tav-media/lib/libpag/src/core/global-canvas.js

Cross platform media editing framework

import { DEFAULT_CANVAS_SIZE, WEBGL_CONTEXT_ATTRIBUTES } from '../constant';
import { BackendContext } from './backend-context';
export class GlobalCanvas {
    constructor() {
        this._canvas = null;
        this._glContext = null;
        this.width = DEFAULT_CANVAS_SIZE;
        this.height = DEFAULT_CANVAS_SIZE;
        this.retainCount = 0;
    }
    retain() {
        if (this.retainCount === 0) {
            try {
                this._canvas = new OffscreenCanvas(0, 0);
            }
            catch (error) {
                this._canvas = document.createElement('canvas');
            }
            this._canvas.width = this.width;
            this._canvas.height = this.height;
            const gl = this._canvas.getContext('webgl', WEBGL_CONTEXT_ATTRIBUTES);
            if (!gl)
                throw new Error('Canvas context is not WebGL!');
            this._glContext = BackendContext.from(gl);
        }
        this.retainCount += 1;
    }
    release() {
        this.retainCount -= 1;
        if (this.retainCount === 0) {
            if (!this._glContext)
                return;
            this._glContext.destroy();
            this._glContext = null;
            this._canvas = null;
        }
    }
    get canvas() {
        return this._canvas;
    }
    get glContext() {
        return this._glContext;
    }
    setCanvasSize(width = DEFAULT_CANVAS_SIZE, height = DEFAULT_CANVAS_SIZE) {
        this.width = width;
        this.height = height;
        if (this._glContext && this._canvas) {
            this._canvas.width = width;
            this._canvas.height = height;
        }
    }
}