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111 lines
4.2 KiB
Markdown
111 lines
4.2 KiB
Markdown
# widgetry notes
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Rustwarts School of Glitchcraft and Widgetry.
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This is a GUI + 2D drawing + data viz library I've built up for A/B Street. I'm
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considering cleaning up the API surface and making it a proper standalone crate.
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## Running the demo
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Because of wasm-pack issues, normal Rust example binaries don't work. The
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example code is instead in the
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[widgetry_demo crate](../widgetry_demo/src/lib.rs).
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```
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git clone https://github.com/a-b-street/abstreet.git
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cd abstreet/widgetry_demo
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cargo run
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# Or for web
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cd abstreet/widgetry_demo
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./run_web.sh
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```
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If you want a more thorough idea of what this crate can do, see
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[A/B Street](https://abstreet.org).
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## Features
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### Runs in lots of places
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Runs on Linux, Mac, Windows via [glow](https://github.com/grovesNL/glow/). Also
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works in the browser using WebAssembly, but text support still coming in
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[a few months](https://github.com/RazrFalcon/resvg/issues/229).
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Why OpenGL? My requirements are super simple; I don't need the power of Vulkan
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or other new stuff. I want something simple that runs everywhere. If you want to
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make this work with WGPU or something else, it should be easy. The backends are
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a few hundred lines -- [Glow](src/backend_glow.rs) running either
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[on native](src/backend_glow_native.rs) or [on wasm](src/backend_glow_wasm.rs).
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### 2D drawing
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Everything is a colored polygon. Upload stuff once, redraw many times with a
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simple camera transform. Panning and smooth zooming. One extremely simple
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shader.
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Thanks to [usvg](https://github.com/RazrFalcon/resvg) and
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[lyon](https://github.com/nical/lyon/), SVGs and text are transformed into
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colored polygons. Programatically swap colors, rotate, scale stuff. Find bounds
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for precise mouseover.
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### GUI
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Widgets like buttons (with keybindings), checkboxes, sliders, pop-up menus, text
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entry, and some data viz things. You can combine these in `Panel`s to dispatch
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event handling and drawing. Styling (background colors, outline, padding) and
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Flexbox-ish layouting via [stretch](https://vislyhq.github.io/stretch/).
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The API / programming style is kind of funny; see the
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[demo](../widgetry_demo/src/lib.rs) to get a sense of it. No callbacks. You
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manually feed events into your `Panel`s of widgets and ask about what happened.
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There's no smart diffing of widget trees; most of the time it's fine to
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completely recreate a `Panel` from scratch when something changes, or replace a
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single widget in an existing `Panel`.
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(This is not a performance critical library. The perf bottlenecks in A/B Street
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are not in the GUI, and I probably won't invest much time speeding things up
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here until they are. (Or if somebody else winds up using this library and hits a
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problem.))
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### Data visualization
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Not exactly sure how this wound up in here too, but at some point I needed
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histograms and line plots that update live over time and show some info when you
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mouseover points, so here it is.
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## Big problems to solve before release
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When you ask a `Panel` what action happened (what button was clicked), it hands
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you back `Option<String>`. Not so typesafe. How boilerplatey is it to associate
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buttons with a user-provided enum?
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There are hardcoded colors / padding in lots of places. Need to make style
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easily configurable, with good defaults.
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The error handling is pretty bad; lots of unwraps and panics to clean up.
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When returning a `Transition::Replace`, ideally we can consume `self` instead of
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just having `&mut self`, so we can avoid cloning stuff from one `State`.
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## Why another Rust GUI library?
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When I started, nothing did what I needed, or it required awkward callbacks.
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Today, [iced](https://github.com/hecrj/iced) looks awesome, but wgpu doesn't
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work on my laptop. This is a dealbreaker -- I want to build stuff that runs
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~anywhere. I looked into adding an OpenGL backend, but the current structure of
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iced has a
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[huge](https://github.com/hecrj/iced/blob/master/native/src/renderer/null.rs)
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API surface to implement for a new backend.
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For the moment, I don't have enough time to get something else on-par with this
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library and port A/B Street over, so I'll continue to invest in this library. If
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there's lots of interest in other people using this library, I'll invest much
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more and make it a real contender.
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## Future work
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- Draggable panels
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