1 files changed, 74 insertions, 0 deletions
diff --git a/layout/reftests/svg/sizing/svg-image-util.js b/layout/reftests/svg/sizing/svg-image-util.js
new file mode 100644
index 0000000000..d58e622ec7
--- /dev/null
+++ b/layout/reftests/svg/sizing/svg-image-util.js
@@ -0,0 +1,74 @@
+/**
+ * Reusable SVG data uri prefix for generated SVGs.
+ */
+const SVG_DATA_URI_PREFIX = 'data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg"';
+/**
+ * Reusable SVG data uri suffix for generated SVGs.
+ */
+const SVG_DATA_URI_SUFFIX = '><rect fill="brown" x="-2000" y="-2000" width="4000" height="4000"></rect><rect fill="green" height="50" width="50"></rect><rect fill="yellow" x="10" y="10" height="30" width="30"></rect></svg>';
+
+/**
+ * Generates full data URI for an SVG document, with the given parameters
+ * on the SVG element.
+ *
+ * @param aWidth    The width attribute, or null for no width.
+ * @param aHeight   The height attribute, or null for no height.
+ * @param aViewbox  The viewBox attribute, or null for no viewBox.
+ */
+function generateSVGDataURI(aWidth, aHeight, aViewBox) {
+  let datauri = SVG_DATA_URI_PREFIX;
+
+  if (aWidth) {
+    datauri += " width=\"" + aWidth + "\""
+  }
+
+  if (aHeight) {
+    datauri += " height=\"" + aHeight + "\"";
+  }
+
+  if (aViewBox) {
+    datauri += " viewBox=\"" + aViewBox + "\"";
+  }
+
+  datauri += SVG_DATA_URI_SUFFIX;
+
+  return datauri;
+}
+
+/**
+ * Generates a canvas, with the given width and height parameters, and uses
+ * CanvasRenderingContext2D.drawImage() to draw a SVG image with the given
+ * width and height attributes.
+ *
+ * @param aCanvasWidth      The width attribute of the canvas.
+ * @param aCanvasHeight     The height attribute of the canvas.
+ * @param aSVGWidth         The width attribute of the svg, or null for no width.
+ * @param aSVGHeight        The height attribute of the svg, or null for no height.
+ * @param aSVGViewBox       The viewBox attribute sf the svg, or null for no viewBox.
+ *
+ * @returns A promise that resolves when the SVG image has been drawn to the
+ *          created canvas
+ */
+async function generateCanvasDrawImageSVG(aCanvasWidth, aCanvasHeight, aSVGWidth,
+                                          aSVGHeight, aSVGViewBox) {
+    let canvas = document.createElement("canvas");
+    let ctx = canvas.getContext("2d");
+    document.body.appendChild(canvas);
+
+    canvas.setAttribute("width", aCanvasWidth);
+    canvas.setAttribute("height", aCanvasHeight);
+
+    let img = document.createElement("img");
+
+    let promise = new Promise(resolve => {
+      img.onload = () => {
+        ctx.drawImage(img, 0, 0);
+        resolve();
+      };
+    });
+
+    let uri = generateSVGDataURI(aSVGWidth, aSVGHeight, aSVGViewBox);
+    img.src = uri;
+
+    return promise;
+}