diff --git a/src/App/App.tsx b/src/App/App.tsx
index b940e9c..520eb62 100644
--- a/src/App/App.tsx
+++ b/src/App/App.tsx
@@ -1,4 +1,4 @@
-import { ReactElement, useEffect, useMemo, useRef, useState } from "react";
+import { ReactElement, useCallback, useEffect, useMemo, useRef, useState } from "react";
 
 import { emptyStatechart, Statechart, Transition } from "../statecharts/abstract_syntax";
 import { handleInputEvent, initialize, RuntimeError } from "../statecharts/interpreter";
@@ -85,9 +85,9 @@ export function App() {
   const plant = plants.find(([pn, p]) => pn === plantName)![1];
 
   const editorState = historyState.current;
-  const setEditorState = (cb: (value: VisualEditorState) => VisualEditorState) => {
+  const setEditorState = useCallback((cb: (value: VisualEditorState) => VisualEditorState) => {
     setHistoryState(historyState => ({...historyState, current: cb(historyState.current)}));
-  }
+  }, [setHistoryState]);
 
   const refRightSideBar = useRef<HTMLDivElement>(null);
 
diff --git a/src/App/KeyInfo.tsx b/src/App/KeyInfo.tsx
index 40e8617..6609d51 100644
--- a/src/App/KeyInfo.tsx
+++ b/src/App/KeyInfo.tsx
@@ -1,6 +1,6 @@
-import { Box, Stack } from "@mui/material";
+import { memo, PropsWithChildren, ReactElement } from "react";
 
-export function KeyInfoVisible(props: {keyInfo, children, horizontal?: boolean}) {
+export const KeyInfoVisible = memo(function KeyInfoVisible(props: PropsWithChildren<{keyInfo: ReactElement, horizontal?: boolean}>) {
   return <div style={{display: 'inline-block'}}>
     {/* <Stack direction={props.horizontal ? "row" : "column"}> */}
       <div style={{display: props.horizontal ? 'inline-block' : '', fontSize:11, height: 18, textAlign:"center", paddingLeft: 3, paddingRight: 3}}>
@@ -11,8 +11,8 @@ export function KeyInfoVisible(props: {keyInfo, children, horizontal?: boolean})
       </div>
     {/* </Stack> */}
   </div>
-}
+});
 
-export function KeyInfoHidden(props: {children}) {
+export const KeyInfoHidden = memo(function KeyInfoHidden(props: PropsWithChildren<{}>) {
   return <>{props.children}</>;
-}
+});
diff --git a/src/App/ShowAST.tsx b/src/App/ShowAST.tsx
index 059d63f..b0e6139 100644
--- a/src/App/ShowAST.tsx
+++ b/src/App/ShowAST.tsx
@@ -32,7 +32,7 @@ export function ShowAction(props: {action: Action}) {
   }
 }
 
-export function ShowAST(props: {root: ConcreteState | PseudoState, transitions: Map<string, Transition[]>, trace: TraceState | null, highlightActive: Set<string>}) {
+export const ShowAST = memo(function ShowAST(props: {root: ConcreteState | PseudoState, transitions: Map<string, Transition[]>, trace: TraceState | null, highlightActive: Set<string>}) {
   const description = stateDescription(props.root);
   // const outgoing = props.transitions.get(props.root.uid) || [];
 
@@ -69,11 +69,11 @@ export function ShowAST(props: {root: ConcreteState | PseudoState, transitions:
   //       outgoing.map(transition => <>&emsp;<ShowTransition transition={transition}/><br/></>)
   //   } */}
   // </details>;
-}
+});
 
 import BoltIcon from '@mui/icons-material/Bolt';
 import { KeyInfoHidden, KeyInfoVisible } from "./KeyInfo";
-import { useEffect } from "react";
+import { memo, useEffect } from "react";
 import { TraceState } from "./App";
 
