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fix: prevent Alt key stuck error when AltGraph is pressed #181

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fix: prevent Alt key stuck error when AltGraph is pressed #181

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0f391c3
KASM-8279-Update display.js to have dedicated reference to visible ca…
rspruel Apr 12, 2026
758fcba
fix: prevent Alt key stuck error when AltGraph is pressed
ttimonen Apr 15, 2026
d8c727d
Add package-lock.json for Nix build
ttimonen May 16, 2026
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24 changes: 13 additions & 11 deletions core/display.js
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@ export default class Display {
}

this._targetCtx = this._target.getContext('2d');
this._visibleCtx = this._targetCtx; // persistent ref to visible canvas, never reassigned

Log.Debug("User Agent: " + navigator.userAgent);

Expand Down Expand Up @@ -151,21 +152,21 @@ export default class Display {
if (value === this._enableCanvasBuffer) { return; }

this._enableCanvasBuffer = value;
this._targetCtx = value ? this._drawCtx : this._targetCtx;
this._targetCtx = value ? this._drawCtx : this._visibleCtx;

if (value && this._target)
{
//copy current visible canvas to backbuffer
let saveImg = this._targetCtx.getImageData(0, 0, this._target.width, this._target.height);
let saveImg = this._visibleCtx.getImageData(0, 0, this._target.width, this._target.height);
this._drawCtx.putImageData(saveImg, 0, 0);

if (this._transparentOverlayImg) {
this.drawImage(this._transparentOverlayImg, this._transparentOverlayRect.x, this._transparentOverlayRect.y, this._transparentOverlayRect.width, this._transparentOverlayRect.height, true);
}
} else if (!value && this._target) {
//copy backbuffer to canvas to clear any overlays
let saveImg = this._targetCtx.getImageData(0, 0, this._target.width, this._target.height);
this._drawCtx.putImageData(saveImg, 0, 0);
let saveImg = this._drawCtx.getImageData(0, 0, this._target.width, this._target.height);
this._visibleCtx.putImageData(saveImg, 0, 0);
}
}

Expand Down Expand Up @@ -544,7 +545,7 @@ export default class Display {
if (canvas.width !== width || canvas.height !== height) {
let saveImg = null;
if (canvas.width > 0 && canvas.height > 0) {
saveImg = this._targetCtx.getImageData(0, 0, canvas.width, canvas.height);
saveImg = this._visibleCtx.getImageData(0, 0, canvas.width, canvas.height);
}

vp.serverWidth = width;
Expand All @@ -554,7 +555,7 @@ export default class Display {
canvas.height = height;

if (saveImg) {
this._targetCtx.putImageData(saveImg, 0, 0);
this._visibleCtx.putImageData(saveImg, 0, 0);
}

// The position might need to be updated if we've grown
Expand Down Expand Up @@ -673,8 +674,8 @@ export default class Display {
dispose() {
clearInterval(this._frameStatsInterval);
this.clear();
if (this._targetCtx && this._target) {
this._targetCtx.clearRect(0,0, this._target.width, this._target.height);
if (this._visibleCtx && this._target) {
this._visibleCtx.clearRect(0,0, this._target.width, this._target.height);
}
}

Expand Down Expand Up @@ -930,10 +931,11 @@ export default class Display {

drawImage(img, x, y, w, h, overlay=false) {
try {
const ctx = (overlay && this._enableCanvasBuffer) ? this._visibleCtx : this._targetCtx;
if (img.width !== w || img.height !== h) {
this._targetCtx.drawImage(img, x, y, w, h);
ctx.drawImage(img, x, y, w, h);
} else {
this._targetCtx.drawImage(img, x, y);
ctx.drawImage(img, x, y);
}
} catch (error) {
Log.Error('Invalid image received.'); //KASM-2090
Expand Down Expand Up @@ -1002,7 +1004,7 @@ export default class Display {
_writeCtxBuffer() {
//TODO: KASM-5450 Damage tracking with transparent rect overlay support
if (this._backbuffer.width > 0) {
this._targetCtx.drawImage(this._backbuffer, 0, 0);
this._visibleCtx.drawImage(this._backbuffer, 0, 0);
}
}

Expand Down
2 changes: 1 addition & 1 deletion core/input/keyboard.js
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Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ export default class Keyboard {
break;
case "AltLeft":
case "AltRight":
if (!event.altKey) {
if (!event.altKey && !event.key == "AltGraph") {
Log.Error("A alt key is stuck down, sending up. ");
this._sendKeyEvent(value, key, false);
}
Expand Down
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