Call the record's boxes what they are

The offer names are from the protocol before this one, where a widget was
drawn twice and the record had to say which drawing was the question. It
is asked once now, so offer_part is the part it was asked in, offer_place
the place it was asked at, and place where its drawing was put: part,
asked and placed. LayoutHolds::frame is a range on the window since the
frame became a length of one, and the frame's own entry is the frame_len
pin beside it, so it is window; Painter::frame_own goes with it.
answers_at had one caller and said less than the line that replaces it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/src/ui/active.rs

@@ -19,17 +19,17 @@ pub struct ActiveData {
     /// forwards the parent's frame. What it declared is kept separately in
     /// `declared` and is a fraction of whichever of the two reached it.
     pub narrow: [Option<Len>; 2],
-    /// Where its drawing was put, as a part of its parent's box, and where
-    /// it was asked. The two differ where a container asks in one place and
-    /// places the answer in another -- a row measures from its cursor and
+    /// Where its drawing was put, and where it was asked, each as a part of
+    /// its parent's box. The two differ where a container asks in one place
+    /// and puts the answer in another -- a row measures from its cursor and
     /// puts the child in its slot. A part is a length from the box's start,
     /// so a box that moved re-places every child by re-adding that start.
-    pub place: [Place; 2],
-    pub offer_place: [Place; 2],
+    pub placed: [Place; 2],
+    pub asked: [Place; 2],
     /// The box it was asked in, in the parent's region-node coordinates: the
     /// box its drawing was made in and the one its contract is about. Its
     /// drawing is placed elsewhere by re-expression, never by asking again.
-    pub offer_part: UiRegion,
+    pub part: UiRegion,
     /// The measured answer and its dependencies. A hint-only dependency or
     /// a widget first encountered during placement has no measurement yet.
     pub answer: Option<(Size, LayoutHolds)>,
@@ -82,20 +82,10 @@ pub struct ActiveData {
 }
 
 impl ActiveData {
-    /// What it answered when its parent measured it, where it has been
-    /// measured at all. Not `size`, which is what its last drawing reported:
-    /// a drawing made in the box that answer chose is answering a different
-    /// question.
+    /// What it answered when its parent asked, where it has been asked at
+    /// all. Not `size`, which is what its last drawing reported: a drawing
+    /// re-expressed in the box that answer chose is not a second answer.
     pub fn measured(&self) -> Option<Size> {
         self.answer.map(|(size, _)| size)
     }
-
-    /// Whether what it answered still stands in this window, for the frame
-    /// and the box it was asked in. The answer was given in the box its
-    /// parent first asked about, which is what it is checked against --
-    /// `holds` on the record is about the box the answer then chose.
-    pub fn answers_at(&self, window: crate::PxVec2, part: UiRegion) -> bool {
-        self.answer
-            .is_some_and(|(_, holds)| holds.contains(window, self.frame, part))
-    }
 }

core/src/ui/layout_holds.rs

@@ -20,7 +20,7 @@ const AXES: [Axis; 2] = [Axis::X, Axis::Y];
 /// whatever the frame turns out to be.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct LayoutHolds {
-    pub frame: [Holds; 2],
+    pub window: [Holds; 2],
     pub frame_len: [Option<Len>; 2],
     pub extent: [Holds; 2],
     pub extent_len: [Option<Len>; 2],
@@ -28,7 +28,7 @@ pub struct LayoutHolds {
 
 impl LayoutHolds {
     pub const ANY: Self = Self {
-        frame: [Holds::ANY; 2],
+        window: [Holds::ANY; 2],
         frame_len: [None; 2],
         extent: [Holds::ANY; 2],
         extent_len: [None; 2],
@@ -37,7 +37,7 @@ impl LayoutHolds {
     pub fn and(self, other: Self) -> Self {
         let mut result = Self::ANY;
         for n in 0..2 {
-            result.frame[n] = self.frame[n].and(other.frame[n]);
+            result.window[n] = self.window[n].and(other.window[n]);
             result.extent[n] = self.extent[n].and(other.extent[n]);
             debug_assert!(
                 self.extent_len[n].is_none()
@@ -57,8 +57,8 @@ impl LayoutHolds {
 
