Manual Window Placement in i3 (Part 1)

Page Trail: [[ Manual Window Placement in i3 (Part 1) ]]
2013-05-01 00:22

I've been using tiling window managers for the past couple of years. I started with awesome, then Notion (a fork of Ion; Ion is no longer maintained), and now I'm in the process of moving to i3. For those of you that aren't familiar with it, the screenshots all look the same. They all behave differently, though, and I guess you just have to find one that fits your mental model.

When you open a new window in most tiling window managers, your existing windows get rearranged or resized to make room for it. This is kind of one main idea, actually, and it works reasonably well when opening your second or third window. Beyond two or three, depending on the screen size and applications, it starts to suck.

Awesome is a dynamic window manager, meaning it assigns each workspace a layout, and that layout determines how windows are placed as they are opened. A common layout involves a spiral of ever-shrinking window sizes. The first window opened will occupy the entire screen. The second window will take half the real estate from the first. Then the third window will take half the real estate from the second, etc.

The net result of this dynamic approach, however, is that window placement is unstable. When you launch a window (in a large enough tile to see the contents), your other windows get displaced and resized to make room. This is the single reason why I switched from awesome to Notion.

Notion's approach is very simple but powerful. Every tile is actually a tabbed set of windows. If you launch a new window, it creates a new tab in the same container. You get three commands for managing windows: split a container vertically, split a container horizontally, and unsplit. Split containers can be nested arbitrarily.

I really like Notion's basic approach. I just had a few minor gripes with Notion as a whole. Looking over my list, I don't think any are show-stoppers, and most of them I could probably fix with some configuration or minor hacks.

But I happened to come across i3, and I was impressed by the way they're managing their project. I'd recommend checking out their videos, including the lead developer's hour-long Google tech talk. Rare for these sorts of projects, it aims for well-documented code, has automated tests, and has an active community.

I was hoping i3 would work like Notion out of the box, but unfortunately their model is a bit different. i3 and Notion support the same layouts in principle: i3 splits workspaces into nested containers, where each container is either tabbed, split horizontally, or split vertically. However, i3 behaves differently when placing a new window. If you're in a tabbed container, yes, it creates a new tab. But if you're in a split container, it creates a new split, resizing your existing windows in that container. That's not what I want.

I'm not seeing any options to control this behavior, so it looks like I'm going to have to get my hands dirty and hack it up myself. Given their container model, it shouldn't be too hard in principle. I guess what I want is: if you're opening a window as part of a tabbed container, open a new tab (no change from before). If you're opening a window as part of a split container, put the current window in a tabbed subcontainer, and create the new window as a new tab there. Maybe that's it?

So I don't lose my place, the hacking howto has a couple of sections that seem relevant: "8. Manage windows (src/main.c, manage_window() and reparent_window())" and "9. What happens when an application is started?". More on this later once I've jumped into the code...

Update: part 2 explains how I set up my test environment.