1 files changed, 96 insertions, 0 deletions
diff --git a/gfx/layers/apz/util/TouchActionHelper.cpp b/gfx/layers/apz/util/TouchActionHelper.cpp
new file mode 100644
index 0000000000..b35fd2ec7c
--- /dev/null
+++ b/gfx/layers/apz/util/TouchActionHelper.cpp
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "TouchActionHelper.h"
+
+#include "mozilla/layers/APZCTreeManager.h"
+#include "nsContainerFrame.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla {
+namespace layers {
+
+void
+TouchActionHelper::UpdateAllowedBehavior(uint32_t aTouchActionValue,
+                                         bool aConsiderPanning,
+                                         TouchBehaviorFlags& aOutBehavior)
+{
+  if (aTouchActionValue != NS_STYLE_TOUCH_ACTION_AUTO) {
+    // Double-tap-zooming need property value AUTO
+    aOutBehavior &= ~AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
+    if (aTouchActionValue != NS_STYLE_TOUCH_ACTION_MANIPULATION) {
+      // Pinch-zooming need value AUTO or MANIPULATION
+      aOutBehavior &= ~AllowedTouchBehavior::PINCH_ZOOM;
+    }
+  }
+
+  if (aConsiderPanning) {
+    if (aTouchActionValue == NS_STYLE_TOUCH_ACTION_NONE) {
+      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
+      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
+    }
+
+    // Values pan-x and pan-y set at the same time to the same element do not affect panning constraints.
+    // Therefore we need to check whether pan-x is set without pan-y and the same for pan-y.
+    if ((aTouchActionValue & NS_STYLE_TOUCH_ACTION_PAN_X) && !(aTouchActionValue & NS_STYLE_TOUCH_ACTION_PAN_Y)) {
+      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
+    } else if ((aTouchActionValue & NS_STYLE_TOUCH_ACTION_PAN_Y) && !(aTouchActionValue & NS_STYLE_TOUCH_ACTION_PAN_X)) {
+      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
+    }
+  }
+}
+
+TouchBehaviorFlags
+TouchActionHelper::GetAllowedTouchBehavior(nsIWidget* aWidget,
+                                           nsIFrame* aRootFrame,
+                                           const LayoutDeviceIntPoint& aPoint)
+{
+  TouchBehaviorFlags behavior = AllowedTouchBehavior::VERTICAL_PAN | AllowedTouchBehavior::HORIZONTAL_PAN |
+                                AllowedTouchBehavior::PINCH_ZOOM | AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
+
+  nsPoint relativePoint =
+    nsLayoutUtils::GetEventCoordinatesRelativeTo(aWidget, aPoint, aRootFrame);
+
+  nsIFrame *target = nsLayoutUtils::GetFrameForPoint(aRootFrame, relativePoint, nsLayoutUtils::IGNORE_ROOT_SCROLL_FRAME);
+  if (!target) {
+    return behavior;
+  }
+  nsIScrollableFrame *nearestScrollableParent = nsLayoutUtils::GetNearestScrollableFrame(target, 0);
+  nsIFrame* nearestScrollableFrame = do_QueryFrame(nearestScrollableParent);
+
+  // We're walking up the DOM tree until we meet the element with touch behavior and accumulating
+  // touch-action restrictions of all elements in this chain.
+  // The exact quote from the spec, that clarifies more:
+  // To determine the effect of a touch, find the nearest ancestor (starting from the element itself)
+  // that has a default touch behavior. Then examine the touch-action property of each element between
+  // the hit tested element and the element with the default touch behavior (including both the hit
+  // tested element and the element with the default touch behavior). If the touch-action property of
+  // any of those elements disallows the default touch behavior, do nothing. Otherwise allow the element
+  // to start considering the touch for the purposes of executing a default touch behavior.
+
+  // Currently we support only two touch behaviors: panning and zooming.
+  // For panning we walk up until we meet the first scrollable element (the element that supports panning)
+  // or root element.
+  // For zooming we walk up until the root element since Firefox currently supports only zooming of the
+  // root frame but not the subframes.
+
+  bool considerPanning = true;
+
+  for (nsIFrame *frame = target; frame && frame->GetContent() && behavior; frame = frame->GetParent()) {
+    UpdateAllowedBehavior(nsLayoutUtils::GetTouchActionFromFrame(frame), considerPanning, behavior);
+
+    if (frame == nearestScrollableFrame) {
+      // We met the scrollable element, after it we shouldn't consider touch-action
+      // values for the purpose of panning but only for zooming.
+      considerPanning = false;
+    }
+  }
+
+  return behavior;
+}
+
+} // namespace layers
+} // namespace mozilla