1use crate::{
  2    geometry::{rect::RectF, vector::Vector2F},
  3    AppContext, DebugContext, Element, ElementBox, Event, EventContext, LayoutContext,
  4    PaintContext, SizeConstraint, ValueHandle,
  5};
  6use serde_json::json;
  7
  8pub struct MouseEventHandler {
  9    state: ValueHandle<MouseState>,
 10    child: ElementBox,
 11    click_handler: Option<Box<dyn FnMut(&mut EventContext)>>,
 12}
 13
 14#[derive(Clone, Copy, Debug, Default)]
 15pub struct MouseState {
 16    pub hovered: bool,
 17    pub clicked: bool,
 18}
 19
 20impl MouseEventHandler {
 21    pub fn new<Tag, F>(id: usize, cx: &AppContext, render_child: F) -> Self
 22    where
 23        Tag: 'static,
 24        F: FnOnce(MouseState) -> ElementBox,
 25    {
 26        let state_handle = cx.value::<Tag, _>(id);
 27        let state = state_handle.read(cx.as_ref(), |state| *state);
 28        let child = render_child(state);
 29        Self {
 30            state: state_handle,
 31            child,
 32            click_handler: None,
 33        }
 34    }
 35
 36    pub fn on_click(mut self, handler: impl FnMut(&mut EventContext) + 'static) -> Self {
 37        self.click_handler = Some(Box::new(handler));
 38        self
 39    }
 40}
 41
 42impl Element for MouseEventHandler {
 43    type LayoutState = ();
 44    type PaintState = ();
 45
 46    fn layout(
 47        &mut self,
 48        constraint: SizeConstraint,
 49        cx: &mut LayoutContext,
 50    ) -> (Vector2F, Self::LayoutState) {
 51        (self.child.layout(constraint, cx), ())
 52    }
 53
 54    fn paint(
 55        &mut self,
 56        bounds: RectF,
 57        _: &mut Self::LayoutState,
 58        cx: &mut PaintContext,
 59    ) -> Self::PaintState {
 60        self.child.paint(bounds.origin(), cx);
 61    }
 62
 63    fn dispatch_event(
 64        &mut self,
 65        event: &Event,
 66        bounds: RectF,
 67        _: &mut Self::LayoutState,
 68        _: &mut Self::PaintState,
 69        cx: &mut EventContext,
 70    ) -> bool {
 71        let click_handler = self.click_handler.as_mut();
 72
 73        let handled_in_child = self.child.dispatch_event(event, cx);
 74
 75        self.state.update(cx, |state, cx| match event {
 76            Event::MouseMoved { position } => {
 77                let mouse_in = bounds.contains_point(*position);
 78                if state.hovered != mouse_in {
 79                    state.hovered = mouse_in;
 80                    cx.notify();
 81                    true
 82                } else {
 83                    handled_in_child
 84                }
 85            }
 86            Event::LeftMouseDown { position, .. } => {
 87                if !handled_in_child && bounds.contains_point(*position) {
 88                    state.clicked = true;
 89                    cx.notify();
 90                    true
 91                } else {
 92                    handled_in_child
 93                }
 94            }
 95            Event::LeftMouseUp { position, .. } => {
 96                if !handled_in_child && state.clicked {
 97                    state.clicked = false;
 98                    cx.notify();
 99                    if let Some(handler) = click_handler {
100                        if bounds.contains_point(*position) {
101                            handler(cx);
102                        }
103                    }
104                    true
105                } else {
106                    handled_in_child
107                }
108            }
109            _ => handled_in_child,
110        })
111    }
112
113    fn debug(
114        &self,
115        _: RectF,
116        _: &Self::LayoutState,
117        _: &Self::PaintState,
118        cx: &DebugContext,
119    ) -> serde_json::Value {
120        json!({
121            "type": "MouseEventHandler",
122            "child": self.child.debug(cx),
123        })
124    }
125}