From de6250b0cda67c74ee92543cad227a4aad8f694e Mon Sep 17 00:00:00 2001
From: Steven Hugg <hugg@fasterlight.com>
Date: Fri, 10 Nov 2023 10:38:30 -0600
Subject: [PATCH] show raster x/y crosshair when stopped
 (getRasterCanvasPosition)

---
 javatari.js                |   2 +-
 src/common/baseplatform.ts |  28 +++-
 src/common/devices.ts      | 289 +++++++++++++++++++------------------
 src/common/emu.ts          |  15 ++
 src/machine/astrocade.ts   |   1 +
 src/machine/atari7800.ts   |  12 +-
 src/machine/atari8.ts      |  10 +-
 src/machine/c64.ts         |   9 ++
 src/machine/cpc.ts         |   6 +
 src/machine/vic20.ts       |   6 +
 src/platform/vcs.ts        |  36 ++++-
 11 files changed, 254 insertions(+), 160 deletions(-)

diff --git a/javatari.js b/javatari.js
index 9d124f08..113cd574 160000
--- a/javatari.js
+++ b/javatari.js
@@ -1 +1 @@
-Subproject commit 9d124f087e1f0c7f74f9244b9679cc62e71fa524
+Subproject commit 113cd5741e5c414bbbe47ef8be7a896652d48f64
diff --git a/src/common/baseplatform.ts b/src/common/baseplatform.ts
index 7c5db5e0..af8e232d 100644
--- a/src/common/baseplatform.ts
+++ b/src/common/baseplatform.ts
@@ -1,5 +1,5 @@
 
-import { RasterVideo, dumpRAM, AnimationTimer, ControllerPoller } from "./emu";
+import { RasterVideo, dumpRAM, AnimationTimer, ControllerPoller, drawCrosshair } from "./emu";
 import { hex, printFlags, invertMap, byteToASCII } from "./util";
 import { CodeAnalyzer } from "./analysis";
 import { Segment, FileData } from "./workertypes";
@@ -850,7 +850,7 @@ export abstract class BaseMachinePlatform<T extends Machine> extends BaseDebugPl
       }
     }
   }
-  
+
   loadROM(title, data) {
     this.machine.loadROM(data, title);
     this.reset();
@@ -873,11 +873,26 @@ export abstract class BaseMachinePlatform<T extends Machine> extends BaseDebugPl
   advance(novideo:boolean) {
     let trap = this.getDebugCallback();
     var steps = this.machine.advanceFrame(trap);
-    if (!novideo && this.video) this.video.updateFrame();
-    if (!novideo && this.serialVisualizer) this.serialVisualizer.refresh();
+    if (!novideo && this.video) {
+      this.video.updateFrame();
+      this.updateVideoDebugger();
+    }
+    if (!novideo && this.serialVisualizer) {
+      this.serialVisualizer.refresh();
+    }
     return steps;
   }
 
+  updateVideoDebugger() {
+    if (!this.isRunning() && isRaster(this.machine) && this.machine.getRasterCanvasPosition) {
+      const {x,y} = this.machine.getRasterCanvasPosition();
+      if (x >= 0 || y >= 0) {
+        const ctx = this.video.getContext();
+        drawCrosshair(ctx, x, y, 1);
+      }
+    }
+  }
+
   advanceFrameClock(trap, step) {
     if (!(step > 0)) return;
     if (this.machine instanceof BaseWASMMachine) {
@@ -915,7 +930,10 @@ export abstract class BaseMachinePlatform<T extends Machine> extends BaseDebugPl
 
