WrapperWidget, Space

src/context.rs

@@ -468,7 +468,17 @@ impl<'context, 'window, 'clip, 'gfx, 'pass> GraphicsContext<'context, 'window, '
 
     /// Invokes [`Widget::redraw()`](crate::widget::Widget::redraw) on this
     /// context's widget.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if the widget being drawn has no layout set (via
+    /// [`LayoutContext::set_child_layout()`]).
     pub fn redraw(&mut self) {
+        assert!(
+            self.last_layout().is_some(),
+            "redraw called without set_widget_layout"
+        );
+
         self.current_node
             .tree
             .note_widget_rendered(self.current_node.id());

src/value.rs

@@ -264,17 +264,7 @@ impl<T> DynamicData<T> {
             let mut changed = true;
             let result = map(&mut state.wrapped.value, &mut changed);
             if changed {
-                state.wrapped.generation = state.wrapped.generation.next();
-
-                for callback in &mut state.callbacks {
-                    callback.update(&state.wrapped);
-                }
-                for window in state.windows.drain(..) {
-                    window.redraw();
-                }
-                for waker in state.wakers.drain(..) {
-                    waker.wake();
-                }
+                state.note_changed();
             }
 
             result
@@ -321,6 +311,22 @@ struct State<T> {
     readers: usize,
 }
 
+impl<T> State<T> {
+    fn note_changed(&mut self) {
+        self.wrapped.generation = self.wrapped.generation.next();
+
+        for callback in &mut self.callbacks {
+            callback.update(&self.wrapped);
+        }
+        for window in self.windows.drain(..) {
+            window.redraw();
+        }
+        for waker in self.wakers.drain(..) {
+            waker.wake();
+        }
+    }
+}
+
 impl<T> Debug for State<T>
 where
     T: Debug,
@@ -353,6 +359,9 @@ struct GenerationalValue<T> {
 }
 
 /// An exclusive reference to the contents of a [`Dynamic`].
+///
+/// If the contents are accessed through [`DerefMut`], all obververs will be
+/// notified of a change when this guard is dropped.
 #[derive(Debug)]
 pub struct DynamicGuard<'a, T> {
     guard: MutexGuard<'a, State<T>>,
@@ -377,7 +386,7 @@ impl<'a, T> DerefMut for DynamicGuard<'a, T> {
 impl<T> Drop for DynamicGuard<'_, T> {
     fn drop(&mut self) {
         if self.accessed_mut {
-            todo!("trigger callbacks")
+            self.guard.note_changed();
         }
     }
 }

src/widget.rs

@@ -12,7 +12,7 @@ use kludgine::app::winit::event::{
     DeviceId, Ime, KeyEvent, MouseButton, MouseScrollDelta, TouchPhase,
 };
 use kludgine::figures::units::{Px, UPx};
-use kludgine::figures::{Point, Rect, Size};
+use kludgine::figures::{IntoSigned, IntoUnsigned, Point, Rect, Size};
 
 use crate::context::{AsEventContext, EventContext, GraphicsContext, LayoutContext};
 use crate::styles::components::VisualOrder;
@@ -167,6 +167,263 @@ where
     }
 }
 
