1 files changed, 53 insertions, 0 deletions
diff --git a/gfx/layers/apz/test/mochitest/helper_fullscreen.html b/gfx/layers/apz/test/mochitest/helper_fullscreen.html
new file mode 100644
index 0000000000..32de4979f2
--- /dev/null
+++ b/gfx/layers/apz/test/mochitest/helper_fullscreen.html
@@ -0,0 +1,53 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width; initial-scale=1.0">
+  <title>Tests that layout viewport is not larger than visual viewport on fullscreen</title>
+  <script type="application/javascript" src="apz_test_utils.js"></script>
+  <script src="/tests/SimpleTest/paint_listener.js"></script>
+  <style>
+    body {
+      margin: 0;
+      padding: 0;
+      overflow-x: hidden;
+    }
+  </style>
+</head>
+<body>
+  <div style="background: blue; width: 100%; height: 100%;"></div>
+  <div style="background: red; width: 200%; height: 100px;">overflowed element</div>
+  <div id="target" style="background: green; width: 100px; height: 100px;"></div>
+  <script type="application/javascript">
+    const utils = SpecialPowers.getDOMWindowUtils(window);
+
+    function waitForFullscreenChange() {
+      return new Promise(resolve => {
+        document.addEventListener("fullscreenchange", resolve);
+      });
+    }
+
+    async function test(testDriver) {
+      target.requestFullscreen();
+
+      await waitForFullscreenChange();
+
+      is(document.fullscreenElement, target,
+         "The target element should have been fullscreen-ed");
+
+      // Try to move rightward, but it should NOT happen.
+      utils.scrollToVisual(200, 0, utils.UPDATE_TYPE_MAIN_THREAD,
+                           utils.SCROLL_MODE_INSTANT);
+
+      await waitUntilApzStable();
+
+      is(visualViewport.offsetLeft, 0,
+         "The visual viewport offset should never be moved");
+
+      document.exitFullscreen();
+    }
+
+    waitUntilApzStable().then(test).then(subtestDone, subtestFailed);
+  </script>
+</body>
+</html>