   // TODO: reset target clock counter
   getRasterScanline() {
-    return isRaster(this.machine) && this.machine.getRasterY();
+    return isRaster(this.machine) && this.machine.getRasterY ? this.machine.getRasterY() : -1;
+  }
+  getRasterLineClock() {
+    return isRaster(this.machine) && this.machine.getRasterX ? this.machine.getRasterX() : -1;
   }
 
   readAddress(addr : number) : number {
diff --git a/src/common/devices.ts b/src/common/devices.ts
index cc62ddf6..f0cac962 100644
--- a/src/common/devices.ts
+++ b/src/common/devices.ts
@@ -1,115 +1,116 @@
 
 export interface SavesState<S> {
-    saveState() : S;
-    loadState(state:S) : void;
+  saveState(): S;
+  loadState(state: S): void;
 }
 
 export interface Bus {
-    read(a:number) : number;
-    write(a:number, v:number) : void;
-    readConst?(a:number) : number;
+  read(a: number): number;
+  write(a: number, v: number): void;
+  readConst?(a: number): number;
 }
 
 export interface ClockBased {
-    advanceClock() : void;
+  advanceClock(): void;
 }
 
 export interface InstructionBased {
-    advanceInsn() : number;
+  advanceInsn(): number;
 }
 
 export type TrapCondition = () => boolean;
 
 export interface FrameBased {
-    advanceFrame(trap:TrapCondition) : number;
+  advanceFrame(trap: TrapCondition): number;
 }
 
 export interface VideoSource {
-  getVideoParams() : VideoParams;
-  connectVideo(pixels:Uint32Array) : void;
+  getVideoParams(): VideoParams;
+  connectVideo(pixels: Uint32Array): void;
 }
 
 export interface RasterFrameBased extends FrameBased, VideoSource {
-  getRasterY() : number;
-  getRasterX() : number;
+  getRasterY(): number;
+  getRasterX(): number;
+  getRasterCanvasPosition?(): { x: number, y: number };
 }
 
 export interface VideoParams {
-    width : number;
-    height : number;
-    overscan? : boolean;
-    rotate? : number;
-    videoFrequency? : number; // default = 60
-    aspect? : number;
+  width: number;
+  height: number;
+  overscan?: boolean;
+  rotate?: number;
+  videoFrequency?: number; // default = 60
+  aspect?: number;
 }
 
 // TODO: frame buffer optimization (apple2, etc)
 
 export interface SampledAudioParams {
-    sampleRate : number;
-    stereo : boolean;
+  sampleRate: number;
+  stereo: boolean;
 }
 
 export interface SampledAudioSink {
-    feedSample(value:number, count:number) : void;
-    //sendAudioFrame(samples:Uint16Array) : void;
+  feedSample(value: number, count: number): void;
+  //sendAudioFrame(samples:Uint16Array) : void;
 }
 
 export interface SampledAudioSource {
-    getAudioParams() : SampledAudioParams;
-    connectAudio(audio : SampledAudioSink) : void;
+  getAudioParams(): SampledAudioParams;
+  connectAudio(audio: SampledAudioSink): void;
 }
 
 export interface AcceptsROM {
-    loadROM(data:Uint8Array, title?:string) : void;
+  loadROM(data: Uint8Array, title?: string): void;
 }
 
 export interface AcceptsBIOS {
-  loadBIOS(data:Uint8Array, title?:string) : void;
+  loadBIOS(data: Uint8Array, title?: string): void;
 }
 
 export interface Resettable {
-    reset() : void;
+  reset(): void;
 }
 
 export interface MemoryBusConnected {
-    connectMemoryBus(bus:Bus) : void;
+  connectMemoryBus(bus: Bus): void;
 }
 
 export interface IOBusConnected {
-    connectIOBus(bus:Bus) : void;
+  connectIOBus(bus: Bus): void;
 }
 
 export interface CPU extends MemoryBusConnected, Resettable, SavesState<any> {
-    getPC() : number;
-    getSP() : number;
-    isStable() : boolean;
+  getPC(): number;
+  getSP(): number;
+  isStable(): boolean;
 }
 
 export interface HasCPU extends Resettable {
-    cpu : CPU;
+  cpu: CPU;
 }
 
 export interface Interruptable<IT> {
-    interrupt(type:IT) : void;
+  interrupt(type: IT): void;
 }
 
 export interface SavesInputState<CS> {
-    loadControlsState(cs:CS) : void;
-    saveControlsState() : CS;
+  loadControlsState(cs: CS): void;
+  saveControlsState(): CS;
 }
 
 export interface AcceptsKeyInput {
-    setKeyInput(key:number, code:number, flags:number) : void;
+  setKeyInput(key: number, code: number, flags: number): void;
 }
 
 export interface AcceptsPaddleInput {
-    setPaddleInput(controller:number, value:number) : void;
+  setPaddleInput(controller: number, value: number): void;
 }
 
