1 files changed, 90 insertions, 0 deletions
diff --git a/browser/components/newtab/test/browser/browser_getScreenshots.js b/browser/components/newtab/test/browser/browser_getScreenshots.js
new file mode 100644
index 0000000000..6e285c2114
--- /dev/null
+++ b/browser/components/newtab/test/browser/browser_getScreenshots.js
@@ -0,0 +1,90 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// a blue page
+const TEST_URL =
+  "https://example.com/browser/browser/components/newtab/test/browser/blue_page.html";
+const XHTMLNS = "http://www.w3.org/1999/xhtml";
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "Screenshots",
+  "resource://activity-stream/lib/Screenshots.jsm"
+);
+
+function get_pixels(stringOrObject, width, height) {
+  return new Promise(resolve => {
+    // get the pixels out of the screenshot that we just took
+    let img = document.createElementNS(XHTMLNS, "img");
+    let imgPath;
+
+    if (typeof stringOrObject === "string") {
+      Assert.ok(
+        Services.prefs.getBoolPref(
+          "browser.tabs.remote.separatePrivilegedContentProcess"
+        ),
+        "The privileged about content process should be enabled."
+      );
+      imgPath = stringOrObject;
+      Assert.ok(
+        imgPath.startsWith("moz-page-thumb://"),
+        "Thumbnails should be retrieved using moz-page-thumb://"
+      );
+    } else {
+      imgPath = URL.createObjectURL(stringOrObject.data);
+    }
+
+    img.setAttribute("src", imgPath);
+    img.addEventListener(
+      "load",
+      () => {
+        let canvas = document.createElementNS(XHTMLNS, "canvas");
+        canvas.setAttribute("width", width);
+        canvas.setAttribute("height", height);
+        let ctx = canvas.getContext("2d");
+        ctx.drawImage(img, 0, 0, width, height);
+        const result = ctx.getImageData(0, 0, width, height).data;
+        URL.revokeObjectURL(imgPath);
+        resolve(result);
+      },
+      { once: true }
+    );
+  });
+}
+
+add_task(async function test_screenshot() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.pagethumbnails.capturing_disabled", false]],
+  });
+
+  // take a screenshot of a blue page and save it as a blob
+  const screenshotAsObject = await Screenshots.getScreenshotForURL(TEST_URL);
+  let pixels = await get_pixels(screenshotAsObject, 10, 10);
+  let rgbaCount = { r: 0, g: 0, b: 0, a: 0 };
+  while (pixels.length) {
+    // break the pixels into arrays of 4 components [red, green, blue, alpha]
+    let [r, g, b, a, ...rest] = pixels;
+    pixels = rest;
+    // count the number of each coloured pixels
+    if (r === 255) {
+      rgbaCount.r += 1;
+    }
+    if (g === 255) {
+      rgbaCount.g += 1;
+    }
+    if (b === 255) {
+      rgbaCount.b += 1;
+    }
+    if (a === 255) {
+      rgbaCount.a += 1;
+    }
+  }
+
+  // in the end, we should only have 100 blue pixels (10 x 10) with full opacity
+  Assert.equal(rgbaCount.b, 100, "Has 100 blue pixels");
+  Assert.equal(rgbaCount.a, 100, "Has full opacity");
+  Assert.equal(rgbaCount.r, 0, "Does not have any red pixels");
+  Assert.equal(rgbaCount.g, 0, "Does not have any green pixels");
+});