Track retained layout validity explicitly

src/widget/text/mod.rs

@@ -47,12 +47,16 @@ impl TextView {
     /// answers under the attrs too, so changing those asks a new question
     /// rather than invalidating anything.
     fn render(&mut self, painter: &mut Painter) -> &RenderedText {
-        let width = if self.attrs.wrap {
-            Some(painter.px_len(Axis::X))
-        } else {
-            None
-        };
-        painter.render_text(&mut self.buf, &self.attrs, width)
+        let width = self.attrs.wrap.then(|| painter.px_len(Axis::X));
+        let text = painter.render_text(&mut self.buf, &self.attrs, width);
+        // A greedy break is the same break at every width from its longest
+        // line up to the one it was made at: each line still fits, and none
+        // could take a word that did not fit in the wider box. A line too
+        // long to fit at all says nothing about narrower boxes.
+        if let Some(width) = width {
+            painter.holds(Axis::X, text.size.x.min(width)..=width);
+        }
+        text
     }
 
     pub fn tex(&self) -> Option<&RenderedText> {
@@ -78,22 +82,6 @@ impl TextView {
         (region, size)
     }
 
-    /// Wrapping reads the width it is offered, so a wider box reshapes it and
-    /// a taller one does not. Alignment matters too, and separately: glyphs
-    /// anchored to the start of an axis stay put when that extent changes,
-    /// but centred or end-aligned ones move even though the shaping stands.
-    pub fn on_resize(&self, axis: Axis) -> OnResize {
-        let reshapes = axis == Axis::X && self.attrs.wrap;
-        let anchored = match axis {
-            Axis::X => self.align.x,
-            Axis::Y => self.align.y,
-        } == AxisAlign::Neg;
-        match reshapes || !anchored {
-            true => OnResize::Redraw,
-            false => OnResize::Translate,
-        }
-    }
-
     pub fn content(&self) -> String {
         self.buf.text().to_string()
     }
@@ -120,10 +108,6 @@ impl Widget for Text {
         self.update_buf();
         self.view.draw(painter).1
     }
-
-    fn on_resize(&self, axis: Axis) -> OnResize {
-        self.view.on_resize(axis)
-    }
 }
 
 impl Deref for Text {