 // TODO: interface not yet used (setKeyInput() handles joystick)
 export interface AcceptsJoyInput {
-  setJoyInput(joy:number, bitmask:number) : void;
+  setJoyInput(joy: number, bitmask: number): void;
 }
 
 // SERIAL I/O
@@ -123,15 +124,15 @@ export interface SerialEvent {
 // TODO: all these needed?
 export interface SerialIOInterface {
   // from machine to platform
-  clearToSend() : boolean;
-  sendByte(b : number);
+  clearToSend(): boolean;
+  sendByte(b: number);
   // from platform to machine
-  byteAvailable() : boolean;
-  recvByte() : number;
+  byteAvailable(): boolean;
+  recvByte(): number;
   // implement these too
-  reset() : void;
-  advance(clocks: number) : void;
-//  refresh() : void;
+  reset(): void;
+  advance(clocks: number): void;
+  //  refresh() : void;
 }
 
 export interface HasSerialIO {
@@ -143,62 +144,62 @@ export interface HasSerialIO {
 /// PROFILER
 
 export interface Probeable {
-    connectProbe(probe: ProbeAll) : void;
+  connectProbe(probe: ProbeAll): void;
 }
 
 export interface ProbeTime {
-  logClocks(clocks:number);
+  logClocks(clocks: number);
   logNewScanline();
   logNewFrame();
 }
 
 export interface ProbeCPU {
-  logExecute(address:number, SP:number);
-  logInterrupt(type:number);
-  logIllegal(address:number);
-  logWait(address:number);
+  logExecute(address: number, SP: number);
+  logInterrupt(type: number);
+  logIllegal(address: number);
+  logWait(address: number);
 }
 
 export interface ProbeBus {
-  logRead(address:number, value:number);
-  logWrite(address:number, value:number);
-  logDMARead(address:number, value:number);
-  logDMAWrite(address:number, value:number);
+  logRead(address: number, value: number);
+  logWrite(address: number, value: number);
+  logDMARead(address: number, value: number);
+  logDMAWrite(address: number, value: number);
 }
 
 export interface ProbeIO {
-  logIORead(address:number, value:number);
-  logIOWrite(address:number, value:number);
+  logIORead(address: number, value: number);
+  logIOWrite(address: number, value: number);
 }
 
 export interface ProbeVRAM {
-  logVRAMRead(address:number, value:number);
-  logVRAMWrite(address:number, value:number);
+  logVRAMRead(address: number, value: number);
+  logVRAMWrite(address: number, value: number);
 }
 
 export interface ProbeAll extends ProbeTime, ProbeCPU, ProbeBus, ProbeIO, ProbeVRAM {
-  logData(data:number); // entire 32 bits
+  logData(data: number); // entire 32 bits
   addLogBuffer(src: Uint32Array);
 }
 
 export class NullProbe implements ProbeAll {
-  logClocks()		{}
-  logNewScanline()	{}
-  logNewFrame()		{}
-  logExecute()		{}
-  logInterrupt()	{}
-  logRead()		{}
-  logWrite()		{}
-  logIORead()		{}
-  logIOWrite()		{}
-  logVRAMRead()		{}
-  logVRAMWrite()	{}
-  logIllegal()		{}
-  logWait()		{}
-  logDMARead()		{}
-  logDMAWrite()		{}
-  logData()       {}
-  addLogBuffer(src: Uint32Array) {}
+  logClocks() { }
+  logNewScanline() { }
+  logNewFrame() { }
+  logExecute() { }
+  logInterrupt() { }
+  logRead() { }
+  logWrite() { }
+  logIORead() { }
+  logIOWrite() { }
+  logVRAMRead() { }
+  logVRAMWrite() { }
+  logIllegal() { }
+  logWait() { }
+  logDMARead() { }
+  logDMAWrite() { }
+  logData() { }
+  addLogBuffer(src: Uint32Array) { }
 }
 
