Core Concepts
Core Widget Traits
WidgetNode Trait
1pub trait WidgetNode: LiveApply {
2 // Main methods
3 fn uid_to_widget(&self, uid: WidgetUid) -> WidgetRef;
4 fn find_widgets(&self, path: &[LiveId], cached: WidgetCache, results: &mut WidgetSet);
5 fn walk(&mut self, cx: &mut Cx) -> Walk;
6 fn area(&self) -> Area;
7 fn redraw(&mut self, cx: &mut Cx);
8 // Other default implementations
9}
This is the foundational trait for all Widgets:
- Find Widget based on UID
- Find Widgets based on path
- Calculate layout position and size
- Manage drawing areas
- Trigger redraws
Widget Trait
1pub type DrawStep = Result<(), WidgetRef>;
2
3pub trait Widget: WidgetNode {
4 fn handle_event(&mut self, cx: &mut Cx, event: &Event, scope: &mut Scope);
5 fn draw_walk(&mut self, cx: &mut Cx2d, scope: &mut Scope, walk: Walk) -> DrawStep;
6
7 // Other default implementations
8}
This trait extends WidgetNode, adding:
- Event handling system
- Drawing process control
Widget References and Management
WidgetRef
WidgetRef is a smart pointer wrapper for Widgets.
1pub struct WidgetRefInner {
2 pub widget: Box<dyn Widget>,
3}
4
5pub struct WidgetRef(Rc<RefCell<Option<WidgetRefInner>>>);
6
7// Key methods
8impl WidgetRef {
9 // Other methods
10 // Event handling
11 pub fn handle_event(&self, cx: &mut Cx, event: &Event, scope: &mut Scope) {
12 // ...
13 }
14
15 // Drawing
16 pub fn draw(&mut self, cx: &mut Cx2d, scope: &mut Scope) -> DrawStep {
17 // ...
18 }
19
20 // Get mutable reference to underlying Widget
21 pub fn borrow_mut<T: 'static + Widget>(&self) -> Option<RefMut<'_, T>> {
22 // ...
23 }
24
25 // Basic find method
26 pub fn find_widgets(&self, path: &[LiveId], cached: WidgetCache, results: &mut WidgetSet) {
27 if let Some(inner) = self.0.borrow().as_ref() {
28 inner.widget.find_widgets(path, cached, results)
29 }
30 }
31}
- Uses
Rc<RefCell> to provide reference counting and interior mutability
- Supports
Clone and thread safety
- Safe Widget access through
borrow/borrow_mut
WidgetCache
WidgetCache is an important performance optimization mechanism in the Makepad UI framework. It's a parameter that traverses the entire component tree, controlling whether components enable, clear, or bypass caching at each layer.
This is important for improving large UI performance because it can:
- Avoid repeated component tree traversal
- Force latest state retrieval when needed
- Clear invalid caches when component states change
1// Typical call chain:
2widget.widget(&path)
3 -> widget.find_widgets(path, WidgetCache::Yes) // High-level API defaults to using cache
4 -> child_widget.find_widgets(path, cached) // Continue passing cache parameter down
5 -> grandchild.find_widgets(path, cached) // Cache strategy needs to be consistent
WidgetSet
WidgetSet is a collection of WidgetRefs.
1pub struct WidgetSet(pub SmallVec<[WidgetRef;2]>);
- Efficiently manages multiple Widget references
- Supports batch operations and lookups
- Uses SmallVec to optimize memory usage in small-scale scenarios
