egui/emigui/src/memory.rs

use std::collections::HashMap;

use crate::{
    containers::{collapsing_header, floating, resize, scroll_area},
    Id, Layer, Pos2, Rect,
};

#[derive(Clone, Debug, Default)]
pub struct Memory {
    /// The widget being interacted with (e.g. dragged, in case of a slider).
    pub(crate) active_id: Option<Id>,

    /// The widget with keyboard focus (i.e. a text input field).
    pub(crate) kb_focus_id: Option<Id>,

    // states of various types of widgets
    pub(crate) collapsing_headers: HashMap<Id, collapsing_header::State>,
    pub(crate) scroll_areas: HashMap<Id, scroll_area::State>,
    pub(crate) resize: HashMap<Id, resize::State>,
    floating: HashMap<Id, floating::State>,

    /// Top is last
    pub floating_order: Vec<Id>,
}

impl Memory {
    pub fn get_floating(&mut self, id: Id) -> Option<floating::State> {
        self.floating.get(&id).cloned()
    }

    pub fn set_floating_state(&mut self, id: Id, state: floating::State) {
        let did_insert = self.floating.insert(id, state).is_none();
        if did_insert {
            self.floating_order.push(id);
        }
    }

    /// TODO: call once at the start of the frame for the current mouse pos
    pub fn layer_at(&self, pos: Pos2) -> Layer {
        for floating_id in self.floating_order.iter().rev() {
            if let Some(state) = self.floating.get(floating_id) {
                let rect = Rect::from_min_size(state.pos, state.size);
                if rect.contains(pos) {
                    return Layer::Window(*floating_id);
                }
            }
        }
        Layer::Background
    }

    pub fn move_floating_to_top(&mut self, id: Id) {
        if self.floating_order.last() == Some(&id) {
            return; // common case early-out
        }
        if let Some(index) = self.floating_order.iter().position(|x| *x == id) {
            self.floating_order.remove(index);
        }
        self.floating_order.push(id);
    }
}