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103 lines
3.3 KiB
Rust
103 lines
3.3 KiB
Rust
//! element API, built-in elements like `Container`, `Button`, `Text`, etc.
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use std::any::Any;
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use crate::{
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draw::UiDrawCommandList,
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layout::LayoutInfo,
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measure::Response,
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state::StateRepo,
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text::{FontHandle, TextMeasure},
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UiInstance
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};
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mod builtin;
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pub use builtin::*;
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/// Context for the `Element::measure` function
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pub struct MeasureContext<'a> {
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pub state: &'a StateRepo,
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pub layout: &'a LayoutInfo,
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pub text_measure: TextMeasure<'a>,
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pub current_font: FontHandle,
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}
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/// Context for the `Element::process` function
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pub struct ProcessContext<'a> {
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pub measure: &'a Response,
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pub state: &'a mut StateRepo,
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pub layout: &'a LayoutInfo,
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pub draw: &'a mut UiDrawCommandList,
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pub text_measure: TextMeasure<'a>,
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pub current_font: FontHandle,
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}
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pub trait UiElement {
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/// Get the name of the element, for example "Button" or "ProgressBar"
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fn name(&self) -> &'static str { "UiElement" }
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/// Get the unique id used for internal state management\
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/// This value must be unique for each instance of the element
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///
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/// If the element is stateless, this function should return `None`
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fn state_id(&self) -> Option<u64> { None }
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/// Check if the element has state
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fn is_stateful(&self) -> bool { self.state_id().is_some() }
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/// Check if the element has no state
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fn is_stateless(&self) -> bool { self.state_id().is_none() }
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/// Initialize the state of the element\
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/// This function should be called exactly once during the lifetime of the element,
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/// or if the state gets reset
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///
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/// This function will not get called for stateless elements
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fn init_state(&self) -> Option<Box<dyn Any>> { None }
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/// Measure step, guaranteed to be called before the `process` step\
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/// May be called multiple times per single frame, so it should not contain any expensive calls\
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/// This function may not mutate any state.\
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///
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/// This function should return the size of the element along with any hints or layout metadata
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fn measure(&self, ctx: MeasureContext) -> Response;
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/// Process step, guaranteed to be called after the `measure` step\
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/// You should process the user inputs and render the element here.
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fn process(&self, ctx: ProcessContext);
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}
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/// A list of elements\
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/// Use the [`add`](`ElementList::add`) method to add elements to the list
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pub struct ElementList(pub Vec<Box<dyn UiElement>>);
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impl ElementList {
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/// Add an element to the list
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pub fn add(&mut self, element: impl UiElement + 'static) {
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self.0.push(Box::new(element))
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}
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/// Create a new `ElementList` from a callback\
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/// The callback will be called with a reference to the newly list
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pub(crate) fn from_callback(cb: impl FnOnce(&mut ElementList)) -> Self {
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let mut list = ElementList(Vec::new());
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cb(&mut list);
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list
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}
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}
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pub trait UiElementExt: UiElement {
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/// Add element as a child/nested element.
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fn add_child(self, ui: &mut ElementList);
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/// Add element as a ui root.
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fn add_root(self, ui: &mut UiInstance, max_size: glam::Vec2);
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}
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impl<T: UiElement + 'static> UiElementExt for T {
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fn add_child(self, ui: &mut ElementList) {
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ui.add(self)
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}
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fn add_root(self, ui: &mut UiInstance, max_size: glam::Vec2) {
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ui.add(self, max_size);
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}
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}
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