1 files changed, 131 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..4598e30a6a
--- /dev/null
+++ b/gfx/layers/apz/util/TouchActionHelper.cpp
@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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 "TouchActionHelper.h"
+
+#include "mozilla/layers/IAPZCTreeManager.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/TouchEvents.h"
+#include "nsContainerFrame.h"
+#include "nsIFrameInlines.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla::layers {
+
+static void UpdateAllowedBehavior(StyleTouchAction aTouchActionValue,
+                                  bool aConsiderPanning,
+                                  TouchBehaviorFlags& aOutBehavior) {
+  if (aTouchActionValue != StyleTouchAction::AUTO) {
+    // Double-tap-zooming need property value AUTO
+    aOutBehavior &= ~AllowedTouchBehavior::ANIMATING_ZOOM;
+    if (aTouchActionValue != StyleTouchAction::MANIPULATION &&
+        !(aTouchActionValue & StyleTouchAction::PINCH_ZOOM)) {
+      // Pinch-zooming needs value AUTO or MANIPULATION, or the PINCH_ZOOM bit
+      // set
+      aOutBehavior &= ~AllowedTouchBehavior::PINCH_ZOOM;
+    }
+  }
+
+  if (aConsiderPanning) {
+    if (aTouchActionValue == StyleTouchAction::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 & StyleTouchAction::PAN_X) &&
+        !(aTouchActionValue & StyleTouchAction::PAN_Y)) {
+      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
+    } else if ((aTouchActionValue & StyleTouchAction::PAN_Y) &&
+               !(aTouchActionValue & StyleTouchAction::PAN_X)) {
+      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
+    }
+  }
+}
+
+static TouchBehaviorFlags GetAllowedTouchBehaviorForPoint(
+    nsIWidget* aWidget, RelativeTo aRootFrame,
+    const LayoutDeviceIntPoint& aPoint) {
+  nsPoint relativePoint =
+      nsLayoutUtils::GetEventCoordinatesRelativeTo(aWidget, aPoint, aRootFrame);
+
+  nsIFrame* target = nsLayoutUtils::GetFrameForPoint(aRootFrame, relativePoint);
+
+  return TouchActionHelper::GetAllowedTouchBehaviorForFrame(target);
+}
+
+nsTArray<TouchBehaviorFlags> TouchActionHelper::GetAllowedTouchBehavior(
+    nsIWidget* aWidget, dom::Document* aDocument,
+    const WidgetTouchEvent& aEvent) {
+  nsTArray<TouchBehaviorFlags> flags;
+  if (!aWidget || !aDocument) {
+    return flags;
+  }
+  if (PresShell* presShell = aDocument->GetPresShell()) {
+    if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
+      for (const auto& touch : aEvent.mTouches) {
+        flags.AppendElement(GetAllowedTouchBehaviorForPoint(
+            aWidget, RelativeTo{rootFrame, ViewportType::Visual},
+            touch->mRefPoint));
+      }
+    }
+  }
+  return flags;
+}
+
+TouchBehaviorFlags TouchActionHelper::GetAllowedTouchBehaviorForFrame(
+    nsIFrame* aFrame) {
+  TouchBehaviorFlags behavior = AllowedTouchBehavior::VERTICAL_PAN |
+                                AllowedTouchBehavior::HORIZONTAL_PAN |
+                                AllowedTouchBehavior::PINCH_ZOOM |
+                                AllowedTouchBehavior::ANIMATING_ZOOM;
+
+  if (!aFrame) {
+    return behavior;
+  }
+
+  nsIScrollableFrame* nearestScrollableParent =
+      nsLayoutUtils::GetNearestScrollableFrame(aFrame, 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 = aFrame; frame && frame->GetContent() && behavior;
+       frame = frame->GetInFlowParent()) {
+    UpdateAllowedBehavior(frame->UsedTouchAction(), 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 mozilla::layers