modules/canvaskit/tests/core.spec.js

describe('Core canvas behavior', () => {
    let container;

    beforeEach(async () => {
        await LoadCanvasKit;
        container = document.createElement('div');
        container.innerHTML = `
            <canvas width=600 height=600 id=test></canvas>
            <canvas width=600 height=600 id=report></canvas>`;
        document.body.appendChild(container);
    });

    afterEach(() => {
        document.body.removeChild(container);
    });

    gm('picture_test', (canvas) => {
        const spr = new CanvasKit.SkPictureRecorder();
        const rcanvas = spr.beginRecording(
                        CanvasKit.LTRBRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT));
        const paint = new CanvasKit.SkPaint();
        paint.setStrokeWidth(2.0);
        paint.setAntiAlias(true);
        paint.setColor(CanvasKit.Color(0, 0, 0, 1.0));
        paint.setStyle(CanvasKit.PaintStyle.Stroke);

        rcanvas.drawRoundRect(CanvasKit.LTRBRect(5, 35, 45, 80), 15, 10, paint);

        const font = new CanvasKit.SkFont(null, 20);
        rcanvas.drawText('this picture has a round rect', 5, 100, paint, font);
        const pic = spr.finishRecordingAsPicture();
        spr.delete();
        paint.delete();

        canvas.drawPicture(pic);
        pic.delete();
    });

    const uIntColorToCanvasKitColor = (c) => {
        return CanvasKit.Color(
         (c >> 16) & 0xFF,
         (c >>  8) & 0xFF,
         (c >>  0) & 0xFF,
        ((c >> 24) & 0xFF) / 255
      );
    }

    it('can compute tonal colors', () => {
        const input = {
            ambient: CanvasKit.BLUE,
            spot: CanvasKit.RED,
        };
        const out = CanvasKit.computeTonalColors(input);
        expect(new Float32Array(out.ambient)).toEqual(CanvasKit.BLACK);
        const expectedSpot = [0.173, 0, 0, 0.969];
        expect(out.spot[0]).toBeCloseTo(expectedSpot[0], 3);
        expect(out.spot[1]).toBeCloseTo(expectedSpot[1], 3);
        expect(out.spot[2]).toBeCloseTo(expectedSpot[2], 3);
        expect(out.spot[3]).toBeCloseTo(expectedSpot[3], 3);
    });

    // This helper is used for all the MakeImageFromEncoded tests.
    // TODO(kjlubick): rewrite this and callers to use gm
    function decodeAndDrawSingleFrameImage(imgName, goldName, done) {
        const imgPromise = fetch(imgName)
            .then((response) => response.arrayBuffer());
        Promise.all([imgPromise, LoadCanvasKit]).then((values) => {
            const imgData = values[0];
            expect(imgData).toBeTruthy();
            catchException(done, () => {
                let img = CanvasKit.MakeImageFromEncoded(imgData);
                expect(img).toBeTruthy();
                const surface = CanvasKit.MakeCanvasSurface('test');
                expect(surface).toBeTruthy('Could not make surface');
                if (!surface) {
                    done();
                    return;
                }
                const canvas = surface.getCanvas();
                let paint = new CanvasKit.SkPaint();
                canvas.drawImage(img, 0, 0, paint);

                paint.delete();
                img.delete();

                reportSurface(surface, goldName, done);
            })();
        });
    }

    it('can decode and draw a png', (done) => {
        decodeAndDrawSingleFrameImage('/assets/mandrill_512.png', 'drawImage_png', done);
    });

    it('can decode and draw a jpg', (done) => {
        decodeAndDrawSingleFrameImage('/assets/mandrill_h1v1.jpg', 'drawImage_jpg', done);
    });

    it('can decode and draw a (still) gif', (done) => {
        decodeAndDrawSingleFrameImage('/assets/flightAnim.gif', 'drawImage_gif', done);
    });

    it('can decode and draw a still webp', (done) => {
        decodeAndDrawSingleFrameImage('/assets/color_wheel.webp', 'drawImage_webp', done);
    });