     pub fn covers(self, other: Self) -> bool {
         (0..2).all(|n| {
-            self.frame[n].lo <= other.frame[n].lo
-                && self.frame[n].hi >= other.frame[n].hi
+            self.window[n].lo <= other.window[n].lo
+                && self.window[n].hi >= other.window[n].hi
                 && self.extent[n].lo <= other.extent[n].lo
                 && self.extent[n].hi >= other.extent[n].hi
                 && self.extent_len[n].is_none_or(|len| other.extent_len[n] == Some(len))
@@ -70,7 +70,7 @@ impl LayoutHolds {
         AXES.into_iter().all(|axis| {
             let n = axis as usize;
             let len = extent.axis(axis).len();
-            self.frame[n].contains(window.axis(axis))
+            self.window[n].contains(window.axis(axis))
                 && self.frame_len[n].is_none_or(|pinned| pinned == frame.axis(axis))
                 && self.extent[n].contains(len.to_px(window.axis(axis)))
                 && self.extent_len[n].is_none_or(|pinned| pinned == len)

core/src/ui/painter.rs

@@ -42,7 +42,7 @@ pub struct Painter<'a> {
     pub(super) size_deps: Vec<WidgetId>,
     /// What this draw itself read of the window in pixels, per axis: every
     /// window until it reads one, then that one, unless it says otherwise.
-    pub(super) frame_own: [Holds; 2],
+    pub(super) window_own: [Holds; 2],
     /// Its frame's symbolic length where this draw read it, which makes the
     /// drawing one that holds for that frame alone.
     pub(super) frame_own_len: [Option<Len>; 2],
@@ -192,8 +192,8 @@ impl<'a> Painter<'a> {
                 mask: self.mask,
                 frame,
                 part: extent,
-                place,
-                offer_place: place,
+                placed: place,
+                asked: place,
                 narrow,
                 re_asked,
                 px,
@@ -429,7 +429,7 @@ impl<'a> Painter<'a> {
     pub fn to_px(&mut self, len: Len, axis: Axis) -> Px {
         let window = self.window.axis(axis);
         if len.rel != Rel::ZERO {
-            let own = &mut self.frame_own[axis as usize];
+            let own = &mut self.window_own[axis as usize];
             if *own == Holds::ANY {
                 *own = Holds::at(window);
             }
@@ -437,8 +437,10 @@ impl<'a> Painter<'a> {
         len.to_px(window)
     }
 
-    /// A validity range already stated about the window. Containers use
-    /// this after branching on a window-unit length.
+    /// The windows this drawing holds for, stated rather than taken: a
+    /// container that branched on a length in pixels says which side of the
+    /// boundary it was on, which is wider than the one window reading that
+    /// length pins, and replaces it.
     pub fn window_holds(&mut self, axis: Axis, holds: impl Into<Holds>) {
         let holds = holds.into();
         debug_assert!(
@@ -447,7 +449,7 @@ impl<'a> Painter<'a> {
             self.label(),
             self.id
         );
-        self.frame_own[axis as usize] = holds;
+        self.window_own[axis as usize] = holds;
     }
 
     pub fn text_data(&mut self) -> &mut TextData {
@@ -563,7 +565,7 @@ impl Painter<'_> {
             let n = axis as usize;
             // Every frame range is already a range on the window: the
             // widget's own read converted through its frame exactly once.
-            result.frame[n] = holds.frame[n];
+            result.window[n] = holds.window[n];
             let reaches = narrow[n].is_none()
                 && !matches!(place[n].part(), Part::Sized(_))
                 && declared[n].is_none_or(|len| len.rel != Rel::ZERO);
@@ -599,8 +601,8 @@ impl Painter<'_> {
                 // it, so what it holds for is a range on the frame and none
                 // of it on this widget's own box.
                 _ => {
-                    result.frame[n] =
-                        result.frame[n].and(holds.extent[n].through(extent.axis(axis).len()));
+                    result.window[n] =
+                        result.window[n].and(holds.extent[n].through(extent.axis(axis).len()));
                 }
             }
         }