 /// CONVENIENCE
@@ -215,32 +216,32 @@ export interface BasicMachineState extends BasicMachineControlsState {
 export abstract class BasicHeadlessMachine implements HasCPU, Bus, AcceptsROM, Probeable,
   SavesState<BasicMachineState>, SavesInputState<BasicMachineControlsState> {
 
-  abstract cpuFrequency : number;
-  abstract defaultROMSize : number;
+  abstract cpuFrequency: number;
+  abstract defaultROMSize: number;
 
-  abstract cpu : CPU;
-  abstract ram : Uint8Array;  
+  abstract cpu: CPU;
+  abstract ram: Uint8Array;
 
-  rom : Uint8Array;
-  inputs : Uint8Array = new Uint8Array(32);
-  handler : (key,code,flags) => void; // keyboard handler
+  rom: Uint8Array;
+  inputs: Uint8Array = new Uint8Array(32);
+  handler: (key, code, flags) => void; // keyboard handler
 
   nullProbe = new NullProbe();
-  probe : ProbeAll = this.nullProbe;
-  
-  abstract read(a:number) : number;
-  abstract write(a:number, v:number) : void;
+  probe: ProbeAll = this.nullProbe;
 
-  setKeyInput(key:number, code:number, flags:number) : void {
-    this.handler && this.handler(key,code,flags);
+  abstract read(a: number): number;
+  abstract write(a: number, v: number): void;
+
+  setKeyInput(key: number, code: number, flags: number): void {
+    this.handler && this.handler(key, code, flags);
   }
-  connectProbe(probe: ProbeAll) : void {
+  connectProbe(probe: ProbeAll): void {
     this.probe = probe || this.nullProbe;
   }
   reset() {
     this.cpu.reset();
   }
-  loadROM(data:Uint8Array, title?:string) : void {
+  loadROM(data: Uint8Array, title?: string): void {
     if (!this.rom) this.rom = new Uint8Array(this.defaultROMSize);
     this.rom.set(data);
   }
@@ -251,9 +252,9 @@ export abstract class BasicHeadlessMachine implements HasCPU, Bus, AcceptsROM, P
   }
   saveState() {
     return {
-      c:this.cpu.saveState(),
-      ram:this.ram.slice(0),
-      inputs:this.inputs.slice(0),
+      c: this.cpu.saveState(),
+      ram: this.ram.slice(0),
+      inputs: this.inputs.slice(0),
     };
   }
   loadControlsState(state) {
@@ -261,7 +262,7 @@ export abstract class BasicHeadlessMachine implements HasCPU, Bus, AcceptsROM, P
   }
   saveControlsState() {
     return {
-      inputs:this.inputs.slice(0)
+      inputs: this.inputs.slice(0)
     };
   }
   advanceCPU() {
@@ -273,102 +274,104 @@ export abstract class BasicHeadlessMachine implements HasCPU, Bus, AcceptsROM, P
     this.probe.logClocks(n);
     return n;
   }
-  probeMemoryBus(membus:Bus) : Bus {
+  probeMemoryBus(membus: Bus): Bus {
     return {
       read: (a) => {
         let val = membus.read(a);
-        this.probe.logRead(a,val);
+        this.probe.logRead(a, val);
         return val;
       },
-      write: (a,v) => {
-        this.probe.logWrite(a,v);
-        membus.write(a,v);
+      write: (a, v) => {
+        this.probe.logWrite(a, v);
+        membus.write(a, v);
       }
     };
   }
-  connectCPUMemoryBus(membus:Bus) : void {
+  connectCPUMemoryBus(membus: Bus): void {
     this.cpu.connectMemoryBus(this.probeMemoryBus(membus));
   }
-  probeIOBus(iobus:Bus) : Bus {
+  probeIOBus(iobus: Bus): Bus {
     return {
       read: (a) => {
         let val = iobus.read(a);
-        this.probe.logIORead(a,val);
+        this.probe.logIORead(a, val);
         return val;
       },
-      write: (a,v) => {
-        this.probe.logIOWrite(a,v);
-        iobus.write(a,v);
+      write: (a, v) => {
+        this.probe.logIOWrite(a, v);
+        iobus.write(a, v);
       }
     };
   }
-  probeDMABus(iobus:Bus) : Bus {
+  probeDMABus(iobus: Bus): Bus {
     return {
       read: (a) => {
         let val = iobus.read(a);
-        this.probe.logDMARead(a,val);
+        this.probe.logDMARead(a, val);
         return val;
       },
-      write: (a,v) => {
-        this.probe.logDMAWrite(a,v);
-        iobus.write(a,v);
+      write: (a, v) => {
+        this.probe.logDMAWrite(a, v);
+        iobus.write(a, v);
       }
     };
   }
-  connectCPUIOBus(iobus:Bus) : void {
+  connectCPUIOBus(iobus: Bus): void {
     this.cpu['connectIOBus'](this.probeIOBus(iobus));
   }
 }
 
