Replace placement calls with region nodes

core/src/ui/painter.rs

@@ -10,8 +10,6 @@ use crate::{
     ui::render_state::DrawInfo,
     util::Vec2,
 };
-use std::ops::RangeInclusive;
-
 const AXES: [Axis; 2] = [Axis::X, Axis::Y];
 
 /// makes your surfaces look pretty
@@ -40,8 +38,8 @@ pub struct Painter<'a> {
     pub(super) own: [Holds; 2],
     /// What the children it asked about and drew keep it to.
     pub(super) under: [Holds; 2],
-    /// The slot this widget's primitives are positioned through: its own if
-    /// its parent placed it, otherwise the nearest ancestor that has one.
+    /// The movable region this widget's primitives are positioned through:
+    /// its own when opted in, otherwise the nearest ancestor's.
     pub(super) move_idx: MoveIdx,
     pub layer: usize,
     pub(super) depth: usize,
@@ -101,7 +99,7 @@ impl<'a> Painter<'a> {
 
     /// Draws a widget within this widget's region.
     pub fn widget<'s, W: ?Sized>(&'s mut self, id: &'s StrongWidget<W>) -> DrawResult<'s, 'a, W> {
-        self.widget_at(id, UiRegion::FULL, false)
+        self.widget_at(id, UiRegion::FULL)
     }
 
     /// Draws a widget somewhere within this one.
@@ -110,7 +108,7 @@ impl<'a> Painter<'a> {
         id: &'s StrongWidget<W>,
         region: UiRegion,
     ) -> DrawResult<'s, 'a, W> {
-        self.widget_at(id, region, false)
+        self.widget_at(id, region)
     }
 
     /// What a widget declares its lengths to be, which whoever draws it
@@ -125,22 +123,6 @@ impl<'a> Painter<'a> {
         AXES.map(|axis| declared_len(widget, axis))
     }
 
-    /// Draws a child this widget decides the box of, and may decide again
-    /// once it knows what the child came to. The child gets a slot of its
-    /// own, so placing it a second time writes one entry however much it
-    /// drew -- moved or resized alike, since everything under the slot is
-    /// held as a fraction of its box. A child drawn any other way has no slot
-    /// and can only be given a different box by drawing again.
-    pub fn place<'s, W: ?Sized>(
-        &'s mut self,
-        id: &'s StrongWidget<W>,
-        region: UiRegion,
-    ) -> DrawResult<'s, 'a, W> {
-        #[cfg(feature = "layout-diagnostics")]
-        diag::bump(Counter::PlaceCalls);
-        self.widget_at(id, region, true)
-    }
-
     /// Takes back a child that was drawn only to find out how long it is.
     /// Its drawing is dropped and it is not one of this widget's children
     /// this frame; what it answered is still something this widget asked.
@@ -155,8 +137,8 @@ impl<'a> Painter<'a> {
         &'s mut self,
         id: &'s StrongWidget<W>,
         region: UiRegion,
-        slotted: bool,
     ) -> DrawResult<'s, 'a, W> {
+        let region_node = self.rsc.widgets().is_region_node(id.id());
         let declared = self.declared_lens(id);
         // Composing `FULL` through a box is not quite the identity in f32,
         // so a child with nothing declared keeps the box it would have had.
@@ -169,8 +151,9 @@ impl<'a> Painter<'a> {
             false => local.within(&self.region),
         };
         #[cfg(feature = "layout-diagnostics")]
-        if slotted {
-            diag::placed(id.id(), self.id, within);
+        if region_node {
+            diag::bump(Counter::RegionNodeDraws);
+            diag::region_node(id.id(), self.id, within);
         }
         // A child listed twice would be moved twice.
         if !self.children.contains(&id.id()) {
@@ -190,7 +173,7 @@ impl<'a> Painter<'a> {
                 parent: Some(self.id),
                 depth: self.depth + 1,
                 parent_move: self.move_idx,
-                slotted,
+                region_node,
                 mask: self.mask,
                 offer,
                 offered_px: self.px_within_offer(offer),
@@ -371,8 +354,8 @@ impl<'a> Painter<'a> {
     /// holds for -- the same primitives, in the same fractions and offsets
     /// of the box, and the same reported size. A widget that read its
     /// length in pixels holds for that one alone until it says otherwise.
-    pub fn holds(&mut self, axis: Axis, range: RangeInclusive<f32>) {
-        let holds = Holds::from(range);
+    pub fn holds(&mut self, axis: Axis, holds: impl Into<Holds>) {
+        let holds = holds.into();
         debug_assert!(
             holds.contains(self.state.px_of(self.move_idx, self.region).axis(axis)),
             "'{}' ({:?}) says its drawing holds for lengths that leave out its own box",