From 689179f428300b4097a0ff110dd57e6692f2c12d Mon Sep 17 00:00:00 2001
From: Mark Tolmacs <mark@lazycat.hu>
Date: Sat, 15 Mar 2025 11:33:45 +0100
Subject: [PATCH] Fix single selected arrow highlight after delete, undo, redo

---
 .../actions/actionDuplicateSelection.tsx      | 22 ++++++++
 .../excalidraw/renderer/interactiveScene.ts   | 52 ++++++++++++-------
 2 files changed, 56 insertions(+), 18 deletions(-)

diff --git a/packages/excalidraw/actions/actionDuplicateSelection.tsx b/packages/excalidraw/actions/actionDuplicateSelection.tsx
index 2d61d1c0b..194980f2c 100644
--- a/packages/excalidraw/actions/actionDuplicateSelection.tsx
+++ b/packages/excalidraw/actions/actionDuplicateSelection.tsx
@@ -96,6 +96,7 @@ export const actionDuplicateSelection = register({
       elements: nextElements,
       appState: {
         ...appState,
+        ...updateLinearElementEditors(nextElements),
         ...selectGroupsForSelectedElements(
           {
             editingGroupId: appState.editingGroupId,
@@ -131,3 +132,24 @@ export const actionDuplicateSelection = register({
     />
   ),
 });
+
+const updateLinearElementEditors = (clonedElements: ExcalidrawElement[]) => {
+  const linears = clonedElements.filter(isLinearElement);
+  if (linears.length === 1) {
+    const linear = linears[0];
+    const boundElements = linear.boundElements?.map((def) => def.id) ?? [];
+    const onlySingleLinearSelected = clonedElements.every(
+      (el) => el.id === linear.id || boundElements.includes(el.id),
+    );
+
+    if (onlySingleLinearSelected) {
+      return {
+        selectedLinearElement: new LinearElementEditor(linear),
+      };
+    }
+  }
+
+  return {
+    selectedLinearElement: null,
+  };
+};
diff --git a/packages/excalidraw/renderer/interactiveScene.ts b/packages/excalidraw/renderer/interactiveScene.ts
index 257decd62..0bbfc92b1 100644
--- a/packages/excalidraw/renderer/interactiveScene.ts
+++ b/packages/excalidraw/renderer/interactiveScene.ts
@@ -51,7 +51,13 @@ import {
 } from "../scene/scrollbars";
 import { getCornerRadius } from "../shapes";
 import { type InteractiveCanvasAppState } from "../types";
-import { arrayToMap, invariant, throttleRAF } from "../utils";
+import {
+  arrayToMap,
+  invariant,
+  isDevEnv,
+  isTestEnv,
+  throttleRAF,
+} from "../utils";
 
 import {
   bootstrapCanvas,
@@ -886,23 +892,33 @@ const _renderInteractiveScene = ({
     );
   }
 
-  if (
-    isElbowArrow(selectedElements[0]) &&
-    appState.selectedLinearElement &&
-    appState.selectedLinearElement.segmentMidPointHoveredCoords
-  ) {
-    renderElbowArrowMidPointHighlight(context, appState);
-  } else if (
-    appState.selectedLinearElement &&
-    appState.selectedLinearElement.hoverPointIndex >= 0 &&
-    !(
-      isElbowArrow(selectedElements[0]) &&
-      appState.selectedLinearElement.hoverPointIndex > 0 &&
-      appState.selectedLinearElement.hoverPointIndex <
-        selectedElements[0].points.length - 1
-    )
-  ) {
-    renderLinearElementPointHighlight(context, appState, elementsMap);
+  // Arrows have a different highlight behavior when
+  // they are the only selected element
+  if (appState.selectedLinearElement) {
+    if (isTestEnv() || isDevEnv()) {
+      invariant(
+        selectedElements.length <= 1,
+        `There is an active selectedLinearElement on app state but the selectedElements length is ${selectedElements?.length} not 1`,
+      );
+    }
+
+    const editor = appState.selectedLinearElement;
+    const firstSelectedLinear = selectedElements.find(
+      (el) => el.id === editor.elementId, // Don't forget bound text elements!
+    );
+
+    if (isElbowArrow(firstSelectedLinear)) {
+      if (editor.segmentMidPointHoveredCoords) {
+        renderElbowArrowMidPointHighlight(context, appState);
+      } else if (
+        editor.hoverPointIndex !== 0 &&
+        editor.hoverPointIndex !== firstSelectedLinear.points.length - 1
+      ) {
+        renderLinearElementPointHighlight(context, appState, elementsMap);
+      }
+    } else if (editor.hoverPointIndex >= 0) {
+      renderLinearElementPointHighlight(context, appState, elementsMap);
+    }
   }
 
   // Paint selected elements