   it('can readPixels from an SkImage', (done) => {
        const imgPromise = fetch('/assets/mandrill_512.png')
            .then((response) => response.arrayBuffer());
        Promise.all([imgPromise, LoadCanvasKit]).then((values) => {
            const imgData = values[0];
            expect(imgData).toBeTruthy();
            catchException(done, () => {
                let img = CanvasKit.MakeImageFromEncoded(imgData);
                expect(img).toBeTruthy();
                const imageInfo = {
                    alphaType: CanvasKit.AlphaType.Unpremul,
                    colorType: CanvasKit.ColorType.RGBA_8888,
                    width: img.width(),
                    height: img.height(),
                };

                const pixels = img.readPixels(imageInfo, 0, 0);
                // We know the image is 512 by 512 pixels in size, each pixel
                // requires 4 bytes (R, G, B, A).
                expect(pixels.length).toEqual(512 * 512 * 4);

                img.delete();
                done();
            })();
        });
    });

    gm('drawDrawable_animated_gif', (canvas, fetchedByteBuffers) => {
        let aImg = CanvasKit.MakeAnimatedImageFromEncoded(fetchedByteBuffers[0]);
        expect(aImg).toBeTruthy();
        expect(aImg.getRepetitionCount()).toEqual(-1); // infinite loop
        expect(aImg.width()).toEqual(320);
        expect(aImg.height()).toEqual(240);
        expect(aImg.getFrameCount()).toEqual(60);
        // TODO(kjlubick): deprecate drawAnimatedImage and have it just snap off
        // an SkImage at the desired frame.

        canvas.drawAnimatedImage(aImg, 0, 0);

        let c = aImg.decodeNextFrame();
        expect(c).not.toEqual(-1);
        canvas.drawAnimatedImage(aImg, 300, 0);
        for(let i = 0; i < 10; i++) {
            c = aImg.decodeNextFrame();
            expect(c).not.toEqual(-1);
        }
        canvas.drawAnimatedImage(aImg, 0, 300);
        for(let i = 0; i < 10; i++) {
            c = aImg.decodeNextFrame();
            expect(c).not.toEqual(-1);
        }
        canvas.drawAnimatedImage(aImg, 300, 300);

        aImg.delete();
    }, '/assets/flightAnim.gif');

    gm('1x4_from_scratch', (canvas) => {
        canvas.clear(CanvasKit.WHITE);
        const paint = new CanvasKit.SkPaint();

        // This creates and draws an SkImage that is 1 pixel wide, 4 pixels tall with
        // the colors listed below.
        const pixels = Uint8Array.from([
            255,   0,   0, 255, // opaque red
              0, 255,   0, 255, // opaque green
              0,   0, 255, 255, // opaque blue
            255,   0, 255, 100, // transparent purple
        ]);
        const img = CanvasKit.MakeImage(pixels, 1, 4, CanvasKit.AlphaType.Unpremul, CanvasKit.ColorType.RGBA_8888);
        canvas.drawImage(img, 1, 1, paint);
        img.delete();
    });

    gm('sweep_gradient', (canvas) => {
        const paint = new CanvasKit.SkPaint();
        const shader = CanvasKit.SkShader.MakeSweepGradient(
            100, 100, // X, Y coordinates
            [CanvasKit.GREEN, CanvasKit.BLUE],
            [0.0, 1.0],
            CanvasKit.TileMode.Clamp,
        );
        expect(shader).toBeTruthy('Could not make shader');

        paint.setShader(shader);
        canvas.drawPaint(paint);

        paint.delete();
        shader.delete();
    });