core/src/ui/render_state.rs

@@ -28,9 +28,9 @@ pub(super) struct DrawInfo {
     pub part: UiRegion,
     /// Where the widget is put, and where it was asked, as parts of the
     /// parent's box. See [`Place`]. The two are one ask's place until the
-    /// parent places the answer somewhere else.
-    pub place: [Place; 2],
-    pub offer_place: [Place; 2],
+    /// parent puts the answer somewhere else.
+    pub placed: [Place; 2],
+    pub asked: [Place; 2],
     /// A frame the parent decided for it on each axis, as a length of the
     /// window, which the widget's own declaration is a fraction of.
     pub narrow: [Option<Len>; 2],
@@ -44,7 +44,7 @@ impl DrawInfo {
     /// The axes where the part is the drawing's box outright, which are the
     /// axes the answer is not placed inside it again.
     fn fill(&self) -> [bool; 2] {
-        self.place.map(Place::fills)
+        self.placed.map(Place::fills)
     }
 }
 
@@ -120,9 +120,13 @@ impl UiRenderState {
         let Some(root) = self.old_root else { return };
         let stands = self.active.get(&root).is_some_and(|active| {
             // Nothing above the root chose anything, so the box it was first
-            // asked about is the whole of its frame.
-            active.answers_at(size, active.offer_part)
-                && active.holds.contains(size, active.frame, active.offer_part)
+            // asked about is the whole of its frame. Both its answer and its
+            // drawing have to stand in the new window, since nothing above
+            // it will ask either again.
+            let answer = active
+                .answer
+                .is_some_and(|(_, holds)| holds.contains(size, active.frame, active.part));
+            answer && active.holds.contains(size, active.frame, active.part)
         });
         if !stands {
             widgets.needs_redraw.insert(root);
@@ -142,8 +146,8 @@ impl UiRenderState {
             mask: MaskIdx::NONE,
             frame,
             part: extent,
-            place: [Place::Within(Part::All); 2],
-            offer_place: [Place::Within(Part::All); 2],
+            placed: [Place::Within(Part::All); 2],
+            asked: [Place::Within(Part::All); 2],
             narrow: [None; 2],
             re_asked: false,
             px,
@@ -267,9 +271,9 @@ impl UiRenderState {
         active.narrow = info.narrow;
         active.re_asked = info.re_asked;
         active.answer = Some(answer);
-        active.offer_place = info.offer_place;
-        active.offer_part = part;
-        active.place = info.place;
+        active.asked = info.asked;
+        active.part = part;
+        active.placed = info.placed;
         active.own_align = align;
         // A subtree can be reused whole under a different parent -- same box,
         // same layer, same region node -- and nothing in the drawing says it
@@ -328,7 +332,7 @@ impl UiRenderState {
             mask_region: None,
             children: Vec::new(),
             size_deps: Vec::new(),
-            frame_own: [Holds::ANY; 2],
+            window_own: [Holds::ANY; 2],
             frame_own_len: [None; 2],
             under: Vec::new(),
             extent_own: [Holds::ANY; 2],
@@ -364,7 +368,7 @@ impl UiRenderState {
             answer_under,
             children,
             size_deps,
-            frame_own,
+            window_own,
             frame_own_len,
             under,
             move_idx,
@@ -435,7 +439,7 @@ impl UiRenderState {
             }
         });
         let own_holds = LayoutHolds {
-            frame: frame_own,
+            window: window_own,
             frame_len,
             extent: extent_own,
             extent_len,
@@ -465,8 +469,8 @@ impl UiRenderState {
                         mask,
                         frame: UiVec2::FULL_SIZE,
                         part: UiRegion::FULL,
-                        place: [Place::Within(Part::All); 2],
-                        offer_place: [Place::Within(Part::All); 2],
+                        placed: [Place::Within(Part::All); 2],
+                        asked: [Place::Within(Part::All); 2],
                         narrow: [None; 2],
                         re_asked: false,
                         px,
@@ -482,9 +486,9 @@ impl UiRenderState {
             extent,
             frame: info.frame,
             narrow: info.narrow,
-            place: info.place,
-            offer_place: info.offer_place,
-            offer_part: extent,
+            placed: info.placed,
+            asked: info.asked,
+            part: extent,
             // Whoever asked writes the answer.
             answer: None,
             re_asked: info.re_asked,
@@ -626,7 +630,7 @@ impl UiRenderState {
                     if holds.extent_len[n].is_some_and(|pinned| pinned != part.axis(axis).len()) {
                         diag::bump(Counter::OutsidePinnedLen);
                     }
-                    if !holds.frame[n].contains(self.output_size.axis(axis))
+                    if !holds.window[n].contains(self.output_size.axis(axis))
                         || holds.frame_len[n].is_some_and(|pinned| pinned != info.frame.axis(axis))
                     {
                         diag::bump(Counter::OutsideFrame);
@@ -672,7 +676,7 @@ impl UiRenderState {
         self.redepth(id, info.depth);
         let active = self.active.get_mut(&id).unwrap();
         active.frame = info.frame;
-        active.place = info.place;
+        active.placed = info.placed;
         #[cfg(feature = "layout-diagnostics")]
         {
             match (moved, has_region_node) {
@@ -697,7 +701,7 @@ impl UiRenderState {
 
