients per tag in a singly linked list, so the root
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cause could be related to a circular linked list somehow, right?
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I decided to check this by printing `c` and `c->next` in GDB to see what was
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going on:
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```
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gdb> print c
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0xfad34f
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gdb> print c->next
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0xfad34f
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```
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The linked list was circular. dwm was stuck iterating an infinite loop. I looked
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at the type of `c` and saw it was something like this:
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```c
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struct Client {
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char name[256];
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float mina, maxa;
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float cfact;
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int x, y, w, h;
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int oldx, oldy, oldw, oldh;
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int basew, baseh, incw, inch, maxw, maxh, minw, minh;
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int bw, oldbw;
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unsigned int tags;
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int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen;
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Client *next;
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Client *snext;
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Monitor *mon;
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Window win;
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};
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```
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So, `next` is a pointer to the next client (if it exists). Setting the pointer
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to `NULL` would probably break dwm out of the infinite loop. So I decided to
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test that by running:
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```
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gdb> set var c->next = 0x0
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```
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To set the next pointer to null. dwm immediately got unstuck and exited
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(apparently my quit command from earlier got buffered), causing the login screen
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to show up. I was able to conclude that something was wrong with my dwm setup.
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I know this behavior worked on release versions of dwm, so I decided to load up
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KDE and then take a look at what was going on with [Xephyr][xephyr] and [git
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bisect][gitbisect].
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[xephyr]: https://wiki.archlinux.org/index.php/Xephyr
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[gitbisect]: https://www.metaltoad.com/blog/beginners-guide-git-bisect-process-elimination
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I created two fake monitors with Xephyr:
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```console
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$ Xephyr -br -ac -noreset -screen 800x600 -screen 800x600 +xinerama :1 &
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```
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And then started to git bisect my dwm fork:
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```console
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$ cd ~/code/cadey/dwm
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$ git bisect init
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$ git bisect bad HEAD
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$ git bisect good cb3f58ad06993f7ef3a7d8f61468012e2b786cab
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```
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I registered the bad commit (the current one) and the last known good commit
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(from when [dwm 6.2 was
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released](https://tulpa.dev/cadey/dwm/commit/cb3f58ad06993f7ef3a7d8f61468012e2b786cab))
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and started to recreate the conditions of the hang.
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I set the `DISPLAY` environment variable so that dwm would use the fake
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monitors:
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```console
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$ export DISPLAY=:1
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```
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and then rebuilt/ran dwm:
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```console
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$ make clean && rm config.h && make && ./dwm
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```
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Once I had dwm up and running, I created a terminal window and tried to send it
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to the other screen. If it worked, I marked the commit as good with `git bisect
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good`, and if it hung I marked the commit as bad with `git bisect bad`. 7
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iterations later and I found out that the [attachbelow][attachbelow] patch was
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the culprit.
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[attachbelow]: https://dwm.suckless.org/patches/attachbelow/
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I reverted the patch on the master branch, rebuilt and re-ran dwm and tried to
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send the terminal window between the fake monitors. It worked every time. Then I
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committed the revert of attachbelow, pushed it to my [NUR
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repo](https://github.com/Xe/xepkgs/commit/c3bffbc8a3ebbaf13bee60e00c8002934d89e803),
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and then rebuilt my tower's config once it passed CI.
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Being a good internet citizen, I reported this to the [suckless mailing
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list](https://lists.suckless.org/dev/2006/33946.html) and then was able to get a
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reply back not only confirming the bug, but also with [a patch for the
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patch](https://lists.suckless.org/dev/2006/33947.html) to fix the
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behavior forever. I have yet to integrate this meta-patch into my dwm fork, but
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I'll probably get around to it someday.
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This really demonstrates one of the core tenets of the suckless philosophy
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perfectly. I am not very familiar with how the dwm codebase works, but I am able
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to dig into its guts and diagnose/fix things because it is intentionally kept as
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simple as possible.
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If you use Linux on a desktop/laptop, I highly suggest taking a look at
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suckless software and experimenting with it. It is super optimized for
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understandability and hacking, which is a huge breath of fresh air these days.
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