+/// A [`Widget`] that contains a single child.
+pub trait WrapperWidget: Debug + Send + UnwindSafe + 'static {
+    /// Returns the child widget.
+    fn child(&mut self) -> &mut WidgetRef;
+
+    /// Returns the rectangle that the child widget should occupy given
+    /// `available_space`.
+    #[allow(unused_variables)]
+    fn layout_child(
+        &mut self,
+        available_space: Size<ConstraintLimit>,
+        context: &mut LayoutContext<'_, '_, '_, '_, '_>,
+    ) -> Rect<Px> {
+        let child = self.child().mounted(&mut context.as_event_context());
+
+        context
+            .for_other(&child)
+            .layout(available_space)
+            .into_signed()
+            .into()
+    }
+
+    /// The widget has been mounted into a parent widget.
+    #[allow(unused_variables)]
+    fn mounted(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// The widget has been removed from its parent widget.
+    #[allow(unused_variables)]
+    fn unmounted(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// Returns true if this widget should respond to mouse input at `location`.
+    #[allow(unused_variables)]
+    fn hit_test(&mut self, location: Point<Px>, context: &mut EventContext<'_, '_>) -> bool {
+        false
+    }
+
+    /// The widget is currently has a cursor hovering it at `location`.
+    #[allow(unused_variables)]
+    fn hover(&mut self, location: Point<Px>, context: &mut EventContext<'_, '_>) {}
+
+    /// The widget is no longer being hovered.
+    #[allow(unused_variables)]
+    fn unhover(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// This widget has been targeted to be focused. If this function returns
+    /// true, the widget will be focused. If false, Gooey will continue
+    /// searching for another focus target.
+    #[allow(unused_variables)]
+    fn accept_focus(&mut self, context: &mut EventContext<'_, '_>) -> bool {
+        false
+    }
+
+    /// The widget has received focus for user input.
+    #[allow(unused_variables)]
+    fn focus(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// The widget is no longer focused for user input.
+    #[allow(unused_variables)]
+    fn blur(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// The widget has become the active widget.
+    #[allow(unused_variables)]
+    fn activate(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// The widget is no longer active.
+    #[allow(unused_variables)]
+    fn deactivate(&mut self, context: &mut EventContext<'_, '_>) {}
+
+    /// A mouse button event has occurred at `location`. Returns whether the
+    /// event has been handled or not.
+    ///
+    /// If an event is handled, the widget will receive callbacks for
+    /// [`mouse_drag`](Self::mouse_drag) and [`mouse_up`](Self::mouse_up).
+    #[allow(unused_variables)]
+    fn mouse_down(
+        &mut self,
+        location: Point<Px>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        IGNORED
+    }
+
+    /// A mouse button is being held down as the cursor is moved across the
+    /// widget.
+    #[allow(unused_variables)]
+    fn mouse_drag(
+        &mut self,
+        location: Point<Px>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) {
+    }
+
+    /// A mouse button is no longer being pressed.
+    #[allow(unused_variables)]
+    fn mouse_up(
+        &mut self,
+        location: Option<Point<Px>>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) {
+    }
+
+    /// A keyboard event has been sent to this widget. Returns whether the event
+    /// has been handled or not.
+    #[allow(unused_variables)]
+    fn keyboard_input(
+        &mut self,
+        device_id: DeviceId,
+        input: KeyEvent,
+        is_synthetic: bool,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        IGNORED
+    }
+
+    /// An input manager event has been sent to this widget. Returns whether the