 export abstract class BasicMachine extends BasicHeadlessMachine implements SampledAudioSource {
 
-  abstract canvasWidth : number;
-  abstract numVisibleScanlines : number;
-  abstract sampleRate : number;
-  overscan : boolean = false;
-  rotate : number = 0;
-  aspectRatio : number;
-  
-  pixels : Uint32Array;
-  audio : SampledAudioSink;
+  abstract canvasWidth: number;
+  abstract numVisibleScanlines: number;
+  abstract sampleRate: number;
+  overscan: boolean = false;
+  rotate: number = 0;
+  aspectRatio: number;
 
-  scanline : number;
-  
-  getAudioParams() : SampledAudioParams {
-    return {sampleRate:this.sampleRate, stereo:false};
+  pixels: Uint32Array;
+  audio: SampledAudioSink;
+
+  scanline: number;
+
+  getAudioParams(): SampledAudioParams {
+    return { sampleRate: this.sampleRate, stereo: false };
   }
-  connectAudio(audio : SampledAudioSink) : void {
+  connectAudio(audio: SampledAudioSink): void {
     this.audio = audio;
   }
-  getVideoParams() : VideoParams {
-    return {width:this.canvasWidth,
-           height:this.numVisibleScanlines,
-           aspect:this.aspectRatio,
-           overscan:this.overscan,
-           rotate:this.rotate};
+  getVideoParams(): VideoParams {
+    return {
+      width: this.canvasWidth,
+      height: this.numVisibleScanlines,
+      aspect: this.aspectRatio,
+      overscan: this.overscan,
+      rotate: this.rotate
+    };
   }
-  connectVideo(pixels:Uint32Array) : void {
+  connectVideo(pixels: Uint32Array): void {
     this.pixels = pixels;
   }
 }
 
 export abstract class BasicScanlineMachine extends BasicMachine implements RasterFrameBased {
 
-  abstract numTotalScanlines : number;
-  abstract cpuCyclesPerLine : number;
+  abstract numTotalScanlines: number;
+  abstract cpuCyclesPerLine: number;
 
-  abstract startScanline() : void;
-  abstract drawScanline() : void;
+  abstract startScanline(): void;
+  abstract drawScanline(): void;
 
