Implement CRC2D.scrollPathIntoView() on Canvas

LayoutTests/fast/canvas/script-tests/canvas-scroll-path-into-view.js

+var CShape = function(context, usePathObject) {
+    this._context = context;
+
+    if (usePathObject)
+        this._path = new Path2D();
+    else
+        this._path = context;
+};
+
+CShape.prototype.usePathObject = function() {
+    return this._path instanceof Path2D;
+};
+
+CShape.prototype.createShape = function() {
+    // override
+};
+
+CShape.prototype.draw = function() {
+    var context = this._context;
+    var path = this._path;
+
+    context.beginPath();
+    this.createShape();
+    if (this.usePathObject())
+        context.stroke(path);
+    else
+        context.stroke();
+};
+
+CShape.prototype.scroll = function() {
+    var context = this._context;
+    var path = this._path;
+
+    if (this.usePathObject())
+        context.scrollPathIntoView(path);
+    else
+        context.scrollPathIntoView();
+};
+
+var overrideShape = function(overrideMethod) {
+    var shape = function() {
+        CShape.apply(this, arguments);
+    };
+
+    shape.prototype = new CShape;
+    shape.prototype.createShape = overrideMethod;
+    return shape;
+};
+
+var CRect = overrideShape(function() {
+    var path = this._path;
+
+    path.rect(-50, -50, 100, 100);
+});
+
+var CCapsule = overrideShape(function() {
+    var path = this._path;
+
+    path.arc(-35, 0, 50, Math.PI / 2, Math.PI * 1.5, false);
+    path.lineTo(35, -50);
+    path.arc(50, 0, 50, Math.PI * 1.5, Math.PI / 2, false);
+    path.lineTo(-35, 50);
+});
+
+var CStar = overrideShape(function() {
+    var path = this._path;
+
+    path.moveTo(0, -50);
+    path.lineTo(-15, -10);
+    path.lineTo(-50, -10);
+    path.lineTo(-15, 10);
+    path.lineTo(-35, 50);
+    path.lineTo(0, 20);
+    path.lineTo(35, 50);
+    path.lineTo(15, 10);
+    path.lineTo(50, -10);
+    path.lineTo(15, -10);
+    path.lineTo(0, -50);
+});
+
+var CCurve = overrideShape(function() {
+    var path = this._path;
+
+    path.moveTo(-50, -50);
+    path.bezierCurveTo(-50, 10, 50, 10, 50, 50);
+});
+
+var container = document.querySelector("div[class='container']");
+var canvas = document.querySelector("canvas");
+var context = canvas.getContext("2d");
+
+function getRealValue(shape, degree, usePathObject) {
+    // reset scroll
+    container.scrollTop = 0;
+    container.scrollLeft = 0;
+
+    // draw shape stroke on canvas
+    usePathObject = usePathObject == undefined || usePathObject == null ? false : true;
+    var s = new shape(context, usePathObject);
+
+    context.clearRect(0, 0, 400, 400);
+    context.save();
+    context.translate(200, 200);
+    if (degree != 0 && degree != undefined && degree != null)
+        context.rotate(Math.PI / 180 * degree);
+    s.draw();
+    s.scroll();
+    context.stroke();
+    context.restore();
+
+    return container.scrollTop;
+}
+
+function scrollTest(shape, degree, usePathObject, expectedValue) {
+    var classes = [ "", "border", "padding", "padding border", "margin" ];
+    var offset = [ 0, 500, 500, 1000, 500 ];
+
+    for (var i = 0; i < classes.length; i++) {
+        canvas.className = classes[i];
+        window.testValue = getRealValue(shape, degree, usePathObject);
+        shouldBe("testValue", String(expectedValue + offset[i]));
+    }
+}
+
+description("Series of tests to ensure correct results of scrolling path into view on canvas");
+debug("Test case 1: scrollPathIntoView() / CTM == identity");
+scrollTest(CRect, 0, false, 150);
+scrollTest(CCapsule, 0, false, 150);
+scrollTest(CCurve, 0, false, 150);
+scrollTest(CStar, 0, false, 150);
+debug("");
+
+debug("Test case 2: scrollPathIntoView() / CTM != identity");
+scrollTest(CRect, 20, false, 136);
+scrollTest(CCapsule, 42, false, 126);
+scrollTest(CCurve, 63, false, 133);
+scrollTest(CStar, 40, false, 160);
+debug("");
+
+debug("Test case 3: scrollPathIntoView(path2d) / CTM == identity");
+scrollTest(CRect, 0, true, 150);
+scrollTest(CCapsule, 0, true, 150);
+scrollTest(CCurve, 0, true, 150);
+scrollTest(CStar, 0, true, 150);
+debug("");
+
+debug("Test case 4: scrollPathIntoView(path2d) / CTM != identity");
+scrollTest(CRect, 20, true, 136);
+scrollTest(CCapsule, 42, true, 126);
+scrollTest(CCurve, 63, true, 133);
+scrollTest(CStar, 40, true, 160);
+debug("");
+
+debug("Test case 5: exceptions");
+shouldThrow("context.scrollPathIntoView(null);");
+shouldThrow("context.scrollPathIntoView([]);");
+shouldThrow("context.scrollPathIntoView({});");
+debug("");