fix: Collapsed panel no longer grows when not pushed by a sibling panel

src/components/SplitPane/hooks/callbacks/useGetMovedSizes.ts

@@ -8,28 +8,52 @@ export function useGetMovedSizes({
   isLtr,
   minSizes,
   collapsedIndices,
+  isReversed,
   collapsedSize,
 }: {
   sizes: number[];
   isLtr: boolean;
   minSizes: number[];
   collapsedIndices: number[];
+  isReversed: boolean;
   collapsedSize: number;
 }) {
   return useCallback(
     (dragState: DragState<ResizeState> | null): number[] => {
       if (!dragState) return originalSizes;
       const sizes = [...originalSizes];
+      const index = dragState.extraState.index;
+      const offset = isLtr ? dragState.offset : -dragState.offset;
       moveSizes({
         sizes: sizes,
-        index: dragState.extraState.index,
-        offset: isLtr ? dragState.offset : -dragState.offset,
+        index,
+        offset,
         minSizes,
         collapsedIndices,
         collapsedSize,
       });
+      // must move all previously collapsed panes as well, slightly different to what happens when collapsing, though mostly identical
+      if (isReversed ? offset > 0 : offset < 0) {
+        for (
+          let i = isReversed ? index : index + 1;
+          isReversed ? i > 0 : i < sizes.length - 1;
+          isReversed ? i-- : i++
+        ) {
+          if (collapsedIndices.includes(i)) {
+            moveSizes({
+              sizes,
+              index: isReversed ? i - 1 : i,
+              offset,
+              minSizes,
+              collapsedIndices,
+              collapsedSize,
+            });
+          }
+        }
+      }
+
       return sizes;
     },
-    [collapsedIndices, collapsedSize, isLtr, minSizes, originalSizes]
+    [collapsedIndices, collapsedSize, isLtr, isReversed, minSizes, originalSizes]
   );
 }

src/components/SplitPane/hooks/useSplitPaneResize.ts

@@ -94,6 +94,7 @@ export function useSplitPaneResize(options: SplitPaneResizeOptions): SplitPaneRe
     isLtr,
     collapsedSize,
     collapsedIndices,
+    isReversed,
   });
   const getCurrentPaneSizes = useGetCurrentPaneSizes({ childPanes, split });
   const handleDragFinished = useHandleDragFinished({ getMovedSizes, children, hooks, setSizes });