-  frameCycles : number;
-  
-  advanceFrame(trap: TrapCondition) : number {
+  frameCycles: number;
+
+  advanceFrame(trap: TrapCondition): number {
     this.preFrame();
     var endLineClock = 0;
     var steps = 0;
     this.probe.logNewFrame();
     this.frameCycles = 0;
-    for (var sl=0; sl<this.numTotalScanlines; sl++) {
+    for (var sl = 0; sl < this.numTotalScanlines; sl++) {
       endLineClock += this.cpuCyclesPerLine; // could be fractional
       this.scanline = sl;
       this.startScanline();
diff --git a/src/common/emu.ts b/src/common/emu.ts
index b9db4796..dddda59a 100644
--- a/src/common/emu.ts
+++ b/src/common/emu.ts
@@ -215,6 +215,21 @@ export class VectorVideo extends RasterVideo {
   }
 }
 
+export function drawCrosshair(ctx:CanvasRenderingContext2D, x:number, y:number, width:number) {
+  ctx.fillStyle = 'rgba(0,0,0,0.25)';
+  ctx.fillRect(x-2, 0, 5, 32767);
+  ctx.fillRect(0, y-2, 32767, 5);
+  ctx.lineWidth = width;
+  ctx.strokeStyle = 'rgba(255,255,255,0.75)';
+  ctx.setLineDash([width*2,width*2]);
+  ctx.beginPath();
+  ctx.moveTo(x, 0);
+  ctx.lineTo(x, 32767);
+  ctx.moveTo(0, y);
+  ctx.lineTo(32767, y);
+  ctx.stroke();
+}
+
 export class RAM {
   mem : Uint8Array;
   constructor(size:number) {
diff --git a/src/machine/astrocade.ts b/src/machine/astrocade.ts
index 9e95daae..4078beb1 100644
--- a/src/machine/astrocade.ts
+++ b/src/machine/astrocade.ts
@@ -556,6 +556,7 @@ export class BallyAstrocade extends BasicScanlineMachine implements AcceptsPaddl
       case 'Astro': return this.m.toLongString(state);
     }
   }
+  getRasterCanvasPosition() { return { x: this.getRasterX(), y: this.getRasterY() }; }
 
 }
 
diff --git a/src/machine/atari7800.ts b/src/machine/atari7800.ts
index 306508d1..f9867d96 100644
--- a/src/machine/atari7800.ts
+++ b/src/machine/atari7800.ts
@@ -516,6 +516,7 @@ export class Atari7800 extends BasicMachine implements RasterFrameBased {
     var mc = 0;
     var fc = 0;
     var steps = 0;
+    this.lastFrameCycles = -1;
     this.probe.logNewFrame();
     //console.log(hex(this.cpu.getPC()), hex(this.maria.dll));
     // visible lines
@@ -530,6 +531,7 @@ export class Atari7800 extends BasicMachine implements RasterFrameBased {
         if (trap && trap()) {
           trap = null;
           sl = 999;
+          this.lastFrameCycles = mc;
           break; // TODO?
         }
         mc += this.advanceCPU() << 2;
@@ -567,6 +569,7 @@ export class Atari7800 extends BasicMachine implements RasterFrameBased {
         if (trap && trap()) {
           trap = null;
           sl = 999;
+          this.lastFrameCycles = mc;
           break;
         }
         mc += this.advanceCPU() << 2;
@@ -583,13 +586,18 @@ export class Atari7800 extends BasicMachine implements RasterFrameBased {
       // TODO let bkcol = this.maria.regs[0x0];
       // TODO $(this.video.canvas).css('background-color', COLORS_WEB[bkcol]);
     */
-    this.lastFrameCycles = fc;
     return steps;
   }
 
-  getRasterX() { return this.lastFrameCycles % colorClocksPerLine; }
+  // TODO: doesn't work when breakpoint
+  getRasterX() { return (this.lastFrameCycles + colorClocksPerLine) % colorClocksPerLine; }
+
   getRasterY() { return this.scanline; }
 
