"Inspired by the gaming world, we realized that the only way to achieve the performance we needed was to build our own UI framework"
I'm surprised you did not look at "Dear ImGui", "Noesis", and "JUCE". All three of them are heavily used in gaming, are rather clean C++, use full GPU acceleration, and have visual editors available. Especially JUCE is used for A LOT of hard-realtime professional audio applications.
"When we started building Zed, arbitrary 2D graphics rendering on the GPU was still very much a research project."
What are you talking about? JUCE has had GPU-accelerated spline shapes and SVG animations since 2012?
BTW, I like the explanations for how they use SDFs for rendering basic primitives. But that technique looks an awful lot like the 2018 GPU renderer from KiCad ;) And lastly, that glyph atlas for font rendering is only 1 channel? KiCad uses a technique using RGB for gradients so that the rendered glyphs can be anti-aliased without accidentally rounding sharp corners. Overall, this reads to me like they did not do much research before starting, which is totally OK, but then they shouldn't say stuff like "did not exist" or "was still a research project".
At least as far as dear imgui is concerned, it's an amazing library for dev tools but the accessibility story is dire and it has poor support for high quality typography, so it's a non starter if you're serious about good UI.
This is not to diminish the quality work that went into the library, but I passed over it for those and other reasons. I used nuklear for a bit since its typography was extensible but in the end it was too hard to overcome its other issues, so I use a custom mixed immediate/retained library now with rich text and accessibility support.
> a custom mixed immediate/retained library now with rich text and accessibility support.
I'm always interested in learning about GUI toolkits that have accessibility support. What level of accessibility support does yours have? e.g. does it implement platform accessibility APIs, and if so, on which platforms? Is your library open source? If not, can I see it in action in any commercially available product? Thanks.
I haven't found good platform accessibility API bindings for C#, so right now it just has narration support, adjustable text size/contrast, and full keyboard navigation. I'm hoping that later on in my project's development process I'll have the budget to hire someone to try and fully integrate with the platform APIs - it's designed so it will be possible by pushing updates to the retained model.
The way it works is that it has an immediate mode API (see https://github.com/sq/Libraries/blob/0ca01d949e3df5fabb1440d... for a simple example of the API) and then under the hood it uses a lightweight retained-mode graph, which means that when it's more convenient you can just write more traditional classes and components. In practice most of the UI I've written for my main project is a mix of both models, like for example an editor popup window uses IMGUI-style API while the items in a virtual listbox are represented by a small custom component.
It does have a full imgui-style layout engine under the hood instead of doing retained-mode layout, so it's able to fully re-generate layout from scratch every frame, and to minimize page tearing there is a system where components can request a second relayout pass (typically used for things like text autosize).
Here's a more complex mixed-mode example from one of my development tools: https://gist.github.com/kg/6a6ba42d5019b546858a2b18751de019
Almost all of the on-screen elements in this footage are either immediate-mode or retained-mode UI using the library: https://www.youtube.com/watch?v=ey3FtFWxbhA