diff --git a/src/App/TopPanel.tsx b/src/App/TopPanel.tsx
index 3d0f076..cf4223d 100644
--- a/src/App/TopPanel.tsx
+++ b/src/App/TopPanel.tsx
@@ -18,9 +18,7 @@ import { formatTime } from "./util";
 import { InsertMode } from "../VisualEditor/VisualEditor";
 import { KeyInfoHidden, KeyInfoVisible } from "./KeyInfo";
 import { About } from "./About";
-import { usePersistentState } from "@/util/persistent_state";
 import { RountangleIcon, PseudoStateIcon, HistoryIcon } from "./Icons";
-import { ZOOM_MAX, ZOOM_MIN, ZOOM_STEP } from "@/VisualEditor/parameters";
 import { EditHistory, TraceState } from "./App";
 import { ZoomButtons } from "./TopPanel/ZoomButtons";
 import { UndoRedoButtons } from "./TopPanel/UndoRedoButtons";
@@ -46,6 +44,18 @@ export type TopPanelProps = {
   history: EditHistory,
 }
 
+const ShortCutShowKeys = <kbd>~</kbd>;
+
+const insertModes: [InsertMode, string, ReactElement, ReactElement][] = [
+  ["and", "AND-states", <RountangleIcon kind="and"/>, <kbd>A</kbd>],
+  ["or", "OR-states", <RountangleIcon kind="or"/>, <kbd>O</kbd>],
+  ["pseudo", "pseudo-states", <PseudoStateIcon/>, <kbd>P</kbd>],
+  ["shallow", "shallow history", <HistoryIcon kind="shallow"/>, <kbd>H</kbd>],
+  ["deep", "deep history", <HistoryIcon kind="deep"/>, <></>],
+  ["transition", "transitions", <TrendingFlatIcon fontSize="small"/>, <kbd>T</kbd>],
+  ["text", "text", <>&nbsp;T&nbsp;</>, <kbd>X</kbd>],
+];
+
 export const TopPanel = memo(function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear, onBack, mode, setMode, setModal, zoom, setZoom, showKeys, setShowKeys, history}: TopPanelProps) {
   const [displayTime, setDisplayTime] = useState("0.000");
   const [timescale, setTimescale] = useState(1);
@@ -191,7 +201,7 @@ export const TopPanel = memo(function TopPanel({trace, time, setTime, onUndo, on
 
     {/* shortcuts / about */}
     <div className="toolbarGroup">
-      <KeyInfo keyInfo={<kbd>~</kbd>}>
+      <KeyInfo keyInfo={ShortCutShowKeys}>
         <button title="show/hide keyboard shortcuts" className={showKeys?"active":""} onClick={() => setShowKeys(s => !s)}><KeyboardIcon fontSize="small"/></button>
       </KeyInfo>
       <button title="about StateBuddy" onClick={() => setModal(<About setModal={setModal}/>)}><InfoOutlineIcon fontSize="small"/></button>
@@ -212,15 +222,7 @@ export const TopPanel = memo(function TopPanel({trace, time, setTime, onUndo, on
 
     {/* insert rountangle / arrow / ... */}
     <div className="toolbarGroup">
-      {([
-        ["and", "AND-states", <RountangleIcon kind="and"/>, <kbd>A</kbd>],
-        ["or", "OR-states", <RountangleIcon kind="or"/>, <kbd>O</kbd>],
-        ["pseudo", "pseudo-states", <PseudoStateIcon/>, <kbd>P</kbd>],
-        ["shallow", "shallow history", <HistoryIcon kind="shallow"/>, <kbd>H</kbd>],
-        ["deep", "deep history", <HistoryIcon kind="deep"/>, <></>],
-        ["transition", "transitions", <TrendingFlatIcon fontSize="small"/>, <kbd>T</kbd>],
-        ["text", "text", <>&nbsp;T&nbsp;</>, <kbd>X</kbd>],
-      ] as [InsertMode, string, ReactElement, ReactElement][]).map(([m, hint, buttonTxt, keyInfo]) =>
+      {insertModes.map(([m, hint, buttonTxt, keyInfo]) =>
         <KeyInfo key={m} keyInfo={keyInfo}>
         <button
           title={"insert "+hint}
diff --git a/src/App/TopPanel/ZoomButtons.tsx b/src/App/TopPanel/ZoomButtons.tsx
index 0930b18..503e3ba 100644
--- a/src/App/TopPanel/ZoomButtons.tsx
+++ b/src/App/TopPanel/ZoomButtons.tsx
@@ -5,6 +5,9 @@ import { KeyInfoHidden, KeyInfoVisible } from "../KeyInfo";
 import ZoomInIcon from '@mui/icons-material/ZoomIn';
 import ZoomOutIcon from '@mui/icons-material/ZoomOut';
 