 export function ShowInputEvents({inputEvents, onRaise, disabled, showKeys}: {inputEvents: EventTrigger[], onRaise: (e: string, p: any) => void, disabled: boolean, showKeys: boolean}) {
diff --git a/src/App/TopPanel.tsx b/src/App/TopPanel.tsx
index 0c63674..3d0f076 100644
--- a/src/App/TopPanel.tsx
+++ b/src/App/TopPanel.tsx
@@ -1,4 +1,4 @@
-import { Dispatch, ReactElement, SetStateAction, useEffect, useState } from "react";
+import { Dispatch, memo, ReactElement, SetStateAction, useEffect, useState } from "react";
 import { BigStep, TimerElapseEvent, Timers } from "../statecharts/runtime_types";
 import { getSimTime, setPaused, setRealtime, TimeMode } from "../statecharts/time";
 import { Statechart } from "../statecharts/abstract_syntax";
@@ -11,12 +11,8 @@ import SkipNextIcon from '@mui/icons-material/SkipNext';
 import SkipPreviousIcon from '@mui/icons-material/SkipPrevious';import TrendingFlatIcon from '@mui/icons-material/TrendingFlat';
 import AccessAlarmIcon from '@mui/icons-material/AccessAlarm';
 import StopIcon from '@mui/icons-material/Stop';
-import UndoIcon from '@mui/icons-material/Undo';
-import RedoIcon from '@mui/icons-material/Redo';
 import InfoOutlineIcon from '@mui/icons-material/InfoOutline';
 import KeyboardIcon from '@mui/icons-material/Keyboard';
-import ZoomInIcon from '@mui/icons-material/ZoomIn';
-import ZoomOutIcon from '@mui/icons-material/ZoomOut';
 
 import { formatTime } from "./util";
 import { InsertMode } from "../VisualEditor/VisualEditor";
@@ -26,20 +22,20 @@ 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";
 
 export type TopPanelProps = {
   trace: TraceState | null,
-  // rt?: BigStep,
-  // rtIdx?: number,
   time: TimeMode,
   setTime: Dispatch<SetStateAction<TimeMode>>,
   onUndo: () => void,
   onRedo: () => void,
   onInit: () => void,
   onClear: () => void,
-  onRaise: (e: string, p: any) => void,
+  // onRaise: (e: string, p: any) => void,
   onBack: () => void,
-  ast: Statechart,
+  // ast: Statechart,
   mode: InsertMode,
   setMode: Dispatch<SetStateAction<InsertMode>>,
   setModal: Dispatch<SetStateAction<ReactElement|null>>,
@@ -50,7 +46,7 @@ export type TopPanelProps = {
   history: EditHistory,
 }
 
-export function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear, onRaise, onBack, ast, mode, setMode, setModal, zoom, setZoom, showKeys, setShowKeys, history}: TopPanelProps) {
+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);
 
@@ -111,14 +107,6 @@ export function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear,
           e.preventDefault();
           onRedo();
         }
-        if (e.key === "+") {
-          e.preventDefault();
-          onZoomIn();
-        }
-        if (e.key === "-") {
-          e.preventDefault();
-          onZoomOut();
-        }
       }
     };
     window.addEventListener("keydown", onKeyDown);
@@ -143,12 +131,6 @@ export function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear,
     }
   }, [time]);
 
-  function onZoomIn() {
-    setZoom(zoom => Math.min(zoom * ZOOM_STEP, ZOOM_MAX));
-  }
-  function onZoomOut() {
-    setZoom(zoom => Math.max(zoom / ZOOM_STEP, ZOOM_MIN));
-  }
 
   function onChangePaused(paused: boolean, wallclktime: number) {
     setTime(time => {
@@ -218,24 +200,13 @@ export function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear,
 
     {/* zoom */}
     <div className="toolbarGroup">
-      <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>-</kbd></>}>
-        <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></>}>
-        <button title="zoom in" onClick={onZoomIn} disabled={zoom >= ZOOM_MAX}><ZoomInIcon fontSize="small"/></button>
-      </KeyInfo>
+      <ZoomButtons showKeys={showKeys} zoom={zoom} setZoom={setZoom}/>
       &emsp;
     </div>
 