+    /// event has been handled or not.
+    #[allow(unused_variables)]
+    fn ime(&mut self, ime: Ime, context: &mut EventContext<'_, '_>) -> EventHandling {
+        IGNORED
+    }
+
+    /// A mouse wheel event has been sent to this widget. Returns whether the
+    /// event has been handled or not.
+    #[allow(unused_variables)]
+    fn mouse_wheel(
+        &mut self,
+        device_id: DeviceId,
+        delta: MouseScrollDelta,
+        phase: TouchPhase,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        IGNORED
+    }
+}
+
+impl<T> Widget for T
+where
+    T: WrapperWidget,
+{
+    fn redraw(&mut self, context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {
+        let child = self.child().mounted(&mut context.as_event_context());
+        context.for_other(&child).redraw();
+    }
+
+    fn layout(
+        &mut self,
+        available_space: Size<ConstraintLimit>,
+        context: &mut LayoutContext<'_, '_, '_, '_, '_>,
+    ) -> Size<UPx> {
+        let child = self.child().mounted(&mut context.as_event_context());
+
+        let layout = self.layout_child(available_space, context);
+        context.set_child_layout(&child, layout);
+        layout.size.into_unsigned()
+    }
+
+    fn mounted(&mut self, context: &mut EventContext<'_, '_>) {
+        T::mounted(self, context);
+    }
+
+    fn unmounted(&mut self, context: &mut EventContext<'_, '_>) {
+        T::unmounted(self, context);
+    }
+
+    fn hit_test(&mut self, location: Point<Px>, context: &mut EventContext<'_, '_>) -> bool {
+        T::hit_test(self, location, context)
+    }
+
+    fn hover(&mut self, location: Point<Px>, context: &mut EventContext<'_, '_>) {
+        T::hover(self, location, context);
+    }
+
+    fn unhover(&mut self, context: &mut EventContext<'_, '_>) {
+        T::unhover(self, context);
+    }
+
+    fn accept_focus(&mut self, context: &mut EventContext<'_, '_>) -> bool {
+        T::accept_focus(self, context)
+    }
+
+    fn focus(&mut self, context: &mut EventContext<'_, '_>) {
+        T::focus(self, context);
+    }
+
+    fn blur(&mut self, context: &mut EventContext<'_, '_>) {
+        T::blur(self, context);
+    }
+
+    fn activate(&mut self, context: &mut EventContext<'_, '_>) {
+        T::activate(self, context);
+    }
+
+    fn deactivate(&mut self, context: &mut EventContext<'_, '_>) {
+        T::deactivate(self, context);
+    }
+
+    fn mouse_down(
+        &mut self,
+        location: Point<Px>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        T::mouse_down(self, location, device_id, button, context)
+    }
+
+    fn mouse_drag(
+        &mut self,
+        location: Point<Px>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) {
+        T::mouse_drag(self, location, device_id, button, context);
+    }
+
+    fn mouse_up(
+        &mut self,
+        location: Option<Point<Px>>,
+        device_id: DeviceId,
+        button: MouseButton,
+        context: &mut EventContext<'_, '_>,
+    ) {
+        T::mouse_up(self, location, device_id, button, context);
+    }
+
+    fn keyboard_input(
+        &mut self,
+        device_id: DeviceId,
+        input: KeyEvent,
+        is_synthetic: bool,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        T::keyboard_input(self, device_id, input, is_synthetic, context)
+    }
+
+    fn ime(&mut self, ime: Ime, context: &mut EventContext<'_, '_>) -> EventHandling {
+        T::ime(self, ime, context)
+    }
+
+    fn mouse_wheel(
+        &mut self,
+        device_id: DeviceId,
+        delta: MouseScrollDelta,
+        phase: TouchPhase,
+        context: &mut EventContext<'_, '_>,
+    ) -> EventHandling {
+        T::mouse_wheel(self, device_id, delta, phase, context)
+    }
+}
+
 /// A type that can create a [`WidgetInstance`].
 pub trait MakeWidget: Sized {
     /// Returns a new widget.

