Say window where these comments still say frame

Lengths became lengths of the window when the frame did, and `Part::From`'s
own documentation still described its spans as frame lengths -- which is
what the scroll above read them as.

core/src/ui/painter.rs

@@ -541,7 +541,7 @@ impl PrimitiveLike for &TextureHandle {
 /// method's `impl` block is where a `Painter`'s own boxes are, so it takes
 /// only what the child was asked with.
 impl Painter<'_> {
-    /// Frame ranges are already ranges on the window and combine directly.
+    /// Window ranges are already about the one unit and combine directly.
     /// A frame pin becomes this widget's own frame wherever a length of it
     /// is what reached the child; where only pixels did, no length of this
     /// frame can change the child's and the pin stops here.
@@ -563,8 +563,8 @@ impl Painter<'_> {
         let mut result = LayoutHolds::ANY;
         for axis in AXES {
             let n = axis as usize;
-            // Every frame range is already a range on the window: the
+            // Every read became pixels against the window, so a range on
-            // widget's own read converted through its frame exactly once.
+            // it is already in this widget's terms.
             result.window[n] = holds.window[n];
             let reaches = narrow[n].is_none()
                 && !matches!(place[n].part(), Part::Sized(_))
@@ -596,10 +596,10 @@ impl Painter<'_> {
                         _ => self.extent.axis(axis).len(),
                     });
                 }
-                // Its box is a part of this widget's frame, or a length of
+                // Its box is a length this widget decided, from its own
-                // it decided here: a length of the frame is all that reaches
+                // frame or from a sibling's answer: no length of this
-                // it, so what it holds for is a range on the frame and none
+                // widget's box reaches it, so what it holds for is a range
-                // of it on this widget's own box.
+                // on the window and none of it on that box.
                 _ => {
                     result.window[n] =
                         result.window[n].and(holds.extent[n].through(extent.axis(axis).len()));

core/src/ui/place.rs

@@ -5,14 +5,16 @@ use crate::{AxisAlign, Len, PrimitiveHandle, UiRegion, UiSpan};
 pub enum Part {
     /// The whole of it.
     All,
-    /// Frame lengths from where the box starts, which is what a container
+    /// Window lengths from where the box starts, which is what a container
-    /// dividing room among its children speaks: a child's report is a length
+    /// dividing room among its children speaks: a child's report is a window
-    /// of the frame, so the cursor that sums those reports is one too. A
+    /// length, so the cursor that sums those reports is one too. A moved box
-    /// moved box re-places every child by re-adding its start, exactly.
+    /// re-places every child by re-adding its start, exactly. A fraction
+    /// here is a fraction of the window and not of the box -- the whole of a
+    /// box is [`Self::All`], not a `rel(1.0)` span.
     From(UiSpan),
     /// A part of the box in its own coordinates, which is what a container
     /// that insets one speaks: taking eleven pixels off the end needs no
-    /// length, where saying the same thing in frame lengths would make the
+    /// length, where saying the same thing in window lengths would make the
     /// container read its own box -- and a box chosen from its own answer
     /// then feeds back into the answer.
     Of(UiSpan),