Add min_size method to PaneGrid

widget/src/pane_grid/axis.rs

@@ -17,12 +17,19 @@ impl Axis {
         rectangle: &Rectangle,
         ratio: f32,
         spacing: f32,
-    ) -> (Rectangle, Rectangle) {
+        min_size: f32,
+    ) -> (Rectangle, Rectangle, f32) {
         match self {
             Axis::Horizontal => {
-                let height_top =
-                    (rectangle.height * ratio - spacing / 2.0).round();
-                let height_bottom = rectangle.height - height_top - spacing;
+                let height_top = (rectangle.height * ratio - spacing / 2.0)
+                    .round()
+                    .max(min_size)
+                    .min(rectangle.height - min_size);
+
+                let height_bottom =
+                    (rectangle.height - height_top - spacing).max(min_size);
+
+                let ratio = (height_top + spacing / 2.0) / rectangle.height;
 
                 (
                     Rectangle {
@@ -34,12 +41,19 @@ impl Axis {
                         height: height_bottom,
                         ..*rectangle
                     },
+                    ratio,
                 )
             }
             Axis::Vertical => {
-                let width_left =
-                    (rectangle.width * ratio - spacing / 2.0).round();
-                let width_right = rectangle.width - width_left - spacing;
+                let width_left = (rectangle.width * ratio - spacing / 2.0)
+                    .round()
+                    .max(min_size)
+                    .min(rectangle.width - min_size);
+
+                let width_right =
+                    (rectangle.width - width_left - spacing).max(min_size);
+
+                let ratio = (width_left + spacing / 2.0) / rectangle.width;
 
                 (
                     Rectangle {
@@ -51,6 +65,7 @@ impl Axis {
                         width: width_right,
                         ..*rectangle
                     },
+                    ratio,
                 )
             }
         }
@@ -187,7 +202,7 @@ mod tests {
                         width: 10.0,
                         height: overall_height,
                     };
-                    let (top, bottom) = a.split(&r, 0.5, spacing);
+                    let (top, bottom, _ratio) = a.split(&r, 0.5, spacing, 0.0);
                     assert_eq!(
                         top,
                         Rectangle {
@@ -218,7 +233,7 @@ mod tests {
                         width: overall_width,
                         height: 10.0,
                     };
-                    let (left, right) = a.split(&r, 0.5, spacing);
+                    let (left, right, _ratio) = a.split(&r, 0.5, spacing, 0.0);
                     assert_eq!(
                         left,
                         Rectangle {

widget/src/pane_grid/node.rs

@@ -53,17 +53,19 @@ impl Node {
     pub fn pane_regions(
         &self,
         spacing: f32,
-        size: Size,
+        min_size: f32,
+        bounds: Size,
     ) -> BTreeMap<Pane, Rectangle> {
         let mut regions = BTreeMap::new();
 
         self.compute_regions(
             spacing,
+            min_size,
             &Rectangle {
                 x: 0.0,
                 y: 0.0,
-                width: size.width,
-                height: size.height,
+                width: bounds.width,
+                height: bounds.height,
             },
             &mut regions,
         );
@@ -77,17 +79,19 @@ impl Node {
     pub fn split_regions(
         &self,
         spacing: f32,
-        size: Size,
+        min_size: f32,
+        bounds: Size,
     ) -> BTreeMap<Split, (Axis, Rectangle, f32)> {
         let mut splits = BTreeMap::new();
 
         self.compute_splits(
             spacing,
+            min_size,
             &Rectangle {
                 x: 0.0,
                 y: 0.0,
-                width: size.width,
-                height: size.height,
+                width: bounds.width,
+                height: bounds.height,
             },
             &mut splits,
         );
@@ -192,6 +196,7 @@ impl Node {
     fn compute_regions(
         &self,
         spacing: f32,
+        min_size: f32,
         current: &Rectangle,
         regions: &mut BTreeMap<Pane, Rectangle>,
     ) {
@@ -199,10 +204,11 @@ impl Node {
             Node::Split {
                 axis, ratio, a, b, ..
             } => {
-                let (region_a, region_b) = axis.split(current, *ratio, spacing);
+                let (region_a, region_b, _ratio) =
+                    axis.split(current, *ratio, spacing, min_size);
 
-                a.compute_regions(spacing, &region_a, regions);
-                b.compute_regions(spacing, &region_b, regions);
+                a.compute_regions(spacing, min_size, &region_a, regions);
+                b.compute_regions(spacing, min_size, &region_b, regions);
             }
             Node::Pane(pane) => {
                 let _ = regions.insert(*pane, *current);
@@ -213,6 +219,7 @@ impl Node {
     fn compute_splits(
         &self,
         spacing: f32,
+        min_size: f32,
         current: &Rectangle,
         splits: &mut BTreeMap<Split, (Axis, Rectangle, f32)>,
     ) {
@@ -224,12 +231,13 @@ impl Node {
                 b,
                 id,
             } => {
-                let (region_a, region_b) = axis.split(current, *ratio, spacing);
+                let (region_a, region_b, ratio) =
+                    axis.split(current, *ratio, spacing, min_size);
 
-                let _ = splits.insert(*id, (*axis, *current, *ratio));
+                let _ = splits.insert(*id, (*axis, *current, ratio));
 
-                a.compute_splits(spacing, &region_a, splits);
-                b.compute_splits(spacing, &region_b, splits);
+                a.compute_splits(spacing, min_size, &region_a, splits);
+                b.compute_splits(spacing, min_size, &region_b, splits);
             }
             Node::Pane(_) => {}
         }

widget/src/pane_grid/state.rs

@@ -97,10 +97,11 @@ impl<T> State<T> {
     /// Returns the adjacent [`Pane`] of another [`Pane`] in the given
     /// direction, if there is one.
     pub fn adjacent(&self, pane: Pane, direction: Direction) -> Option<Pane> {
-        let regions = self
-            .internal
-            .layout
-            .pane_regions(0.0, Size::new(4096.0, 4096.0));
+        let regions = self.internal.layout.pane_regions(
+            0.0,
+            0.0,
+            Size::new(4096.0, 4096.0),
+        );
 
         let current_region = regions.get(&pane)?;