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Handle WebGL context loss/restore events in WebGL renderer. #4075

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merged 2 commits into from
Aug 31, 2022
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Handle WebGL context loss/restore events in WebGL renderer. #4075

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9459553
Handle WebGL context loss/restore events in WebGL renderer.
kenrussell Aug 26, 2022
f309aff
Tweak handling of _contextRestorationTimeout
Tyriar Aug 31, 2022
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50 changes: 42 additions & 8 deletions addons/xterm-addon-webgl/src/WebglRenderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -46,13 +46,14 @@ export class WebglRenderer extends Disposable implements IRenderer {

private _canvas: HTMLCanvasElement;
private _gl: IWebGL2RenderingContext;
private _rectangleRenderer: RectangleRenderer;
private _glyphRenderer: GlyphRenderer;
private _rectangleRenderer!: RectangleRenderer;
private _glyphRenderer!: GlyphRenderer;

public dimensions: IRenderDimensions;

private _core: ITerminal;
private _isAttached: boolean;
private _contextRestorationTimeout: number | undefined;

private _onChangeTextureAtlas = new EventEmitter<HTMLCanvasElement>();
public get onChangeTextureAtlas(): IEvent<HTMLCanvasElement> { return this._onChangeTextureAtlas.event; }
Expand Down Expand Up @@ -108,16 +109,34 @@ export class WebglRenderer extends Disposable implements IRenderer {
throw new Error('WebGL2 not supported ' + this._gl);
}

this.register(addDisposableDomListener(this._canvas, 'webglcontextlost', (e) => { this._onContextLoss.fire(e); }));
this.register(addDisposableDomListener(this._canvas, 'webglcontextlost', (e) => {
console.log('webglcontextlost event received');
// Prevent the default behavior in order to enable WebGL context restoration.
e.preventDefault();
// Wait a few seconds to see if the 'webglcontextrestored' event is fired.
// If not, dispatch the onContextLoss notification to observers.
this._contextRestorationTimeout = setTimeout(() => {
this._contextRestorationTimeout = undefined;
console.warn('webgl context not restored; firing onContextLoss');
this._onContextLoss.fire(e);
}, 3000 /* ms */);
}));
this.register(addDisposableDomListener(this._canvas, 'webglcontextrestored', (e) => {
console.warn('webglcontextrestored event received');
clearTimeout(this._contextRestorationTimeout);
this._contextRestorationTimeout = undefined;
// The texture atlas and glyph renderer must be fully reinitialized
// because their contents have been lost.
removeTerminalFromCache(this._terminal);
this._initializeWebGLState();
this._requestRedrawViewport();
}));

this.register(observeDevicePixelDimensions(this._canvas, (w, h) => this._setCanvasDevicePixelDimensions(w, h)));

this._core.screenElement!.appendChild(this._canvas);

this._rectangleRenderer = this.register(new RectangleRenderer(this._terminal, this._colors, this._gl, this.dimensions));
this._glyphRenderer = this.register(new GlyphRenderer(this._terminal, this._colors, this._gl, this.dimensions));

// Update dimensions and acquire char atlas
this.onCharSizeChanged();
this._initializeWebGLState();

this._isAttached = document.body.contains(this._core.screenElement!);
}
Expand Down Expand Up @@ -235,6 +254,21 @@ export class WebglRenderer extends Disposable implements IRenderer {
this._refreshCharAtlas();
}

/**
* Initializes members dependent on WebGL context state.
*/
private _initializeWebGLState(): void {
// Dispose any previous rectangle and glyph renderers before creating new ones.
this._rectangleRenderer?.dispose();
this._glyphRenderer?.dispose();

this._rectangleRenderer = new RectangleRenderer(this._terminal, this._colors, this._gl, this.dimensions);
this._glyphRenderer = new GlyphRenderer(this._terminal, this._colors, this._gl, this.dimensions);
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// Update dimensions and acquire char atlas
this.onCharSizeChanged();
}

/**
* Refreshes the char atlas, aquiring a new one if necessary.
* @param terminal The terminal.
Expand Down
2 changes: 1 addition & 1 deletion demo/client.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -606,7 +606,7 @@ function htmlSerializeButtonHandler(): void {
}

function addTextureAtlas(e: HTMLCanvasElement) {
document.querySelector('#texture-atlas').appendChild(e);
document.querySelector('#texture-atlas').replaceChildren(e);
}

function writeCustomGlyphHandler() {
Expand Down