1use std::ops::DerefMut;
2
3use crate::{
4 geometry::{rect::RectF, vector::Vector2F},
5 platform::CursorStyle,
6 CursorStyleHandle, DebugContext, Element, ElementBox, ElementStateHandle, ElementStateId,
7 Event, EventContext, LayoutContext, MutableAppContext, PaintContext, SizeConstraint,
8};
9use serde_json::json;
10
11pub struct MouseEventHandler {
12 state: ElementStateHandle<MouseState>,
13 child: ElementBox,
14 cursor_style: Option<CursorStyle>,
15 mouse_down_handler: Option<Box<dyn FnMut(&mut EventContext)>>,
16 click_handler: Option<Box<dyn FnMut(&mut EventContext)>>,
17 drag_handler: Option<Box<dyn FnMut(Vector2F, &mut EventContext)>>,
18}
19
20#[derive(Default)]
21pub struct MouseState {
22 pub hovered: bool,
23 pub clicked: bool,
24 prev_drag_position: Option<Vector2F>,
25 cursor_style_handle: Option<CursorStyleHandle>,
26}
27
28impl MouseEventHandler {
29 pub fn new<Tag, F, C, Id>(id: Id, cx: &mut C, render_child: F) -> Self
30 where
31 Tag: 'static,
32 F: FnOnce(&MouseState, &mut C) -> ElementBox,
33 C: DerefMut<Target = MutableAppContext>,
34 Id: Into<ElementStateId>,
35 {
36 let state_handle = cx.element_state::<Tag, _>(id.into());
37 let child = state_handle.update(cx, |state, cx| render_child(state, cx));
38 Self {
39 state: state_handle,
40 child,
41 cursor_style: None,
42 mouse_down_handler: None,
43 click_handler: None,
44 drag_handler: None,
45 }
46 }
47
48 pub fn with_cursor_style(mut self, cursor: CursorStyle) -> Self {
49 self.cursor_style = Some(cursor);
50 self
51 }
52
53 pub fn on_mouse_down(mut self, handler: impl FnMut(&mut EventContext) + 'static) -> Self {
54 self.mouse_down_handler = Some(Box::new(handler));
55 self
56 }
57
58 pub fn on_click(mut self, handler: impl FnMut(&mut EventContext) + 'static) -> Self {
59 self.click_handler = Some(Box::new(handler));
60 self
61 }
62
63 pub fn on_drag(mut self, handler: impl FnMut(Vector2F, &mut EventContext) + 'static) -> Self {
64 self.drag_handler = Some(Box::new(handler));
65 self
66 }
67}
68
69impl Element for MouseEventHandler {
70 type LayoutState = ();
71 type PaintState = ();
72
73 fn layout(
74 &mut self,
75 constraint: SizeConstraint,
76 cx: &mut LayoutContext,
77 ) -> (Vector2F, Self::LayoutState) {
78 (self.child.layout(constraint, cx), ())
79 }
80
81 fn paint(
82 &mut self,
83 bounds: RectF,
84 _: &mut Self::LayoutState,
85 cx: &mut PaintContext,
86 ) -> Self::PaintState {
87 self.child.paint(bounds.origin(), cx);
88 }
89
90 fn dispatch_event(
91 &mut self,
92 event: &Event,
93 bounds: RectF,
94 _: &mut Self::LayoutState,
95 _: &mut Self::PaintState,
96 cx: &mut EventContext,
97 ) -> bool {
98 let cursor_style = self.cursor_style;
99 let mouse_down_handler = self.mouse_down_handler.as_mut();
100 let click_handler = self.click_handler.as_mut();
101 let drag_handler = self.drag_handler.as_mut();
102
103 let handled_in_child = self.child.dispatch_event(event, cx);
104
105 self.state.update(cx, |state, cx| match event {
106 Event::MouseMoved {
107 position,
108 left_mouse_down,
109 } => {
110 if !left_mouse_down {
111 let mouse_in = bounds.contains_point(*position);
112 if state.hovered != mouse_in {
113 state.hovered = mouse_in;
114 if let Some(cursor_style) = cursor_style {
115 if !state.clicked {
116 if state.hovered {
117 state.cursor_style_handle =
118 Some(cx.set_cursor_style(cursor_style));
119 } else {
120 state.cursor_style_handle = None;
121 }
122 }
123 }
124 cx.notify();
125 return true;
126 }
127 }
128 handled_in_child
129 }
130 Event::LeftMouseDown { position, .. } => {
131 if !handled_in_child && bounds.contains_point(*position) {
132 state.clicked = true;
133 state.prev_drag_position = Some(*position);
134 cx.notify();
135 if let Some(handler) = mouse_down_handler {
136 handler(cx);
137 }
138 true
139 } else {
140 handled_in_child
141 }
142 }
143 Event::LeftMouseUp { position, .. } => {
144 state.prev_drag_position = None;
145 if !handled_in_child && state.clicked {
146 state.clicked = false;
147 if !state.hovered {
148 state.cursor_style_handle = None;
149 }
150 cx.notify();
151 if let Some(handler) = click_handler {
152 if bounds.contains_point(*position) {
153 handler(cx);
154 }
155 }
156 true
157 } else {
158 handled_in_child
159 }
160 }
161 Event::LeftMouseDragged { position, .. } => {
162 if !handled_in_child && state.clicked {
163 let prev_drag_position = state.prev_drag_position.replace(*position);
164 if let Some((handler, prev_position)) = drag_handler.zip(prev_drag_position) {
165 let delta = *position - prev_position;
166 if !delta.is_zero() {
167 (handler)(delta, cx);
168 }
169 }
170 true
171 } else {
172 handled_in_child
173 }
174 }
175 _ => handled_in_child,
176 })
177 }
178
179 fn debug(
180 &self,
181 _: RectF,
182 _: &Self::LayoutState,
183 _: &Self::PaintState,
184 cx: &DebugContext,
185 ) -> serde_json::Value {
186 json!({
187 "type": "MouseEventHandler",
188 "child": self.child.debug(cx),
189 })
190 }
191}