     {/* undo / redo */}
     <div className="toolbarGroup">
-      <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Z</kbd></>}>
-        <button title="undo" onClick={onUndo} disabled={history.history.length === 0}><UndoIcon fontSize="small"/>&nbsp;({history.history.length})</button>
-      </KeyInfo>
-      <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>Z</kbd></>}>
-        <button title="redo" onClick={onRedo} disabled={history.future.length === 0}><RedoIcon fontSize="small"/>&nbsp;({history.future.length})</button>
-      </KeyInfo>
+      <UndoRedoButtons showKeys={showKeys} onUndo={onUndo} onRedo={onRedo} historyLength={history.history.length} futureLength={history.future.length}/>
       &emsp;
     </div>
 
@@ -349,4 +320,4 @@ export function TopPanel({trace, time, setTime, onUndo, onRedo, onInit, onClear,
     </div> */}
 
   </div>;
-}
+});
diff --git a/src/App/TopPanel/UndoRedoButtons.tsx b/src/App/TopPanel/UndoRedoButtons.tsx
new file mode 100644
index 0000000..de8d3be
--- /dev/null
+++ b/src/App/TopPanel/UndoRedoButtons.tsx
@@ -0,0 +1,17 @@
+import { memo } from "react";
+import { KeyInfoHidden, KeyInfoVisible } from "../KeyInfo";
+
+import UndoIcon from '@mui/icons-material/Undo';
+import RedoIcon from '@mui/icons-material/Redo';
+
+export const UndoRedoButtons = memo(function UndoRedoButtons({showKeys, onUndo, onRedo, historyLength, futureLength}: {showKeys: boolean, onUndo: () => void, onRedo: () => void, historyLength: number, futureLength: number}) {
+  const KeyInfo = showKeys ? KeyInfoVisible : KeyInfoHidden;
+  return <>
+    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Z</kbd></>}>
+      <button title="undo" onClick={onUndo} disabled={historyLength === 0}><UndoIcon fontSize="small"/>&nbsp;({historyLength})</button>
+    </KeyInfo>
+    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>Z</kbd></>}>
+      <button title="redo" onClick={onRedo} disabled={futureLength === 0}><RedoIcon fontSize="small"/>&nbsp;({futureLength})</button>
+    </KeyInfo>
+  </>;
+});
diff --git a/src/App/TopPanel/ZoomButtons.tsx b/src/App/TopPanel/ZoomButtons.tsx
new file mode 100644
index 0000000..0930b18
--- /dev/null
+++ b/src/App/TopPanel/ZoomButtons.tsx
@@ -0,0 +1,47 @@
+import { ZOOM_MAX, ZOOM_MIN, ZOOM_STEP } from "@/VisualEditor/parameters";
+import { Dispatch, memo, SetStateAction, useEffect } from "react";
+import { KeyInfoHidden, KeyInfoVisible } from "../KeyInfo";
+
+import ZoomInIcon from '@mui/icons-material/ZoomIn';
+import ZoomOutIcon from '@mui/icons-material/ZoomOut';
+
+export const ZoomButtons = memo(function ZoomButtons({showKeys, zoom, setZoom}: {showKeys: boolean, zoom: number, setZoom: Dispatch<SetStateAction<number>>}) {
+
+  const KeyInfo = showKeys ? KeyInfoVisible : KeyInfoHidden;
+
+  function onZoomIn() {
+    setZoom(zoom => Math.min(zoom * ZOOM_STEP, ZOOM_MAX));
+  }
+  function onZoomOut() {
+    setZoom(zoom => Math.max(zoom / ZOOM_STEP, ZOOM_MIN));
+  }
+  
+  useEffect(() => {
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.ctrlKey) {
+          if (e.key === "+") {
+          e.preventDefault();
+          onZoomIn();
+        }
+        if (e.key === "-") {
+          e.preventDefault();
+          onZoomOut();
+        }
+      }
+    };
+    window.addEventListener("keydown", onKeyDown);
+    return () => {
+      window.removeEventListener("keydown", onKeyDown);
+    };
+  }, []);
+
+  return <>
+    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>-</kbd></>}>
+      <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></>}>
+      <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 b77882c..a998a99 100644
--- a/src/VisualEditor/ArrowSVG.tsx
+++ b/src/VisualEditor/ArrowSVG.tsx
@@ -1,9 +1,10 @@
+import { memo } from "react";
 import { Arrow } from "../statecharts/concrete_syntax";
 import { ArcDirection, euclideanDistance } from "./geometry";
 import { CORNER_HELPER_RADIUS } from "./parameters";
 
