feat: do not break polygon on point delete inside line editor (#9580)

* feat: do not break polygon on point delete inside line editor

* fix: polygon point highlighting when selected point == 0

packages/element/src/linearElementEditor.ts

@@ -1290,24 +1290,19 @@ export class LinearElementEditor {
       app.state.editingLinearElement?.lastUncommittedPoint ===
       element.points[element.points.length - 1];
 
-    const isPolygon = isLineElement(element) && element.polygon;
-
-    // break polygon if deleting start/end point
-    if (
-      isPolygon &&
-      // don't disable polygon if cleaning up uncommitted point
-      !isUncommittedPoint &&
-      (pointIndices.includes(0) ||
-        pointIndices.includes(element.points.length - 1))
-    ) {
-      app.scene.mutateElement(element, { polygon: false });
-    }
-
     const nextPoints = element.points.filter((_, idx) => {
       return !pointIndices.includes(idx);
     });
 
-    if (isUncommittedPoint && isLineElement(element) && element.polygon) {
+    const isPolygon = isLineElement(element) && element.polygon;
+
+    // keep polygon intact if deleting start/end point or uncommitted point
+    if (
+      isPolygon &&
+      (isUncommittedPoint ||
+        pointIndices.includes(0) ||
+        pointIndices.includes(element.points.length - 1))
+    ) {
       nextPoints[0] = pointFrom(
         nextPoints[nextPoints.length - 1][0],
         nextPoints[nextPoints.length - 1][1],

packages/excalidraw/renderer/interactiveScene.ts

@@ -459,18 +459,27 @@ const renderLinearPointHandles = (
 
     const isOverlappingPoint =
       idx > 0 &&
-      (idx !== points.length - 1 ||
+      (idx !== points.length - 1 || !_isLineElement || !element.polygon) &&
-        appState.editingLinearElement ||
-        !_isLineElement ||
-        !element.polygon) &&
       pointsEqual(
         point,
         idx === points.length - 1 ? points[0] : points[idx - 1],
         2 / appState.zoom.value,
       );
 
-    const isSelected =
+    let isSelected =
       !!appState.editingLinearElement?.selectedPointsIndices?.includes(idx);
+    // when element is a polygon, highlight the last point as well if first
+    // point is selected since they overlap and the last point tends to be
+    // rendered on top
+    if (
+      _isLineElement &&
+      element.polygon &&
+      !isSelected &&
+      idx === element.points.length - 1 &&
+      !!appState.editingLinearElement?.selectedPointsIndices?.includes(0)
+    ) {
+      isSelected = true;
+    }
 
     renderSingleLinearPoint(
       context,