agg_gui/widgets/
conditional.rs

1//! Conditional — show/hide a single child based on an external Cell<bool>.
2
3use std::cell::Cell;
4use std::rc::Rc;
5
6use crate::draw_ctx::DrawCtx;
7use crate::event::{Event, EventResult};
8use crate::geometry::{Rect, Size};
9use crate::layout_props::{HAnchor, Insets, VAnchor, WidgetBase};
10use crate::widget::Widget;
11
12/// Wrap a single child widget; show or hide it based on a shared boolean.
13///
14/// Mirrors the React-style `{cond && <Child/>}` pattern but without
15/// rebuilding the child on every toggle — the child keeps its state
16/// across show/hide cycles.  When hidden, layout returns `(0, 0)` and
17/// `is_visible` returns `false`, so paint / event dispatch skip the
18/// subtree.  Containers like `FlexColumn` honour `is_visible` to skip
19/// gap/margin allotted to hidden slots.
20pub struct Conditional {
21    bounds: Rect,
22    children: Vec<Box<dyn Widget>>, // 0 or 1 element
23    base: WidgetBase,
24    visible: Rc<Cell<bool>>,
25}
26
27impl Conditional {
28    pub fn new(visible: Rc<Cell<bool>>, child: Box<dyn Widget>) -> Self {
29        Self {
30            bounds: Rect::default(),
31            children: vec![child],
32            base: WidgetBase::new(),
33            visible,
34        }
35    }
36
37    pub fn visibility_cell(&self) -> Rc<Cell<bool>> {
38        Rc::clone(&self.visible)
39    }
40}
41
42impl Widget for Conditional {
43    fn type_name(&self) -> &'static str {
44        "Conditional"
45    }
46    fn bounds(&self) -> Rect {
47        self.bounds
48    }
49    fn set_bounds(&mut self, b: Rect) {
50        self.bounds = b;
51    }
52    fn children(&self) -> &[Box<dyn Widget>] {
53        &self.children
54    }
55    fn children_mut(&mut self) -> &mut Vec<Box<dyn Widget>> {
56        &mut self.children
57    }
58
59    fn margin(&self) -> Insets {
60        self.base.margin
61    }
62    fn widget_base(&self) -> Option<&WidgetBase> {
63        Some(&self.base)
64    }
65    fn widget_base_mut(&mut self) -> Option<&mut WidgetBase> {
66        Some(&mut self.base)
67    }
68    fn h_anchor(&self) -> HAnchor {
69        self.base.h_anchor
70    }
71    fn v_anchor(&self) -> VAnchor {
72        self.base.v_anchor
73    }
74
75    fn layout(&mut self, available: Size) -> Size {
76        if !self.visible.get() {
77            self.bounds = Rect::new(0.0, 0.0, 0.0, 0.0);
78            return Size::new(0.0, 0.0);
79        }
80        if let Some(child) = self.children.first_mut() {
81            let s = child.layout(available);
82            child.set_bounds(Rect::new(0.0, 0.0, s.width, s.height));
83            self.bounds = Rect::new(0.0, 0.0, s.width, s.height);
84            return s;
85        }
86        Size::new(0.0, 0.0)
87    }
88
89    fn paint(&mut self, _ctx: &mut dyn DrawCtx) {}
90
91    fn is_visible(&self) -> bool {
92        self.visible.get()
93    }
94
95    fn on_event(&mut self, _e: &Event) -> EventResult {
96        EventResult::Ignored
97    }
98}
agg_gui/widgets/conditional.rs

agg_gui/widgets/
conditional.rs