+  getRasterCanvasPosition() {
+    return { x: this.getRasterX(), y: this.getRasterY() };
+  }
+
   loadROM(data) {
     if (data.length == 0xc080) data = data.slice(0x80); // strip header
     this.rom = padBytes(data, this.defaultROMSize, true);
diff --git a/src/machine/atari8.ts b/src/machine/atari8.ts
index 83710676..c538a72e 100644
--- a/src/machine/atari8.ts
+++ b/src/machine/atari8.ts
@@ -267,12 +267,18 @@ export class Atari800 extends BasicScanlineMachine implements AcceptsPaddleInput
       keycode: this.keycode,
     };
   }
-  getRasterScanline() {
+  getRasterY() {
     return this.antic.v;
   }
-  getRasterLineClock() {
+  getRasterX() {
     return this.antic.h;
   }
+  getRasterCanvasPosition() {
+    return {
+      x: this.antic.h * 4 - this.firstVisibleClock,
+      y: this.antic.v - this.firstVisibleScanline,
+    }
+  }
   getDebugCategories() {
     return ['CPU', 'Stack', 'ANTIC', 'GTIA', 'POKEY'];
   }
diff --git a/src/machine/c64.ts b/src/machine/c64.ts
index 18adb6bb..82013d13 100644
--- a/src/machine/c64.ts
+++ b/src/machine/c64.ts
@@ -200,9 +200,18 @@ export class C64_WASMMachine extends BaseWASMMachine
     }
     this.exports.c64_joystick(this.sys, this.joymask0, this.joymask1);
   }
+  getRasterX() {
+    return this.statearr[0xf4];
+  }
   getRasterY() {
     return this.exports.machine_get_raster_line(this.sys);
   }
+  getRasterCanvasPosition() {
+    return {
+      x: this.getRasterX() * 392/63,
+      y: this.getRasterY() - 14,
+    }
+  }
   getDebugStateOffset(index: number) {
     var p = this.exports.machine_get_debug_pointer(this.sys, index);
     return p - this.sys;
diff --git a/src/machine/cpc.ts b/src/machine/cpc.ts
index c66be66e..bd175189 100644
--- a/src/machine/cpc.ts
+++ b/src/machine/cpc.ts
@@ -69,6 +69,12 @@ export class CPC_WASMMachine extends BaseWASMMachine implements Machine {
   getRasterY() {
     return this.exports.machine_get_raster_line(this.sys);
   }
+  getRasterCanvasPosition() {
+    return {
+      x: -1, // TODO?
+      y: this.getRasterY() - 14,
+    }
+  }
   /*
     z80_tick_t tick_cb; // 0
     uint64_t bc_de_hl_fa; // 8
diff --git a/src/machine/vic20.ts b/src/machine/vic20.ts
index 465ba4f3..d902e5b6 100644
--- a/src/machine/vic20.ts
+++ b/src/machine/vic20.ts
@@ -93,6 +93,12 @@ export class VIC20_WASMMachine extends BaseWASMMachine implements Machine, Probe
   getRasterY() {
     return this.exports.machine_get_raster_line(this.sys);
   }
+  getRasterCanvasPosition() {
+    return {
+      x: -1, // TODO?
+      y: this.getRasterY() - 14,
+    }
+  }
   getCPUState() {
     this.exports.machine_save_cpu_state(this.sys, this.cpustateptr);
     var s = this.cpustatearr;
diff --git a/src/platform/vcs.ts b/src/platform/vcs.ts
index 8507da1cd..e0851faa 100644
--- a/src/platform/vcs.ts
+++ b/src/platform/vcs.ts
@@ -1,6 +1,6 @@
 
 import { Platform, BasePlatform, cpuStateToLongString_6502, dumpStackToString, DisasmLine, CpuState, getToolForFilename_6502 } from "../common/baseplatform";
-import { PLATFORMS, dumpRAM, EmuHalt, RasterVideo, __createCanvas } from "../common/emu";
+import { PLATFORMS, dumpRAM, EmuHalt, RasterVideo, __createCanvas, drawCrosshair } from "../common/emu";
 import { hex, loadScript, lpad, tobin } from "../common/util";
 import { CodeAnalyzer_vcs } from "../common/analysis";
 import { disassemble6502 } from "../common/cpu/disasm6502";
@@ -72,6 +72,7 @@ function getToolForFilename_vcs(fn: string) {
 class VCSPlatform extends BasePlatform {
 
   lastBreakState; // last breakpoint state
+  canvas : HTMLCanvasElement;
 
