floem-css

Hot reloading css-like styles for Floem

floem-css at least tries to support all currently supported style properties that Floem supports. Supported properties can be found from src/style/parser.rs and examining enum StyleParser variants.

This library is experimental and made for personal usage, some features are lacking, and it may have lots of breaking changes in future

Usage

style.css

body {
    flex-grow: 1;
}

my-header {
    font-size: 32px;
    font-weight: 600;
}

main.rs

use floem::views::{container, text};
use floem::IntoView;
use floem_css::{theme_provider, ProviderOptions, StyleCss};

fn main() {
    // Styles are read from this path.
    // Modify the css file to instantly see changes in app.
    // Path can point to file or folder.
    let options = ProviderOptions {
        path: "./style.css".into(),
        ..Default::default()
    };

    // Wrap your app in theme_provider and launch
    floem::launch(|| theme_provider(main_view, options))
}

fn main_view() -> impl IntoView {
    let my_text = text("Change my style").css("my-header");
    container(my_text).css("body")
}

This example shows to use this library. Now just run the app with cargo run and edit your css file to see the changes immediately on the app. There is also larger example available, see examples section below.

Differences to normal css

Simple Selectors

Selectors don't have . or # prefixes for classes, unless you decide to do so manually. So rust code button("click").css("button"), matches with css selector button, not .button like you would expect with normal css.

No combinators

There is no support for combinators. Defining descendant, child or sibling combinators is not supported. In example normally you would define styles for specific descendants like this:

Rust:

let home = button("home").css("button");
let about = button("home").css("button");
let navigation = v_stack((home, about)).css("navigation");

Css:

button { ... } // Applies to all elements with class "button"
navigation button { ... } // Applies to all buttons that are descendants of navigation

But that will not work as expected. You have to define specific rule:

Rust:

let home = button("home").css("button nav-button");
let about = button("home").css("button nav-button");
let navigation = v_stack((home, about)).css("navigation");

Css:

button { ... } // Applies to all elements with class "button"
nav-button { ... } // Applies to all elements with class "nav-button"

To make this easier and your code less cluttered, it's recommended to create wrapper function for elements that are used often:

fn my_button<V: IntoView + 'static>(child: V) -> Button {
    button(child).css("button")
}

fn nav_button<V: IntoView + 'static>(child: V) -> Button {
    my_button(child).css("nav-button")
}

let home = nav_button("home");
let about = nav_button("about");
let navigation = v_stack((home, about)).css("navigation");

Examples

Run example with:

cargo run --example provider

And modify examples/style.css to update the apps style instantly.

Building

When building or running with --release flag, you must specify environment variable STYLE_PATH that points to file or folder where your style(s) are located. Styles are then compiled in the app build-time and responsive updates no longer work.

Building example (bash):

STYLE_PATH=$(pwd)/examples/style.css cargo build --example provider --release

Or to make it easier set variable for project .cargo/config.toml:

[env]
STYLE_PATH = "/path/to/my/style.css"