[Click to run Egui web demo](https://emilk.github.io/egui/index.html). Partial demo source: <https://github.com/emilk/egui/blob/master/egui/src/demos/app.rs>
[Hobogo](https://emilk.github.io/hobogo/index.html): A small game I made using Egui. Source: <https://github.com/emilk/hobogo>
**NOTE**: Egui does not claim to have reached all these goals yet! Egui is still work in progress.
### Why Egui?
Egui is written for Rust game engines. If you are not using Rust, Egui is not for you. If you want a GUI that looks native, Egui is not for you. If you want something stable that doesn't break when you upgrade it, Egui isn't for you (yet).
But if you are writing something interactive in Rust that needs a simple GUI, Egui may be for you.
The obvious alternative to Egui is [`imgui-rs`](https://github.com/Gekkio/imgui-rs), the Rust wrapper around the C++ library [Dear ImGui](https://github.com/ocornut/imgui). Dear ImGui is a great library, which a lot more features and polish compared to Egui. However, Egui provides some benefits for Rust users:
* Egui is pure Rust
* Egui is easily compiled to WASM
* Egui lets you use native Rust String types (`imgui-rs` forces you to use annoying macros and wrappers for zero-terminated strings)
* [Writing your own widgets in Egui is simple](https://github.com/emilk/egui/blob/master/egui/src/demos/toggle_switch.rs)
Egui also tries to improve your experience in other small ways:
* Windows are automatically sized based on their contents
* Windows are automatically positioned to not overlap with each other
* Some subtle animations make Egui come alive
So in summary:
* Egui: pure Rust, new, exciting, work in progress
* Dear ImGui: feature rich, well tested, cumbersome Rust integration
* [egui_web](crates.io/crates/egui_web) for making a web app. Compiles to WASM, renders with WebGL. [Click to run the Egui demo](https://emilk.github.io/egui/index.html).
* [egui_glium](crates.io/crates/egui_glium) for compiling native apps with [Glium](https://github.com/glium/glium) backend.
* [emigui-miniquad](https://github.com/not-fl3/emigui-miniquad): backend for [Miniquad](https://github.com/not-fl3/miniquad). [Web demo](https://not-fl3.github.io/miniquad-samples/emigui.html) and [demo source](https://github.com/not-fl3/good-web-game/blob/master/examples/emigui.rs).
You need to collect [`egui::RawInput`](https://docs.rs/egui/latest/egui/struct.RawInput.html), paint [`egui::PaintJobs`](https://docs.rs/egui/latest/egui/paint/tessellator/type.PaintJobs.html) and handle [`egui::Output`](https://docs.rs/egui/latest/egui/struct.Output.html). The basic structure is this:
All coordinates are screen space coordinates, in logical "points" (which may consist of many physical pixels). Origin (0, 0) is top left.
All colors have premultiplied alpha.
Egui uses the builder pattern for construction widgets. For instance: `ui.add(Label::new("Hello").text_color(RED));` I am not a big fan of the builder pattern (it is quite verbose both in implementation and in use) but until Rust has named, default arguments it is the best we can do. To alleviate some of the verbosity there are common-case helper functions, like `ui.label("Hello");`.
Instead of using matching `begin/end` style function calls (which can be error prone) Egui prefers to use lambdas passed to a wrapping function. Lambdas are a bit ugly though, so I'd like to find a nicer solution to this.
The one and only [Dear ImGui](https://github.com/ocornut/imgui) is a great Immediate Mode GUI for C++ which works with many backends. That library revolutionized how I think about GUI code and turned GUI programming from something I hated to do to something I now enjoy.