   // TODO: super hack for ProbeBitmap view
   machine = {
@@ -92,10 +93,10 @@ class VCSPlatform extends BasePlatform {
     // show console div and start
     $("#javatari-div").show();
     Javatari.start();
-    var console = Javatari.room.console;
+    var jaconsole = Javatari.room.console;
     // intercept clockPulse function
-    console.oldClockPulse = console.clockPulse;
-    console.clockPulse = function() {
+    jaconsole.oldClockPulse = jaconsole.clockPulse;
+    jaconsole.clockPulse = function() {
       self.updateRecorder();
       self.probe.logNewFrame();
       this.oldClockPulse();
@@ -106,18 +107,19 @@ class VCSPlatform extends BasePlatform {
       }
     }
     // intercept TIA end of line
-    var videoSignal = console.tia.getVideoOutput();
+    var videoSignal = jaconsole.tia.getVideoOutput();
     videoSignal.oldNextLine = videoSignal.nextLine;
     videoSignal.nextLine = function(pixels, vsync) {
       self.probe.logNewScanline();
       return this.oldNextLine(pixels, vsync);
     }
     // resize after added to dom tree
-    var jacanvas = $("#javatari-screen").find("canvas");
+    var jacanvas = $("#javatari-screen").find("canvas")[0];
     const resizeObserver = new ResizeObserver(entries => {
       this.resize();
     });
-    resizeObserver.observe(jacanvas[0]);
+    resizeObserver.observe(jacanvas);
+    this.canvas = jacanvas;
   }
 
   loadROM(title, data) {
@@ -148,6 +150,16 @@ class VCSPlatform extends BasePlatform {
   getRasterLineClock() : number {
     return this.getRasterPosition().x;
   }
+  getRasterCanvasPosition() : {x:number,y:number} {
+    let p = Javatari.room.console.tia.getVideoOutput().monitor.getDisplayParameters();
+    let {x,y} = this.getRasterPosition();
+    let canvasPos = {
+      x: (x - p.displayOriginX) * p.displayWidth * p.displayScaleX / (p.signalWidth - p.displayOriginX),
+      y: (y - p.displayOriginY) * p.displayHeight * p.displayScaleY / p.displayHeight
+    };
+    console.log(x,y,canvasPos,p);
+    return canvasPos;
+  }
 
   // TODO: Clock changes this on event, so it may not be current
   isRunning() {
@@ -194,6 +206,8 @@ class VCSPlatform extends BasePlatform {
       Javatari.room.speaker.mute();
       this.lastBreakState = state;
       callback(state);
+      // TODO: we have to delay because javatari timer is still running
+      setTimeout(() => this.updateVideoDebugger(), 100);
     }
     Javatari.room.speaker.mute();
   }
@@ -248,6 +262,7 @@ class VCSPlatform extends BasePlatform {
   }
   readAddress(addr) {
     // TODO: shouldn't have to do this when debugging
+    // TODO: don't read bank switch addresses
     if (this.lastBreakState && addr >= 0x80 && addr < 0x100)
       return this.getRAMForState(this.lastBreakState)[addr & 0x7f];
     else if ((addr & 0x1280) === 0x280)
@@ -419,6 +434,13 @@ class VCSPlatform extends BasePlatform {
     var xt = (1 - scale) * 50;
     $('#javatari-div').css('transform', `translateX(-${xt}%) translateY(-${xt}%) scale(${scale})`);
   }
+  updateVideoDebugger() {
+    const {x,y} = this.getRasterCanvasPosition();
+    if (x >= 0 || y >= 0) {
+      const ctx = this.canvas.getContext('2d');
+      drawCrosshair(ctx, x, y, 2);
+    }
+  }
 };
 
 // TODO: mixin for Base6502Platform?