+const shortcutZoomIn = <><kbd>Ctrl</kbd>+<kbd>-</kbd></>;
+const shortcutZoomOut = <><kbd>Ctrl</kbd>+<kbd>+</kbd></>;
+
 export const ZoomButtons = memo(function ZoomButtons({showKeys, zoom, setZoom}: {showKeys: boolean, zoom: number, setZoom: Dispatch<SetStateAction<number>>}) {
 
   const KeyInfo = showKeys ? KeyInfoVisible : KeyInfoHidden;
@@ -36,11 +39,11 @@ export const ZoomButtons = memo(function ZoomButtons({showKeys, zoom, setZoom}:
   }, []);
 
   return <>
-    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>-</kbd></>}>
+    <KeyInfo keyInfo={shortcutZoomOut}>
       <button title="zoom out" onClick={onZoomOut} disabled={zoom <= ZOOM_MIN}><ZoomOutIcon fontSize="small"/></button>
     </KeyInfo>
     <input title="current zoom level" value={zoom.toFixed(3)} style={{width:40}} readOnly/>
-    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>+</kbd></>}>
+    <KeyInfo keyInfo={shortcutZoomIn}>
       <button title="zoom in" onClick={onZoomIn} disabled={zoom >= ZOOM_MAX}><ZoomInIcon fontSize="small"/></button>
     </KeyInfo>
   </>;
diff --git a/src/VisualEditor/ArrowSVG.tsx b/src/VisualEditor/ArrowSVG.tsx
index a998a99..709ca76 100644
--- a/src/VisualEditor/ArrowSVG.tsx
+++ b/src/VisualEditor/ArrowSVG.tsx
@@ -1,10 +1,11 @@
 import { memo } from "react";
-import { Arrow } from "../statecharts/concrete_syntax";
+import { Arrow, ArrowPart } from "../statecharts/concrete_syntax";
 import { ArcDirection, euclideanDistance } from "./geometry";
 import { CORNER_HELPER_RADIUS } from "./parameters";
+import { arraysEqual } from "@/App/util";
 
 
-export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: string[]; errors: string[]; highlight: boolean; fired: boolean; arc: ArcDirection; initialMarker: boolean }) {
+export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: ArrowPart[]; error: string; highlight: boolean; fired: boolean; arc: ArcDirection; initialMarker: boolean }) {
   const { start, end, uid } = props.arrow;
   const radius = euclideanDistance(start, end) / 1.6;
   let largeArc = "1";
@@ -18,7 +19,7 @@ export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: string[];
     <path
       className={"arrow"
         + (props.selected.length === 2 ? " selected" : "")
-        + (props.errors.length > 0 ? " error" : "")
+        + (props.error ? " error" : "")
         + (props.highlight ? " highlight" : "")
         + (props.fired ? " fired" : "")
       }
@@ -30,13 +31,13 @@ export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: string[];
       data-uid={uid}
       data-parts="start end" />
 
-    {props.errors.length > 0 && <text
+    {props.error && <text
       className="error"
       x={(start.x + end.x) / 2 + 5}
       y={(start.y + end.y) / 2}
       textAnchor="middle"
       data-uid={uid}
-      data-parts="start end">{props.errors.join(', ')}</text>}
+      data-parts="start end">{props.error}</text>}
 
     <path
       className="helper"
@@ -79,4 +80,12 @@ export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: string[];
       data-parts="end" />}
 
   </g>;
-});
+}, (prevProps, nextProps) => {
+  return prevProps.arrow === nextProps.arrow
+    && arraysEqual(prevProps.selected, nextProps.selected)
+    && prevProps.highlight === nextProps.highlight
+    && prevProps.error === nextProps.error
+    && prevProps.fired === nextProps.fired
+    && prevProps.arc === nextProps.arc
+    && prevProps.initialMarker === nextProps.initialMarker
+})
diff --git a/src/VisualEditor/VisualEditor.tsx b/src/VisualEditor/VisualEditor.tsx
index f41abf2..56c8cd6 100644
--- a/src/VisualEditor/VisualEditor.tsx
+++ b/src/VisualEditor/VisualEditor.tsx
@@ -755,10 +755,10 @@ export const VisualEditor = memo(function VisualEditor({state, setState, setAST,
       return <ArrowSVG
         key={arrow.uid}
         arrow={arrow}
-        selected={selection.find(a => a.uid === arrow.uid)?.parts || []}
-        errors={errors
+        selected={selection.find(a => a.uid === arrow.uid)?.parts as ArrowPart[] || []}
+        error={errors
           .filter(({shapeUid}) => shapeUid === arrow.uid)
-          .map(({message}) => message)}
+          .map(({message}) => message).join(', ')}
         highlight={arrowsToHighlight.hasOwnProperty(arrow.uid)}
         fired={highlightTransitions.includes(arrow.uid)}
         arc={arc}
diff --git a/src/util/persistent_state.ts b/src/util/persistent_state.ts
index 8046c56..d59681e 100644
--- a/src/util/persistent_state.ts
+++ b/src/util/persistent_state.ts
@@ -1,4 +1,4 @@
-import { Dispatch, SetStateAction, useState } from "react";
+import { Dispatch, SetStateAction, useCallback, useState } from "react";
 
 // like useState, but it is persisted in localStorage
 // important: values must be JSON-(de-)serializable
@@ -18,7 +18,7 @@ export function usePersistentState<T>(key: string, initial: T): [T, Dispatch<Set
     return initial;
   });
 
-  function setStateWrapped(val: SetStateAction<T>) {
+  const setStateWrapped = useCallback((val: SetStateAction<T>) => {
     setState((oldState: T) => {
       let newVal;
       if (typeof val === 'function') {
@@ -32,7 +32,7 @@ export function usePersistentState<T>(key: string, initial: T): [T, Dispatch<Set
       localStorage.setItem(key, serialized);
       return newVal;
     });
-  }
+  }, [setState]);
 
   return [state, setStateWrapped];
 }