    // TODO(kjlubick): There's a lot of shared code between the gradient gms
    // It would be best to deduplicate that in a nice DAMP way.
    // Inspired by https://fiddle.skia.org/c/b29ce50a341510784ac7d5281586d076
    gm('linear_gradients', (canvas) => {
        canvas.clear(CanvasKit.WHITE);
        canvas.scale(2, 2);
        const strokePaint = new CanvasKit.SkPaint();
        strokePaint.setStyle(CanvasKit.PaintStyle.Stroke);
        strokePaint.setColor(CanvasKit.BLACK);

        const paint = new CanvasKit.SkPaint();
        paint.setStyle(CanvasKit.PaintStyle.Fill);
        const transparentGreen = CanvasKit.Color(0, 255, 255, 0);

        const lgs = CanvasKit.SkShader.MakeLinearGradient(
            [0, 0], [50, 100], // start and stop points
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror
        );
        paint.setShader(lgs);
        let r = CanvasKit.LTRBRect(0, 0, 100, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const lgsPremul = CanvasKit.SkShader.MakeLinearGradient(
            [100, 0], [150, 100], // start and stop points
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            null, // no local matrix
            1 // interpolate colors in premul
        );
        paint.setShader(lgsPremul);
        r = CanvasKit.LTRBRect(100, 0, 200, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const lgs45 = CanvasKit.SkShader.MakeLinearGradient(
            [0, 100], [50, 200], // start and stop points
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.rotated(Math.PI/4, 0, 100),
        );
        paint.setShader(lgs45);
        r = CanvasKit.LTRBRect(0, 100, 100, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const lgs45Premul = CanvasKit.SkShader.MakeLinearGradient(
            [100, 100], [150, 200], // start and stop points
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.rotated(Math.PI/4, 100, 100),
            1 // interpolate colors in premul
        );
        paint.setShader(lgs45Premul);
        r = CanvasKit.LTRBRect(100, 100, 200, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        lgs.delete();
        lgs45.delete();
        lgsPremul.delete();
        lgs45Premul.delete();
        strokePaint.delete();
        paint.delete();
    });

    gm('radial_gradients', (canvas) => {
        canvas.clear(CanvasKit.WHITE);
        canvas.scale(2, 2);
        const strokePaint = new CanvasKit.SkPaint();
        strokePaint.setStyle(CanvasKit.PaintStyle.Stroke);
        strokePaint.setColor(CanvasKit.BLACK);

        const paint = new CanvasKit.SkPaint();
        paint.setStyle(CanvasKit.PaintStyle.Fill);
        const transparentGreen = CanvasKit.Color(0, 255, 255, 0);

        const rgs = CanvasKit.SkShader.MakeRadialGradient(
            [50, 50], 50, // center, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror
        );
        paint.setShader(rgs);
        let r = CanvasKit.LTRBRect(0, 0, 100, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const rgsPremul = CanvasKit.SkShader.MakeRadialGradient(
            [150, 50], 50, // center, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            null, // no local matrix
            1 // interpolate colors in premul
        );
        paint.setShader(rgsPremul);
        r = CanvasKit.LTRBRect(100, 0, 200, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const rgsSkew = CanvasKit.SkShader.MakeRadialGradient(
            [50, 150], 50, // center, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.skewed(0.5, 0, 100, 100)
        );
        paint.setShader(rgsSkew);
        r = CanvasKit.LTRBRect(0, 100, 100, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const rgsSkewPremul = CanvasKit.SkShader.MakeRadialGradient(
            [150, 150], 50, // center, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.skewed(0.5, 0, 100, 100),
            1 // interpolate colors in premul
        );
        paint.setShader(rgsSkewPremul);
        r = CanvasKit.LTRBRect(100, 100, 200, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        rgs.delete();
        rgsPremul.delete();
        rgsSkew.delete();
        rgsSkewPremul.delete();
        strokePaint.delete();
        paint.delete();
    });

    gm('conical_gradients', (canvas) => {
        canvas.clear(CanvasKit.WHITE);
        canvas.scale(2, 2);
        const strokePaint = new CanvasKit.SkPaint();
        strokePaint.setStyle(CanvasKit.PaintStyle.Stroke);
        strokePaint.setColor(CanvasKit.BLACK);

        const paint = new CanvasKit.SkPaint();
        paint.setStyle(CanvasKit.PaintStyle.Fill);
        paint.setAntiAlias(true);
        const transparentGreen = CanvasKit.Color(0, 255, 255, 0);