src/widgets.rs

@@ -8,6 +8,7 @@ mod input;
 mod label;
 mod resize;
 pub mod scroll;
+mod space;
 pub mod stack;
 mod style;
 mod tilemap;
@@ -20,6 +21,7 @@ pub use input::Input;
 pub use label::Label;
 pub use resize::Resize;
 pub use scroll::Scroll;
+pub use space::Space;
 pub use stack::Stack;
 pub use style::Style;
 pub use tilemap::TileMap;

src/widgets/align.rs

@@ -3,10 +3,10 @@ use std::fmt::Debug;
 use kludgine::figures::units::UPx;
 use kludgine::figures::{Fraction, IntoSigned, IntoUnsigned, Point, Rect, ScreenScale, Size};
 
-use crate::context::{AsEventContext, GraphicsContext, LayoutContext};
+use crate::context::{AsEventContext, LayoutContext};
 use crate::styles::{Dimension, Edges, FlexibleDimension};
 use crate::value::{IntoValue, Value};
-use crate::widget::{MakeWidget, Widget, WidgetRef};
+use crate::widget::{MakeWidget, WidgetRef, WrapperWidget};
 use crate::ConstraintLimit;
 
 /// A widget aligns its contents to its container's boundaries.
@@ -145,31 +145,31 @@ impl FrameInfo {
     }
 }
 
-impl Widget for Align {
-    fn redraw(&mut self, context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {
-        let child = self.child.mounted(&mut context.as_event_context());
-        context.for_other(&child).redraw();
+impl WrapperWidget for Align {
+    fn child(&mut self) -> &mut WidgetRef {
+        &mut self.child
     }
 
-    fn layout(
+    fn layout_child(
         &mut self,
         available_space: Size<ConstraintLimit>,
         context: &mut LayoutContext<'_, '_, '_, '_, '_>,
-    ) -> Size<UPx> {
-        let child = self.child.mounted(&mut context.as_event_context());
+    ) -> Rect<kludgine::figures::units::Px> {
         let layout = self.measure(available_space, context);
-        context.set_child_layout(
-            &child,
-            Rect::new(
-                Point::new(
-                    layout.margin.left.into_signed(),
-                    layout.margin.top.into_signed(),
-                ),
-                layout.content.into_signed(),
-            ),
-        );
 
-        layout.size().into_unsigned()
+        Rect::new(
+            Point::new(
+                layout.margin.left.into_signed(),
+                layout.margin.top.into_signed(),
+            ),
+            layout.content.into_signed(),
+        )
+    }
+}
+
+impl AsMut<WidgetRef> for Align {
+    fn as_mut(&mut self) -> &mut WidgetRef {
+        &mut self.child
     }
 }
 
@@ -178,9 +178,3 @@ struct Layout {
     margin: Edges<UPx>,
     content: Size<UPx>,
 }
-
-impl Layout {
-    pub fn size(&self) -> Size<UPx> {
-        self.margin.size() + self.content
-    }
-}

src/widgets/expand.rs

@@ -1,8 +1,9 @@
-use kludgine::figures::units::UPx;
+use kludgine::figures::units::{Px, UPx};
 use kludgine::figures::{IntoSigned, Rect, Size};
 
-use crate::context::{AsEventContext, GraphicsContext, LayoutContext};
-use crate::widget::{MakeWidget, Widget, WidgetRef};
+use crate::context::{AsEventContext, LayoutContext};
+use crate::widget::{MakeWidget, WidgetRef, WrapperWidget};
+use crate::widgets::Space;
 use crate::ConstraintLimit;
 
 /// A widget that expands its child widget to fill the parent.
@@ -14,7 +15,7 @@ pub struct Expand {
     /// The weight to use when splitting available space with multiple
     /// [`Expand`] widgets.
     pub weight: u8,
-    child: Option<WidgetRef>,
+    child: WidgetRef,
 }
 
 impl Default for Expand {
@@ -28,7 +29,7 @@ impl Expand {
     #[must_use]
     pub fn new(child: impl MakeWidget) -> Self {
         Self {
-            child: Some(WidgetRef::new(child)),
+            child: WidgetRef::new(child),
             weight: 1,
         }
     }
@@ -37,7 +38,7 @@ impl Expand {
     #[must_use]
     pub fn empty() -> Self {
         Self {
-            child: None,
+            child: WidgetRef::new(Space),
             weight: 1,
         }
     }
@@ -49,57 +50,44 @@ impl Expand {
     #[must_use]
     pub fn weighted(weight: u8, child: impl MakeWidget) -> Self {
         Self {
-            child: Some(WidgetRef::new(child)),
+            child: WidgetRef::new(child),
             weight,
         }
     }
 
