Trait eframe::App

pub trait App {
    // Required method
    fn update(&mut self, ctx: &Context, frame: &mut Frame);

    // Provided methods
    fn as_any_mut(&mut self) -> Option<&mut dyn Any> { ... }
    fn save(&mut self, _storage: &mut dyn Storage) { ... }
    fn on_exit(&mut self, _gl: Option<&Context>) { ... }
    fn auto_save_interval(&self) -> Duration { ... }
    fn clear_color(&self, _visuals: &Visuals) -> [f32; 4] { ... }
    fn persist_egui_memory(&self) -> bool { ... }
}

Implement this trait to write apps that can be compiled for both web/wasm and desktop/native using eframe.

Required Methods

fn update(&mut self, ctx: &Context, frame: &mut Frame)

Called each time the UI needs repainting, which may be many times per second.

Put your widgets into a egui::SidePanel, egui::TopBottomPanel, egui::CentralPanel, egui::Window or egui::Area.

The egui::Context can be cloned and saved if you like.

To force a repaint, call egui::Context::request_repaint at any time (e.g. from another thread).

This is called for the root viewport (egui::ViewportId::ROOT). Use egui::Context::show_viewport_deferred to spawn additional viewports (windows). (A “viewport” in egui means an native OS window).

Provided Methods

fn as_any_mut(&mut self) -> Option<&mut dyn Any>

Get a handle to the app.

Can be used from web to interact or other external context.

You need to implement this if you want to be able to access the application from JS using crate::WebRunner::app_mut.

This is needed because downcasting Box<dyn App> -> Box<dyn Any> to get &ConcreteApp is not simple in current rust.

Just copy-paste this as your implementation:

#[cfg(target_arch = "wasm32")]
fn as_any_mut(&mut self) -> Option<&mut dyn std::any::Any> {
    Some(&mut *self)
}

fn save(&mut self, _storage: &mut dyn Storage)

Called on shutdown, and perhaps at regular intervals. Allows you to save state.

Only called when the “persistence” feature is enabled.

On web the state is stored to “Local Storage”.

On native the path is picked using [crate::storage_dir].

fn on_exit(&mut self, _gl: Option<&Context>)

Called once on shutdown, after Self::save.

If you need to abort an exit check ctx.input(|i| i.viewport().close_requested()) and respond with egui::ViewportCommand::CancelClose.

To get a glow context you need to compile with the glow feature flag, and run eframe with the glow backend.

fn auto_save_interval(&self) -> Duration

Time between automatic calls to Self::save

fn clear_color(&self, _visuals: &Visuals) -> [f32; 4]

Background color values for the app, e.g. what is sent to gl.clearColor.

This is the background of your windows if you don’t set a central panel.

ATTENTION: Since these float values go to the render as-is, any color space conversion as done e.g. by converting from [egui::Color32] to [egui::Rgba] may cause incorrect results. egui recommends that rendering backends use a normal “gamma-space” (non-sRGB-aware) blending, which means the values you return here should also be in sRGB gamma-space in the 0-1 range. You can use [egui::Color32::to_normalized_gamma_f32] for this.

fn persist_egui_memory(&self) -> bool

Controls whether or not the egui memory (window positions etc) will be persisted (only if the “persistence” feature is enabled).

Implementors