        const cgs = CanvasKit.SkShader.MakeTwoPointConicalGradient(
            [80, 10], 15, // start, radius
            [10, 110], 60, // end, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror
        );
        paint.setShader(cgs);
        let r = CanvasKit.LTRBRect(0, 0, 100, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const cgsPremul = CanvasKit.SkShader.MakeTwoPointConicalGradient(
            [180, 10], 15, // start, radius
            [110, 110], 60, // end, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            null, // no local matrix
            1, // interpolate colors in premul
        );
        paint.setShader(cgsPremul);
        r = CanvasKit.LTRBRect(100, 0, 200, 100);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const cgs45 = CanvasKit.SkShader.MakeTwoPointConicalGradient(
            [80, 110], 15, // start, radius
            [10, 210], 60, // end, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.rotated(Math.PI/4, 0, 100)
        );
        paint.setShader(cgs45);
        r = CanvasKit.LTRBRect(0, 100, 100, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        const cgs45Premul = CanvasKit.SkShader.MakeTwoPointConicalGradient(
            [180, 110], 15, // start, radius
            [110, 210], 60, // end, radius
            [transparentGreen, CanvasKit.BLUE, CanvasKit.RED],
            [0, 0.65, 1.0],
            CanvasKit.TileMode.Mirror,
            CanvasKit.SkMatrix.rotated(Math.PI/4, 100, 100),
            1 // interpolate colors in premul
        );
        paint.setShader(cgs45Premul);
        r = CanvasKit.LTRBRect(100, 100, 200, 200);
        canvas.drawRect(r, paint);
        canvas.drawRect(r, strokePaint);

        cgs.delete();
        cgsPremul.delete();
        cgs45.delete();
        strokePaint.delete();
        paint.delete();
    });

    gm('blur_filters', (canvas) => {
        const pathUL = starPath(CanvasKit, 100, 100, 80);
        const pathBR = starPath(CanvasKit, 400, 300, 80);
        const paint = new CanvasKit.SkPaint();
        const textFont = new CanvasKit.SkFont(null, 24);

        canvas.drawText('Above: MaskFilter', 20, 220, paint, textFont);
        canvas.drawText('Right: ImageFilter', 20, 260, paint, textFont);

        paint.setColor(CanvasKit.BLUE);

        const blurMask = CanvasKit.SkMaskFilter.MakeBlur(CanvasKit.BlurStyle.Normal, 5, true);
        paint.setMaskFilter(blurMask);
        canvas.drawPath(pathUL, paint);

        const blurIF = CanvasKit.SkImageFilter.MakeBlur(8, 1, CanvasKit.TileMode.Decal, null);
        paint.setImageFilter(blurIF);
        canvas.drawPath(pathBR, paint);

        pathUL.delete();
        pathBR.delete();
        paint.delete();
        blurMask.delete();
        blurIF.delete();
        textFont.delete();
    });

    gm('combined_filters', (canvas, fetchedByteBuffers) => {
        const img = CanvasKit.MakeImageFromEncoded(fetchedByteBuffers[0]);
        expect(img).toBeTruthy();

        canvas.clear(CanvasKit.WHITE);
        const paint = new CanvasKit.SkPaint();
        paint.setAntiAlias(true);
        paint.setColor(CanvasKit.Color(0, 255, 0, 1.0));
        const redCF =  CanvasKit.SkColorFilter.MakeBlend(
                CanvasKit.Color(255, 0, 0, 0.1), CanvasKit.BlendMode.SrcOver);
        const redIF = CanvasKit.SkImageFilter.MakeColorFilter(redCF, null);
        const blurIF = CanvasKit.SkImageFilter.MakeBlur(8, 0.2, CanvasKit.TileMode.Decal, null);
        const combined = CanvasKit.SkImageFilter.MakeCompose(redIF, blurIF);

        // rotate 10 degrees centered on 200, 200
        const m = CanvasKit.SkMatrix.rotated(Math.PI/18, 200, 200);
        const rotated = CanvasKit.SkImageFilter.MakeMatrixTransform(m, CanvasKit.FilterQuality.Medium, combined);
        paint.setImageFilter(rotated);

