Update the signature of the PageViewport constructor, and improve the JSDoc comments for the class

This changes the constructor to take a parameter object, rather than a string of parameters.

src/display/api.js

@@ -885,7 +885,12 @@ var PDFPageProxy = (function PDFPageProxyClosure() {
      * along with transforms required for rendering.
      */
     getViewport(scale, rotate = this.rotate, dontFlip = false) {
-      return new PageViewport(this.view, scale, rotate, 0, 0, dontFlip);
+      return new PageViewport({
+        viewBox: this.view,
+        scale,
+        rotation: rotate,
+        dontFlip,
+      });
     },
     /**
      * @param {GetAnnotationsParameters} params - Annotation parameters.

src/display/dom_utils.js

@@ -135,19 +135,38 @@ class DOMSVGFactory {
   }
 }
 
+/**
+ * @typedef {Object} PageViewportParameters
+ * @property {Array} viewBox - The xMin, yMin, xMax and yMax coordinates.
+ * @property {number} scale - The scale of the viewport.
+ * @property {number} rotation - The rotation, in degrees, of the viewport.
+ * @property {number} offsetX - (optional) The vertical, i.e. x-axis, offset.
+ *   The default value is `0`.
+ * @property {number} offsetY - (optional) The horizontal, i.e. y-axis, offset.
+ *   The default value is `0`.
+ * @property {boolean} dontFlip - (optional) If true, the x-axis will not be
+ *   flipped. The default value is `false`.
+ */
+
+/**
+ * @typedef {Object} PageViewportCloneParameters
+ * @property {number} scale - (optional) The scale, overriding the one in the
+ *   cloned viewport. The default value is `this.scale`.
+ * @property {number} rotation - (optional) The rotation, in degrees, overriding
+ *   the one in the cloned viewport. The default value is `this.rotation`.
+ * @property {boolean} dontFlip - (optional) If true, the x-axis will not be
+ *   flipped. The default value is `false`.
+ */
+
 /**
  * PDF page viewport created based on scale, rotation and offset.
  */
 class PageViewport {
   /**
-   * @param viewBox {Array} xMin, yMin, xMax and yMax coordinates.
-   * @param scale {number} scale of the viewport.
-   * @param rotation {number} rotations of the viewport in degrees.
-   * @param offsetX {number} offset X
-   * @param offsetY {number} offset Y
-   * @param dontFlip {boolean} if true, axis Y will not be flipped.
+   * @param {PageViewportParameters}
    */
-  constructor(viewBox, scale, rotation, offsetX, offsetY, dontFlip) {
+  constructor({ viewBox, scale, rotation, offsetX = 0, offsetY = 0,
+                dontFlip = false, }) {
     this.viewBox = viewBox;
     this.scale = scale;
     this.rotation = rotation;
@@ -211,27 +230,29 @@ class PageViewport {
   }
 
   /**
-   * Clones viewport with additional properties.
-   * @param args {Object} (optional) If specified, may contain the 'scale' or
-   * 'rotation' properties to override the corresponding properties in
-   * the cloned viewport.
-   * @returns {PageViewport} Cloned viewport.
+   * Clones viewport, with optional additional properties.
+   * @param {PageViewportCloneParameters} - (optional)
+   * @return {PageViewport} Cloned viewport.
    */
-  clone(args) {
-    args = args || {};
-    let scale = 'scale' in args ? args.scale : this.scale;
-    let rotation = 'rotation' in args ? args.rotation : this.rotation;
-    return new PageViewport(this.viewBox.slice(), scale, rotation,
-                            this.offsetX, this.offsetY, args.dontFlip);
+  clone({ scale = this.scale, rotation = this.rotation,
+          dontFlip = false, } = {}) {
+    return new PageViewport({
+      viewBox: this.viewBox.slice(),
+      scale,
+      rotation,
+      offsetX: this.offsetX,
+      offsetY: this.offsetY,
+      dontFlip,
+    });
   }
 
   /**
    * Converts PDF point to the viewport coordinates. For examples, useful for
    * converting PDF location into canvas pixel coordinates.
-   * @param x {number} X coordinate.
-   * @param y {number} Y coordinate.
-   * @returns {Object} Object that contains 'x' and 'y' properties of the
-   * point in the viewport coordinate space.
+   * @param {number} x - The x-coordinate.
+   * @param {number} y - The y-coordinate.
+   * @return {Object} Object containing `x` and `y` properties of the
+   *   point in the viewport coordinate space.
    * @see {@link convertToPdfPoint}
    * @see {@link convertToViewportRectangle}
    */
@@ -241,9 +262,9 @@ class PageViewport {
 
   /**
    * Converts PDF rectangle to the viewport coordinates.
-   * @param rect {Array} xMin, yMin, xMax and yMax coordinates.
-   * @returns {Array} Contains corresponding coordinates of the rectangle
-   * in the viewport coordinate space.
+   * @param {Array} rect - The xMin, yMin, xMax and yMax coordinates.
+   * @return {Array} Array containing corresponding coordinates of the rectangle
+   *   in the viewport coordinate space.
    * @see {@link convertToViewportPoint}
    */
   convertToViewportRectangle(rect) {
@@ -255,10 +276,10 @@ class PageViewport {
   /**
    * Converts viewport coordinates to the PDF location. For examples, useful
    * for converting canvas pixel location into PDF one.
-   * @param x {number} X coordinate.
-   * @param y {number} Y coordinate.
-   * @returns {Object} Object that contains 'x' and 'y' properties of the
-   * point in the PDF coordinate space.
+   * @param {number} x - The x-coordinate.
+   * @param {number} y - The y-coordinate.
+   * @return {Object} Object containing `x` and `y` properties of the
+   *   point in the PDF coordinate space.
    * @see {@link convertToViewportPoint}
    */
   convertToPdfPoint(x, y) {