 
-export function ArrowSVG(props: { arrow: Arrow; selected: string[]; errors: string[]; highlight: boolean; fired: boolean; arc: ArcDirection; initialMarker: boolean }) {
+export const ArrowSVG = memo(function(props: { arrow: Arrow; selected: string[]; errors: 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";
@@ -78,4 +79,4 @@ export function ArrowSVG(props: { arrow: Arrow; selected: string[]; errors: stri
       data-parts="end" />}
 
   </g>;
-}
+});
diff --git a/src/VisualEditor/DiamondSVG.tsx b/src/VisualEditor/DiamondSVG.tsx
index 608c1f8..5052ba8 100644
--- a/src/VisualEditor/DiamondSVG.tsx
+++ b/src/VisualEditor/DiamondSVG.tsx
@@ -1,9 +1,10 @@
 import { Diamond, RountanglePart } from "@/statecharts/concrete_syntax";
 import { rountangleMinSize } from "./VisualEditor";
-import { Rect2D, Vec2D } from "./geometry";
+import { Vec2D } from "./geometry";
 import { RectHelper } from "./RectHelpers";
+import { memo } from "react";
 
-export function DiamondShape(props: {size: Vec2D, extraAttrs: object}) {
+export const DiamondShape = memo(function DiamondShape(props: {size: Vec2D, extraAttrs: object}) {
   const minSize = rountangleMinSize(props.size);
   return <polygon
     points={`
@@ -17,9 +18,9 @@ export function DiamondShape(props: {size: Vec2D, extraAttrs: object}) {
     strokeWidth={2}
     {...props.extraAttrs}
   />;
-}
+});
 
-export function DiamondSVG(props: { diamond: Diamond; selected: string[]; highlight: RountanglePart[]; errors: string[]; active: boolean; }) {
+export const DiamondSVG = memo(function DiamondSVG(props: { diamond: Diamond; selected: string[]; highlight: RountanglePart[]; errors: string[]; active: boolean; }) {
   const minSize = rountangleMinSize(props.diamond.size);
   const extraAttrs = {
     className: ''
@@ -38,4 +39,4 @@ export function DiamondSVG(props: { diamond: Diamond; selected: string[]; highli
 
     <RectHelper uid={props.diamond.uid} size={minSize} highlight={props.highlight} selected={props.selected} />
   </g>;
-}
+});
diff --git a/src/VisualEditor/HistorySVG.tsx b/src/VisualEditor/HistorySVG.tsx
index 6ca1be1..b6b3d7b 100644
--- a/src/VisualEditor/HistorySVG.tsx
+++ b/src/VisualEditor/HistorySVG.tsx
@@ -1,7 +1,8 @@
+import { memo } from "react";
 import { Vec2D } from "./geometry";
 import { HISTORY_RADIUS } from "./parameters";
 
-export function HistorySVG(props: {uid: string, topLeft: Vec2D, kind: "shallow"|"deep", selected: boolean, highlight: boolean}) {
+export const HistorySVG = memo(function HistorySVG(props: {uid: string, topLeft: Vec2D, kind: "shallow"|"deep", selected: boolean, highlight: boolean}) {
   const text = props.kind === "shallow" ? "H" : "H*";
   return <>
     <circle
@@ -38,4 +39,4 @@ export function HistorySVG(props: {uid: string, topLeft: Vec2D, kind: "shallow"|
         data-parts="history"
       />}
   </>;
-}
+});
diff --git a/src/VisualEditor/RectHelpers.tsx b/src/VisualEditor/RectHelpers.tsx
index 06b25c3..6272c5c 100644
--- a/src/VisualEditor/RectHelpers.tsx
+++ b/src/VisualEditor/RectHelpers.tsx
@@ -1,3 +1,4 @@
+import { memo } from "react";
 import { RountanglePart } from "../statecharts/concrete_syntax";
 import { Vec2D } from "./geometry";
 import { CORNER_HELPER_OFFSET, CORNER_HELPER_RADIUS } from "./parameters";
@@ -11,7 +12,7 @@ function lineGeometryProps(size: Vec2D): [RountanglePart, object][] {
   ];
 }
 