        //canvas.rotate(10, 200, 200);
        canvas.drawImage(img, 0, 0, paint);
        canvas.drawRect(CanvasKit.LTRBRect(5, 35, 45, 80), paint);

        paint.delete();
        redIF.delete();
        redCF.delete();
        blurIF.delete();
        combined.delete();
        rotated.delete();
        img.delete();
    }, '/assets/mandrill_512.png');

    gm('animated_filters', (canvas, fetchedByteBuffers) => {
        const img = CanvasKit.MakeAnimatedImageFromEncoded(fetchedByteBuffers[0]);
        expect(img).toBeTruthy();
        img.decodeNextFrame();
        img.decodeNextFrame();
        canvas.clear(CanvasKit.WHITE);
        const paint = new CanvasKit.SkPaint();
        paint.setAntiAlias(true);
        paint.setColor(CanvasKit.Color(0, 255, 0, 1.0));
        const redCF =  CanvasKit.SkColorFilter.MakeBlend(
                CanvasKit.Color(255, 0, 0, 0.1), CanvasKit.BlendMode.SrcOver);
        const redIF = CanvasKit.SkImageFilter.MakeColorFilter(redCF, null);
        const blurIF = CanvasKit.SkImageFilter.MakeBlur(8, 0.2, CanvasKit.TileMode.Decal, null);
        const combined = CanvasKit.SkImageFilter.MakeCompose(redIF, blurIF);
        paint.setImageFilter(combined);

        const frame = img.getCurrentFrame();
        canvas.drawImage(frame, 100, 50, paint);

        paint.delete();
        redIF.delete();
        redCF.delete();
        blurIF.delete();
        combined.delete();
        frame.delete();
        img.delete();
    }, '/assets/flightAnim.gif');

    gm('drawImage_skp', (canvas, fetchedByteBuffers) => {
        const pic = CanvasKit.MakeSkPicture(fetchedByteBuffers[0]);
        expect(pic).toBeTruthy();

        canvas.clear(CanvasKit.TRANSPARENT);
        canvas.drawPicture(pic);
    }, '/assets/red_line.skp');

    it('can draw once using drawOnce utility method', (done) => {
        const surface = CanvasKit.MakeCanvasSurface('test');
        expect(surface).toBeTruthy('Could not make surface');
        if (!surface) {
            done();
            return;
        }

        const drawFrame = (canvas) => {
            const paint = new CanvasKit.SkPaint();
            paint.setStrokeWidth(1.0);
            paint.setAntiAlias(true);
            paint.setColor(CanvasKit.Color(0, 0, 0, 1.0));
            paint.setStyle(CanvasKit.PaintStyle.Stroke);
            const path = new CanvasKit.SkPath();
            path.moveTo(20, 5);
            path.lineTo(30, 20);
            path.lineTo(40, 10);
            canvas.drawPath(path, paint);
            path.delete();
            paint.delete();
            // surface hasn't been flushed yet (nor should we call flush
            // ourselves), so reportSurface would likely be blank if we
            // were to call it.
            done();
        }
        surface.drawOnce(drawFrame);
        // Reminder: drawOnce is async. In this test, we are just making
        // sure the drawOnce function is there and doesn't crash, so we can
        // just call done() when the frame is rendered.
    });

    it('can use DecodeCache APIs', () => {
        const initialLimit = CanvasKit.getDecodeCacheLimitBytes();
        expect(initialLimit).toBeGreaterThan(1024 * 1024);

        const newLimit = 42 * 1024 * 1024;
        CanvasKit.setDecodeCacheLimitBytes(newLimit);
        expect(CanvasKit.getDecodeCacheLimitBytes()).toEqual(newLimit);