     /// Places one child of `at.id` where that widget's own box now has it.
     fn place_child(&mut self, child: WidgetId, at: &Placing, rsc: &mut dyn UiRsc) {
-        let place = self.active[&child].place;
+        let place = self.active[&child].placed;
         self.place_in(child, at, place, rsc);
     }
 
@@ -729,8 +733,8 @@ impl UiRenderState {
             mask: at.mask,
             frame,
             part,
-            place,
-            offer_place: active.offer_place,
+            placed: place,
+            asked: active.asked,
             narrow: active.narrow,
             re_asked: active.re_asked,
             px: frame.to_px(at.window),
@@ -874,9 +878,9 @@ impl UiRenderState {
                 extent: UiRegion::FULL,
                 frame: UiVec2::FULL_SIZE,
                 narrow: [None; 2],
-                place: [Place::Within(Part::All); 2],
-                offer_place: [Place::Within(Part::All); 2],
-                offer_part: UiRegion::FULL,
+                placed: [Place::Within(Part::All); 2],
+                asked: [Place::Within(Part::All); 2],
+                part: UiRegion::FULL,
                 answer: None,
                 re_asked: false,
                 size,
@@ -1113,14 +1117,14 @@ impl UiRenderState {
             self.draw_inner(id, info, old, rsc);
             return true;
         };
-        let (was_answer, was_holds, was_place) = (active.answer, active.holds, active.place);
+        let (was_answer, was_holds, was_place) = (active.answer, active.holds, active.placed);
         // The question its parent asked, asked again: the same place of the
         // box the parent was asked in, which is the box the parent's own
         // draw ran in and what its children's parts are of. Where the
         // parent's answer put its own drawing is not a question anybody
         // asked, and nothing is asked in it here either.
-        let asked = self.placing_of(parent, self.active[&parent].offer_part);
-        let (frame, part) = Self::ask_again(active, &asked, active.offer_place);
+        let parent_at = self.placing_of(parent, self.active[&parent].part);
+        let (frame, part) = Self::ask_again(active, &parent_at, active.asked);
         let info = DrawInfo {
             layer: active.layer,
             parent: active.parent,
@@ -1130,8 +1134,8 @@ impl UiRenderState {
             mask: active.parent_mask,
             frame,
             part,
-            place: active.offer_place,
-            offer_place: active.offer_place,
+            placed: active.asked,
+            asked: active.asked,
             narrow: active.narrow,
             re_asked: false,
             px: frame.to_px(self.output_size),