-export function RectHelper(props: { uid: string, size: Vec2D, selected: string[], highlight: RountanglePart[] }) {
+export const RectHelper = memo(function RectHelper(props: { uid: string, size: Vec2D, selected: string[], highlight: RountanglePart[] }) {
   const geomProps = lineGeometryProps(props.size);
   return <>
     {geomProps.map(([side, ps]) => <g key={side}>
@@ -53,4 +54,4 @@ export function RectHelper(props: { uid: string, size: Vec2D, selected: string[]
       data-uid={props.uid}
       data-parts="bottom left" />
   </>;
-}
\ No newline at end of file
+});
\ No newline at end of file
diff --git a/src/VisualEditor/RountangleSVG.tsx b/src/VisualEditor/RountangleSVG.tsx
index 51ca578..278ee14 100644
--- a/src/VisualEditor/RountangleSVG.tsx
+++ b/src/VisualEditor/RountangleSVG.tsx
@@ -1,10 +1,11 @@
+import { memo } from "react";
 import { Rountangle, RountanglePart } from "../statecharts/concrete_syntax";
 import { ROUNTANGLE_RADIUS } from "./parameters";
 import { RectHelper } from "./RectHelpers";
 import { rountangleMinSize } from "./VisualEditor";
 
 
-export function RountangleSVG(props: { rountangle: Rountangle; selected: string[]; highlight: RountanglePart[]; errors: string[]; active: boolean; }) {
+export const RountangleSVG = memo(function RountangleSVG(props: {rountangle: Rountangle; selected: string[]; highlight: RountanglePart[]; errors: string[]; active: boolean; }) {
   const { topLeft, size, uid } = props.rountangle;
   // always draw a rountangle with a minimum size
   // during resizing, rountangle can be smaller than this size and even have a negative size, but we don't show it
@@ -37,4 +38,4 @@ export function RountangleSVG(props: { rountangle: Rountangle; selected: string[
       selected={props.selected}
       highlight={props.highlight} />
   </g>;
-}
+})
diff --git a/src/VisualEditor/TextSVG.tsx b/src/VisualEditor/TextSVG.tsx
index 87b68cd..b2287a7 100644
--- a/src/VisualEditor/TextSVG.tsx
+++ b/src/VisualEditor/TextSVG.tsx
@@ -1,9 +1,9 @@
 import { TextDialog } from "@/App/TextDialog";
 import { TraceableError } from "..//statecharts/parser";
 import {Text} from "../statecharts/concrete_syntax";
-import { Dispatch, ReactElement, SetStateAction } from "react";
+import { Dispatch, memo, ReactElement, SetStateAction } from "react";
 
-export function TextSVG(props: {text: Text, error: TraceableError|undefined, selected: boolean, highlight: boolean, onEdit: (newText: string) => void, setModal: Dispatch<SetStateAction<ReactElement|null>>}) {
+export const TextSVG = memo(function TextSVG(props: {text: Text, error: TraceableError|undefined, selected: boolean, highlight: boolean, onEdit: (text: Text, newText: string) => void, setModal: Dispatch<SetStateAction<ReactElement|null>>}) {
   const commonProps = {
     "data-uid": props.text.uid,
     "data-parts": "text",
@@ -37,11 +37,11 @@ export function TextSVG(props: {text: Text, error: TraceableError|undefined, sel
     onDoubleClick={() => {
       props.setModal(<TextDialog setModal={props.setModal} text={props.text.text} done={newText => {
           if (newText) {
-            props.onEdit(newText);
+            props.onEdit(props.text, newText);
           }
       }} />)
     }}>
       {textNode}
       <text className="draggableText helper" textAnchor="middle" data-uid={props.text.uid} data-parts="text" style={{whiteSpace: "preserve"}}>{props.text.text}</text>
     </g>;
-}
\ No newline at end of file
+});
diff --git a/src/VisualEditor/VisualEditor.tsx b/src/VisualEditor/VisualEditor.tsx
index 1a9d1a3..fe367ef 100644
--- a/src/VisualEditor/VisualEditor.tsx
+++ b/src/VisualEditor/VisualEditor.tsx
@@ -1,9 +1,8 @@
-import { ClipboardEvent, Dispatch, ReactElement, SetStateAction, useEffect, useMemo, useRef, useState } from "react";
+import { ClipboardEvent, Dispatch, memo, ReactElement, SetStateAction, useCallback, useEffect, useMemo, useRef, useState } from "react";
 
