iced_core/
widget.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
//! Create custom widgets and operate on them.
pub mod operation;
pub mod text;
pub mod tree;

mod id;

pub use id::Id;
pub use operation::Operation;
pub use text::Text;
pub use tree::Tree;

use crate::layout::{self, Layout};
use crate::mouse;
use crate::overlay;
use crate::renderer;
use crate::{Clipboard, Event, Length, Rectangle, Shell, Size, Vector};

/// A component that displays information and allows interaction.
///
/// If you want to build your own widgets, you will need to implement this
/// trait.
///
/// # Examples
/// The repository has some [examples] showcasing how to implement a custom
/// widget:
///
/// - [`bezier_tool`], a Paint-like tool for drawing Bézier curves using
///   [`lyon`].
/// - [`custom_widget`], a demonstration of how to build a custom widget that
///   draws a circle.
/// - [`geometry`], a custom widget showcasing how to draw geometry with the
///   `Mesh2D` primitive in [`iced_wgpu`].
///
/// [examples]: https://github.com/iced-rs/iced/tree/0.13/examples
/// [`bezier_tool`]: https://github.com/iced-rs/iced/tree/0.13/examples/bezier_tool
/// [`custom_widget`]: https://github.com/iced-rs/iced/tree/0.13/examples/custom_widget
/// [`geometry`]: https://github.com/iced-rs/iced/tree/0.13/examples/geometry
/// [`lyon`]: https://github.com/nical/lyon
/// [`iced_wgpu`]: https://github.com/iced-rs/iced/tree/0.13/wgpu
pub trait Widget<Message, Theme, Renderer>
where
    Renderer: crate::Renderer,
{
    /// Returns the [`Size`] of the [`Widget`] in lengths.
    fn size(&self) -> Size<Length>;

    /// Returns a [`Size`] hint for laying out the [`Widget`].
    ///
    /// This hint may be used by some widget containers to adjust their sizing strategy
    /// during construction.
    fn size_hint(&self) -> Size<Length> {
        self.size()
    }

    /// Returns the [`layout::Node`] of the [`Widget`].
    ///
    /// This [`layout::Node`] is used by the runtime to compute the [`Layout`] of the
    /// user interface.
    fn layout(
        &self,
        tree: &mut Tree,
        renderer: &Renderer,
        limits: &layout::Limits,
    ) -> layout::Node;

    /// Draws the [`Widget`] using the associated `Renderer`.
    fn draw(
        &self,
        tree: &Tree,
        renderer: &mut Renderer,
        theme: &Theme,
        style: &renderer::Style,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        viewport: &Rectangle,
    );

    /// Returns the [`Tag`] of the [`Widget`].
    ///
    /// [`Tag`]: tree::Tag
    fn tag(&self) -> tree::Tag {
        tree::Tag::stateless()
    }

    /// Returns the [`State`] of the [`Widget`].
    ///
    /// [`State`]: tree::State
    fn state(&self) -> tree::State {
        tree::State::None
    }

    /// Returns the state [`Tree`] of the children of the [`Widget`].
    fn children(&self) -> Vec<Tree> {
        Vec::new()
    }

    /// Reconciles the [`Widget`] with the provided [`Tree`].
    fn diff(&self, _tree: &mut Tree) {}

    /// Applies an [`Operation`] to the [`Widget`].
    fn operate(
        &self,
        _state: &mut Tree,
        _layout: Layout<'_>,
        _renderer: &Renderer,
        _operation: &mut dyn Operation,
    ) {
    }

    /// Processes a runtime [`Event`].
    ///
    /// By default, it does nothing.
    fn update(
        &mut self,
        _state: &mut Tree,
        _event: Event,
        _layout: Layout<'_>,
        _cursor: mouse::Cursor,
        _renderer: &Renderer,
        _clipboard: &mut dyn Clipboard,
        _shell: &mut Shell<'_, Message>,
        _viewport: &Rectangle,
    ) {
    }

    /// Returns the current [`mouse::Interaction`] of the [`Widget`].
    ///
    /// By default, it returns [`mouse::Interaction::Idle`].
    fn mouse_interaction(
        &self,
        _state: &Tree,
        _layout: Layout<'_>,
        _cursor: mouse::Cursor,
        _viewport: &Rectangle,
        _renderer: &Renderer,
    ) -> mouse::Interaction {
        mouse::Interaction::None
    }

    /// Returns the overlay of the [`Widget`], if there is any.
    fn overlay<'a>(
        &'a mut self,
        _state: &'a mut Tree,
        _layout: Layout<'_>,
        _renderer: &Renderer,
        _translation: Vector,
    ) -> Option<overlay::Element<'a, Message, Theme, Renderer>> {
        None
    }
}