     /// Returns a reference to the child widget.
     #[must_use]
-    pub fn child(&self) -> Option<&WidgetRef> {
-        self.child.as_ref()
+    pub const fn child(&self) -> &WidgetRef {
+        &self.child
     }
 }
 
-impl Widget for Expand {
-    fn redraw(&mut self, context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {
-        let Some(child) = &mut self.child else { return };
-        let child = child.mounted(&mut context.as_event_context());
-        context.for_other(&child).redraw();
+impl WrapperWidget for Expand {
+    fn child(&mut self) -> &mut WidgetRef {
+        &mut self.child
     }
 
-    fn layout(
+    fn layout_child(
         &mut self,
         available_space: Size<ConstraintLimit>,
         context: &mut LayoutContext<'_, '_, '_, '_, '_>,
-    ) -> Size<UPx> {
+    ) -> Rect<Px> {
         let available_space = Size::new(
             ConstraintLimit::Known(available_space.width.max()),
             ConstraintLimit::Known(available_space.height.max()),
         );
-        let child = self
-            .child
-            .as_mut()
-            .map(|child| child.mounted(&mut context.as_event_context()));
-        let size = if let Some(child) = &child {
-            context.for_other(child).layout(available_space)
-        } else {
-            Size::default()
-        };
+        let child = self.child.mounted(&mut context.as_event_context());
+        let size = context.for_other(&child).layout(available_space);
 
-        let expanded_size = Size::new(
+        Size::<UPx>::new(
             available_space
                 .width
                 .fit_measured(size.width, context.graphics.scale()),
             available_space
                 .height
                 .fit_measured(size.height, context.graphics.scale()),
-        );
-
-        if let Some(child) = child {
-            context.set_child_layout(&child, Rect::from(expanded_size.into_signed()));
-        }
-
-        expanded_size
+        )
+        .into_signed()
+        .into()
     }
 }

src/widgets/resize.rs

@@ -1,9 +1,8 @@
-use kludgine::figures::units::UPx;
 use kludgine::figures::{Fraction, IntoSigned, IntoUnsigned, Rect, ScreenScale, Size};
 
-use crate::context::{AsEventContext, GraphicsContext, LayoutContext};
+use crate::context::{AsEventContext, LayoutContext};
 use crate::styles::Dimension;
-use crate::widget::{MakeWidget, Widget, WidgetRef};
+use crate::widget::{MakeWidget, WidgetRef, WrapperWidget};
 use crate::ConstraintLimit;
 
 /// A widget that resizes its contained widget to an explicit size.
@@ -57,17 +56,16 @@ impl Resize {
     }
 }
 
-impl Widget for Resize {
-    fn redraw(&mut self, context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {
-        let child = self.child.mounted(&mut context.as_event_context());
-        context.for_other(&child).redraw();
+impl WrapperWidget for Resize {
+    fn child(&mut self) -> &mut WidgetRef {
+        &mut self.child
     }
 
-    fn layout(
+    fn layout_child(
         &mut self,
         available_space: Size<ConstraintLimit>,
         context: &mut LayoutContext<'_, '_, '_, '_, '_>,
-    ) -> Size<UPx> {
+    ) -> Rect<kludgine::figures::units::Px> {
         let child = self.child.mounted(&mut context.as_event_context());
         let size = if let (Some(width), Some(height)) = (self.width, self.height) {
             Size::new(
@@ -85,8 +83,7 @@ impl Widget for Resize {
             );
             context.for_other(&child).layout(available_space)
         };
-        context.set_child_layout(&child, Rect::from(size.into_signed()));
-        size
+        Rect::from(size.into_signed())
     }
 }
 

