EFx

EFx — Rust 🦀 XML Template Engine for eframe / egui framework. efx! is a proc-macro for writing tiny XML-like UI snippets in eframe/egui. It converts short tags into egui calls.

You can embed arbitrary Rust expressions inside braces ({...}).

Install & import

Requires eframe/egui (the project currently uses eframe 0.32). Add to Cargo.toml:

[dependencies]
efx = "0.4"
eframe = "0.32"

Inside this repo just import the macro:

use efx::efx; // the macro

Quick start

<Label>…</Label>

Renders a text Label. Returns () (equivalent to ui.Label(...)).

efx!(ui, r#"<Label>Hello, world</Label>"#);

// With interpolation:
let status = "ready";
efx!(ui, r#"<Label>Status: {status}</Label>"#);

<Button>…</Button>

Renders a button. Returns egui::Response (so you can check clicks).

if efx!(ui, r#"<Button>Run</Button>"#).clicked() {
    // handle click
}

Note: tag names are case-sensitive.

Expression interpolation {...}

Inside tag content you can insert any Rust expression that implements Display:

let a = 2;
let b = 3;
efx!(ui, r#"<Label>Sum: {a + b}</Label>"#);

Escaping braces

To print { or }, use double braces (same as format!):

efx!(ui, r#"<Label>Literals: {{ and }}</Label>"#);

Errors & diagnostics

At compile time the macro parses your snippet; at runtime it shows readable diagnostics via ui.Label(...) when input is invalid:

• Unknown tag Output: Unknown tag: <TagName>

• Mismatched open/close tags Output: Mismatched tags: <open> and </close>

• Interpolation count mismatch Happens if the parser found e.g. two {expr} parts but after processing the text there’s a different number of {} placeholders. Make the counts match.

Current limitations

• Best with one-line snippets. Line breaks inside content may not parse.
• Case-sensitive tag names.
• Interpolated expressions must implement Display.

Todo ideas

• Icons collections
• Styles and style sheets
• Layouts
• Template syntax highlighting in code editors
• Multi-line code snippets
• Event Handling Attributes
• Fonts and text style
• Documentation on docs.rs
• New tags: Heading, Hyperlink, Image, Table, Tabs

Recipes

Right-aligned dynamic status

ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
    let status = arbitrage_ui.arbitrage_status.to_string();
    efx!(ui, r#"<Label>Status: {status}</Label>"#);
});

Button with click handling

if efx!(ui, r#"<Button>Refresh quotes</Button>"#).clicked() {
    // trigger refresh
}

Braces + expression

let text = "test text";
efx!(ui, r#"<Label>Print {{ {text} }}</Label>"#);

Tag reference

• Label

  Syntax: <Label>Text with {expressions}</Label>

  Equivalent: ui.label(RichText::new(text))

  Returns: ()

• Button

  Syntax: <Button>Text with {expressions}</Button>

  Equivalent: ui.button(text)

  Returns: egui::Response

Changelog

See in file Changelog.md

Licence

The MIT License. Please see License File for more information.