1 files changed, 64 insertions, 0 deletions
diff --git a/gfx/layers/apz/test/gtest/TestSnapping.cpp b/gfx/layers/apz/test/gtest/TestSnapping.cpp
new file mode 100644
index 000000000..95c21ca44
--- /dev/null
+++ b/gfx/layers/apz/test/gtest/TestSnapping.cpp
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et tw=80 : */
+/* 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/. */
+
+#include "APZCTreeManagerTester.h"
+#include "APZTestCommon.h"
+#include "InputUtils.h"
+
+class APZCSnappingTester : public APZCTreeManagerTester
+{
+};
+
+TEST_F(APZCSnappingTester, Bug1265510)
+{
+  const char* layerTreeSyntax = "c(t)";
+  nsIntRegion layerVisibleRegion[] = {
+    nsIntRegion(IntRect(0, 0, 100, 100)),
+    nsIntRegion(IntRect(0, 100, 100, 100))
+  };
+  root = CreateLayerTree(layerTreeSyntax, layerVisibleRegion, nullptr, lm, layers);
+  SetScrollableFrameMetrics(root, FrameMetrics::START_SCROLL_ID, CSSRect(0, 0, 100, 200));
+  SetScrollableFrameMetrics(layers[1], FrameMetrics::START_SCROLL_ID + 1, CSSRect(0, 0, 100, 200));
+  SetScrollHandoff(layers[1], root);
+
+  ScrollSnapInfo snap;
+  snap.mScrollSnapTypeY = NS_STYLE_SCROLL_SNAP_TYPE_MANDATORY;
+  snap.mScrollSnapIntervalY = Some(100 * AppUnitsPerCSSPixel());
+
+  ScrollMetadata metadata = root->GetScrollMetadata(0);
+  metadata.SetSnapInfo(ScrollSnapInfo(snap));
+  root->SetScrollMetadata(metadata);
+
+  UniquePtr<ScopedLayerTreeRegistration> registration = MakeUnique<ScopedLayerTreeRegistration>(manager, 0, root, mcc);
+  manager->UpdateHitTestingTree(0, root, false, 0, 0);
+
+  TestAsyncPanZoomController* outer = ApzcOf(layers[0]);
+  TestAsyncPanZoomController* inner = ApzcOf(layers[1]);
+
+  // Position the mouse near the bottom of the outer frame and scroll by 60px.
+  // (6 lines of 10px each). APZC will actually scroll to y=100 because of the
+  // mandatory snap coordinate there.
+  TimeStamp now = mcc->Time();
+  SmoothWheel(manager, ScreenIntPoint(50, 80), ScreenPoint(0, 6), now);
+  // Advance in 5ms increments until we've scrolled by 70px. At this point, the
+  // closest snap point is y=100, and the inner frame should be under the mouse
+  // cursor.
+  while (outer->GetCurrentAsyncScrollOffset(AsyncPanZoomController::AsyncMode::NORMAL).y < 70) {
+    mcc->AdvanceByMillis(5);
+    outer->AdvanceAnimations(mcc->Time());
+  }
+  // Now do another wheel in a new transaction. This should start scrolling the
+  // inner frame; we verify that it does by checking the inner scroll position.
+  TimeStamp newTransactionTime = now + TimeDuration::FromMilliseconds(gfxPrefs::MouseWheelTransactionTimeoutMs() + 100);
+  SmoothWheel(manager, ScreenIntPoint(50, 80), ScreenPoint(0, 6), newTransactionTime);
+  inner->AdvanceAnimationsUntilEnd();
+  EXPECT_LT(0.0f, inner->GetCurrentAsyncScrollOffset(AsyncPanZoomController::AsyncMode::NORMAL).y);
+
+  // However, the outer frame should also continue to the snap point, otherwise
+  // it is demonstrating incorrect behaviour by violating the mandatory snapping.
+  outer->AdvanceAnimationsUntilEnd();
+  EXPECT_EQ(100.0f, outer->GetCurrentAsyncScrollOffset(AsyncPanZoomController::AsyncMode::NORMAL).y);
+}