src/widgets/space.rs

@@ -0,0 +1,22 @@
+use kludgine::figures::units::UPx;
+use kludgine::figures::Size;
+
+use crate::context::{GraphicsContext, LayoutContext};
+use crate::widget::Widget;
+use crate::ConstraintLimit;
+
+/// A widget that does nothing and draws nothing.
+#[derive(Debug, Clone)]
+pub struct Space;
+
+impl Widget for Space {
+    fn redraw(&mut self, _context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {}
+
+    fn layout(
+        &mut self,
+        _available_space: Size<ConstraintLimit>,
+        _context: &mut LayoutContext<'_, '_, '_, '_, '_>,
+    ) -> Size<UPx> {
+        Size::default()
+    }
+}

src/widgets/stack.rs

@@ -1,5 +1,5 @@
-//! A widget that combines an array of [`Widgets`] into one.
-// TODO on scale change, all Lp children need to resize
+//! A widget that combines a collection of [`Children`] widgets into one.
+// TODO on scale change, all `Lp` children need to resize
 
 use std::ops::Deref;
 
@@ -11,10 +11,10 @@ use crate::context::{AsEventContext, EventContext, GraphicsContext, LayoutContex
 use crate::styles::Dimension;
 use crate::value::{Generation, IntoValue, Value};
 use crate::widget::{Children, ManagedWidget, Widget, WidgetRef};
-use crate::widgets::{Expand, Label, Resize};
+use crate::widgets::{Expand, Resize};
 use crate::ConstraintLimit;
 
-/// A widget that displays a collection of [`Widgets`] in a
+/// A widget that displays a collection of [`Children`] widgets in a
 /// [direction](StackDirection).
 #[derive(Debug)]
 pub struct Stack {
@@ -87,21 +87,12 @@ impl Stack {
                             let guard = widget.lock();
                             let (mut widget, dimension) =
                                 if let Some(expand) = guard.downcast_ref::<Expand>() {
-                                    if let Some(child) = expand.child() {
-                                        (
-                                            child.clone(),
-                                            StackDimension::Fractional {
-                                                weight: expand.weight,
-                                            },
-                                        )
-                                    } else {
-                                        (
-                                            WidgetRef::new(Label::new("")), // TODO this should be an empty widget.
-                                            StackDimension::Fractional {
-                                                weight: expand.weight,
-                                            },
-                                        )
-                                    }
+                                    (
+                                        expand.child().clone(),
+                                        StackDimension::Fractional {
+                                            weight: expand.weight,
+                                        },
+                                    )
                                 } else if let Some((child, size)) =
                                     guard.downcast_ref::<Resize>().and_then(|r| {
                                         match self.layout.orientation.orientation {

src/widgets/style.rs

@@ -1,10 +1,6 @@
-use kludgine::figures::units::UPx;
-use kludgine::figures::Size;
-
-use crate::context::{AsEventContext, EventContext, GraphicsContext, LayoutContext};
+use crate::context::EventContext;
 use crate::styles::Styles;
-use crate::widget::{MakeWidget, Widget, WidgetRef};
-use crate::ConstraintLimit;
+use crate::widget::{MakeWidget, WidgetRef, WrapperWidget};
 
 /// A widget that applies a set of [`Styles`] to all contained widgets.
 #[derive(Debug)]
@@ -24,22 +20,12 @@ impl Style {
     }
 }
 
-impl Widget for Style {
+impl WrapperWidget for Style {
+    fn child(&mut self) -> &mut WidgetRef {
+        &mut self.child
+    }
+
     fn mounted(&mut self, context: &mut EventContext<'_, '_>) {
         context.attach_styles(self.styles.clone());
     }
-
-    fn redraw(&mut self, context: &mut GraphicsContext<'_, '_, '_, '_, '_>) {
-        let child = self.child.mounted(&mut context.as_event_context());
-        context.for_other(&child).redraw();
-    }
-
-    fn layout(
-        &mut self,
-        available_space: Size<ConstraintLimit>,
-        context: &mut LayoutContext<'_, '_, '_, '_, '_>,
-    ) -> Size<UPx> {
-        let child = self.child.mounted(&mut context.as_event_context());
-        context.for_other(&child).layout(available_space)
-    }
 }