fission_core/ui/widgets/
overlay.rs

1use crate::lowering::{LoweringContext, NodeBuilder, wrap_zstack_child};
2use crate::ui::traits::Lower;
3use crate::ui::{Node, Text, TextContent};
4use fission_ir::{LayoutOp, NodeId, Op};
5use serde::{Deserialize, Serialize};
6
7/// A widget that renders an overlay layer on top of its content.
8///
9/// The `content` is drawn first, then `overlay` is drawn on top, filling the
10/// same bounds via a [`ZStack`](super::ZStack) internally.
11///
12/// # Example
13///
14/// ```rust,ignore
15/// Overlay {
16///     content: Box::new(main_content),
17///     overlay: Box::new(loading_spinner),
18///     ..Default::default()
19/// }
20/// ```
21#[derive(Debug, Clone, Serialize, Deserialize)]
22pub struct Overlay {
23    /// Explicit node identity.
24    pub id: Option<NodeId>,
25    /// The primary content (drawn first / underneath).
26    pub content: Box<Node>,
27    /// The overlay content (drawn second / on top).
28    pub overlay: Box<Node>,
29}
30
31impl Overlay {
32    pub fn into_node(self) -> Node {
33        Node::Overlay(self)
34    }
35}
36
37impl Default for Overlay {
38    fn default() -> Self {
39        Self {
40            id: None,
41            content: Box::new(Node::Text(Text {
42                content: TextContent::Literal("".into()),
43                ..Default::default()
44            })),
45            overlay: Box::new(Node::Text(Text {
46                content: TextContent::Literal("".into()),
47                ..Default::default()
48            })),
49        }
50    }
51}
52
53impl Lower for Overlay {
54    fn lower(&self, cx: &mut LoweringContext) -> NodeId {
55        let id = self.id.unwrap_or_else(|| cx.next_node_id());
56        
57        cx.push_scope(id);
58
59        // Build overlay child in its own scope to avoid ID collisions
60        // with the content tree.
61        let overlay_scope = cx.next_node_id();
62        cx.push_scope(overlay_scope);
63        let overlay_child_id = self.overlay.lower(cx);
64        cx.pop_scope();
65        let mut overlay_fill =
66            NodeBuilder::new(cx.next_node_id(), Op::Layout(LayoutOp::AbsoluteFill));
67        overlay_fill.add_child(overlay_child_id);
68        let overlay_fill_id = overlay_fill.build(cx);
69
70        // Stack container: content first, overlay second.
71        let stack_id = cx.next_node_id();
72        let content_id = self.content.lower(cx);
73        cx.push_scope(stack_id);
74        let content_wrapped = wrap_zstack_child(cx, content_id);
75        let overlay_wrapped = wrap_zstack_child(cx, overlay_fill_id);
76        cx.pop_scope();
77
78        let mut stack = NodeBuilder::new(stack_id, Op::Layout(LayoutOp::ZStack));
79        stack.add_child(content_wrapped);
80        stack.add_child(overlay_wrapped);
81        let stack_id = stack.build(cx);
82
83        // Ensure the stack fills available space so overlay AbsoluteFill can cover
84        // the full viewport even when content is small.
85        let mut stack_wrapper = NodeBuilder::new(
86            cx.next_node_id(),
87            Op::Layout(LayoutOp::Box {
88                width: None,
89                height: None,
90                min_width: None,
91                max_width: None,
92                min_height: None,
93                max_height: None,
94                padding: [0.0; 4],
95                flex_grow: 1.0,
96                flex_shrink: 1.0,
97                aspect_ratio: None,
98            }),
99        );
100        stack_wrapper.add_child(stack_id);
101        let stack_wrapper_id = stack_wrapper.build(cx);
102
103        // Wrap ZStack in a Flex container with flex_grow = 1.0
104        // Flex defaults to stretching children, unlike Box which centers.
105        let mut root = NodeBuilder::new(
106            id, 
107            Op::Layout(LayoutOp::Flex {
108                direction: fission_ir::FlexDirection::Column,
109                wrap: fission_ir::FlexWrap::NoWrap,
110                flex_grow: 1.0,
111                flex_shrink: 1.0,
112                padding: [0.0; 4],
113                gap: None,
114                align_items: fission_ir::op::AlignItems::Stretch,
115                justify_content: fission_ir::op::JustifyContent::Start,
116            })
117        );
118        root.add_child(stack_wrapper_id);
119        
120        cx.pop_scope();
121        
122        root.build(cx)
123    }
124}
fission_core/ui/widgets/overlay.rs

fission_core/ui/widgets/
overlay.rs