        // We cannot make any assumptions about this value,
        // so we just make sure it doesn't crash.
        CanvasKit.getDecodeCacheUsedBytes();
    });

    gm('combined_shaders', (canvas) => {
        const rShader = CanvasKit.SkShader.Color(CanvasKit.Color(255, 0, 0, 1.0));
        const gShader = CanvasKit.SkShader.Color(CanvasKit.Color(0, 255, 0, 0.6));
        const bShader = CanvasKit.SkShader.Color(CanvasKit.Color(0, 0, 255, 1.0));

        const rgShader = CanvasKit.SkShader.Blend(CanvasKit.BlendMode.SrcOver, rShader, gShader);

        const p = new CanvasKit.SkPaint();
        p.setShader(rgShader);
        canvas.drawPaint(p);

        const gbShader = CanvasKit.SkShader.Lerp(0.5, gShader, bShader);

        p.setShader(gbShader);
        canvas.drawRect(CanvasKit.LTRBRect(5, 100, 300, 400), p);
        rShader.delete();
        gShader.delete();
        bShader.delete();
        rgShader.delete();
        gbShader.delete();
        p.delete();
    });

    it('exports consts correctly', () => {
        expect(CanvasKit.TRANSPARENT).toEqual(Float32Array.of(0, 0, 0, 0));
        expect(CanvasKit.RED).toEqual(Float32Array.of(1, 0, 0, 1));

        expect(CanvasKit.QUAD_VERB).toEqual(2);
        expect(CanvasKit.CONIC_VERB).toEqual(3);

        expect(CanvasKit.SaveLayerInitWithPrevious).toEqual(4);
        expect(CanvasKit.SaveLayerF16ColorType).toEqual(16);
    });

    it('can set and get a 4f color on a paint', () => {
        const paint = new CanvasKit.SkPaint();
        paint.setColor(CanvasKit.Color4f(3.3, 2.2, 1.1, 0.5));
        expect(paint.getColor()).toEqual(Float32Array.of(3.3, 2.2, 1.1, 0.5));
    });

    describe('DOMMatrix support', () => {
        gm('sweep_gradient_dommatrix', (canvas) => {
            const paint = new CanvasKit.SkPaint();
            const shader = CanvasKit.SkShader.MakeSweepGradient(
                100, 100, // x y coordinates
                [CanvasKit.GREEN, CanvasKit.BLUE],
                [0.0, 1.0],
                CanvasKit.TileMode.Clamp,
                new DOMMatrix().translate(-10, 100),
            );
            expect(shader).toBeTruthy('Could not make shader');
            if (!shader) {
                return;
            }

            paint.setShader(shader);
            canvas.drawPaint(paint);

            paint.delete();
            shader.delete();
        });

        const radiansToDegrees = (rad) => {
           return (rad / Math.PI) * 180;
        }

        // this should draw the same as concat_with4x4_canvas
        gm('concat_dommatrix', (canvas) => {
            const path = starPath(CanvasKit, CANVAS_WIDTH/2, CANVAS_HEIGHT/2);
            const paint = new CanvasKit.SkPaint();
            paint.setAntiAlias(true);
            canvas.clear(CanvasKit.WHITE);
            canvas.concat(new DOMMatrix().translate(CANVAS_WIDTH/2, 0, 0));
            canvas.concat(new DOMMatrix().rotateAxisAngle(1, 0, 0, radiansToDegrees(Math.PI/3)));
            canvas.concat(new DOMMatrix().rotateAxisAngle(0, 1, 0, radiansToDegrees(Math.PI/4)));
            canvas.concat(new DOMMatrix().rotateAxisAngle(0, 0, 1, radiansToDegrees(Math.PI/16)));
            canvas.concat(new DOMMatrix().translate(-CANVAS_WIDTH/2, 0, 0));

            // Draw some stripes to help the eye detect the turn
            const stripeWidth = 10;
            paint.setColor(CanvasKit.BLACK);
            for (let i = 0; i < CANVAS_WIDTH; i += 2*stripeWidth) {
                canvas.drawRect(CanvasKit.LTRBRect(i, 0, i + stripeWidth, CANVAS_HEIGHT), paint);
            }

            paint.setColor(CanvasKit.YELLOW);
            canvas.drawPath(path, paint);
            paint.delete();
            path.delete();
        });
    }); // end describe('DOMMatrix support')

});