 import { Statechart } from "../statecharts/abstract_syntax";
 import { Arrow, ArrowPart, Diamond, History, Rountangle, RountanglePart, Text } from "../statecharts/concrete_syntax";
 import { parseStatechart, TraceableError } from "../statecharts/parser";
-import { BigStep } from "../statecharts/runtime_types";
 import { ArcDirection, Line2D, Rect2D, Vec2D, addV2D, arcDirection, area, getBottomSide, getLeftSide, getRightSide, getTopSide, isEntirelyWithin, normalizeRect, scaleV2D, subtractV2D, transformLine, transformRect } from "./geometry";
 import { MIN_ROUNTANGLE_SIZE } from "./parameters";
 import { getBBoxInSvgCoords } from "./svg_helper";
@@ -64,7 +63,7 @@ export type InsertMode = "and"|"or"|"pseudo"|"shallow"|"deep"|"transition"|"text
 type VisualEditorProps = {
   state: VisualEditorState,
   setState: Dispatch<(v:VisualEditorState) => VisualEditorState>,
-  ast: Statechart,
+  // ast: Statechart,
   setAST: Dispatch<SetStateAction<Statechart>>,
   trace: TraceState | null,
   errors: TraceableError[],
@@ -77,7 +76,7 @@ type VisualEditorProps = {
   zoom: number;
 };
 
-export function VisualEditor({state, setState, ast, setAST, trace, errors, setErrors, mode, highlightActive, highlightTransitions, setModal, makeCheckPoint, zoom}: VisualEditorProps) {
+export const VisualEditor = memo(function VisualEditor({state, setState, setAST, trace, errors, setErrors, mode, highlightActive, highlightTransitions, setModal, makeCheckPoint, zoom}: VisualEditorProps) {
 
   const [dragging, setDragging] = useState(false);
 
@@ -642,7 +641,7 @@ export function VisualEditor({state, setState, ast, setAST, trace, errors, setEr
     }
   }
 
-  function onEditText(text: Text, newText: string) {
+  const onEditText = useCallback((text: Text, newText: string) => {
     if (newText === "") {
       // delete text node
       setState(state => ({
@@ -666,8 +665,9 @@ export function VisualEditor({state, setState, ast, setAST, trace, errors, setEr
         }),
       }));
     }
-  }
+  }, [setState]);
 
+  // @ts-ignore
   const active = trace && trace.trace[trace.idx].mode || new Set();
 
   const rootErrors = errors.filter(({shapeUid}) => shapeUid === "root").map(({message}) => message);
@@ -774,14 +774,14 @@ export function VisualEditor({state, setState, ast, setAST, trace, errors, setEr
         text={txt}
         selected={Boolean(selection.find(s => s.uid === txt.uid)?.parts?.length)}
         highlight={textsToHighlight.hasOwnProperty(txt.uid)}
-        onEdit={newText => onEditText(txt, newText)}
+        onEdit={onEditText}
         setModal={setModal}
       />
     })}
 
     {selectingState && <Selecting {...selectingState} />}
   </svg>;
-}
+});
 
 export function rountangleMinSize(size: Vec2D): Vec2D {
   if (size.x >= 40 && size.y >= 40) {
diff --git a/todo.txt b/todo.txt
index d506807..b18377b 100644
--- a/todo.txt
+++ b/todo.txt
@@ -53,6 +53,8 @@ TODO
 
 - experimental features:
     - multiverse execution history
+        stable tree layout?
+            https://pub.dev/packages/ploeg_tree_layout
     - local scopes