Bug 795567 - Part 2: Introduce ContentHelper class that will be responsible for retrieving touch-action info from content and setting it to widget. r=kats

widget/xpwidgets/ContentHelper.cpp

@@ -0,0 +1,105 @@
+/* -*- 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 "ContentHelper.h"
+#include "nsQueryFrame.h"
+#include "nsIContent.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsStyleConsts.h"
+#include "nsView.h"
+
+namespace mozilla {
+namespace widget {
+
+uint32_t
+ContentHelper::GetTouchActionFromFrame(nsIFrame* aFrame)
+{
+  if (!aFrame || !aFrame->GetContent() || !aFrame->GetContent()->GetPrimaryFrame()) {
+    // If frame is invalid or null then return default value.
+    return NS_STYLE_TOUCH_ACTION_AUTO;
+  }
+
+  if (!aFrame->IsFrameOfType(nsIFrame::eSVG) && !aFrame->IsFrameOfType(nsIFrame::eBlockFrame)) {
+    // Since touch-action property can be applied to only svg and block-level
+    // elements we ignore frames of other types.
+    return NS_STYLE_TOUCH_ACTION_AUTO;
+  }
+
+  return (aFrame->GetContent()->GetPrimaryFrame()->StyleDisplay()->mTouchAction);
+}
+
+void
+ContentHelper::UpdateAllowedBehavior(uint32_t aTouchActionValue, bool aConsiderPanning, TouchBehaviorFlags& aOutBehavior)
+{
+  if (aTouchActionValue != NS_STYLE_TOUCH_ACTION_AUTO) {
+    // Dropping zoom flag since zooming requires touch-action values of all touches
+    // to be AUTO.
+    aOutBehavior &= ~AllowedTouchBehavior::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;
+    }
+  }
+}
+
+ContentHelper::TouchBehaviorFlags
+ContentHelper::GetAllowedTouchBehavior(nsIWidget* aWidget, const nsIntPoint& aPoint)
+{
+  nsView *view = nsView::GetViewFor(aWidget);
+  nsIFrame *viewFrame = view->GetFrame();
+
+  nsPoint relativePoint = nsLayoutUtils::GetEventCoordinatesRelativeTo(aWidget, aPoint, viewFrame);
+
+  nsIFrame *target = nsLayoutUtils::GetFrameForPoint(viewFrame, relativePoint, nsLayoutUtils::IGNORE_ROOT_SCROLL_FRAME);
+  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;
+  TouchBehaviorFlags behavior = AllowedTouchBehavior::VERTICAL_PAN | AllowedTouchBehavior::HORIZONTAL_PAN |
+                                AllowedTouchBehavior::ZOOM;
+
+  for (nsIFrame *frame = target; frame && frame->GetContent() && behavior; frame = frame->GetParent()) {
+    UpdateAllowedBehavior(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;
+}
+
+}
+}

widget/xpwidgets/ContentHelper.h

@@ -0,0 +1,40 @@
+/* -*- 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/. */
+
+#ifndef __mozilla_widget_ContentHelper_h__
+#define __mozilla_widget_ContentHelper_h__
+
+#include "nsIFrame.h"
+#include "nsIWidget.h"
+#include "mozilla/layers/APZCTreeManager.h"
+
+namespace mozilla {
+namespace widget {
+
+/*
+ * Allow different platform widgets to access Content/DOM stuff.
+ */
+class ContentHelper
+{
+  typedef mozilla::layers::AllowedTouchBehavior AllowedTouchBehavior;
+  typedef uint32_t TouchBehaviorFlags;
+
+private:
+  static uint32_t GetTouchActionFromFrame(nsIFrame* aFrame);
+  static void UpdateAllowedBehavior(uint32_t aTouchActionValue, bool aConsiderPanning, TouchBehaviorFlags& aOutBehavior);
+
+public:
+  /*
+   * Performs hit testing on content, finds frame that corresponds to the aPoint and retrieves
+   * touch-action css property value from it according the rules specified in the spec:
+   * http://www.w3.org/TR/pointerevents/#the-touch-action-css-property.
+   */
+  static TouchBehaviorFlags GetAllowedTouchBehavior(nsIWidget* aWidget, const nsIntPoint& aPoint);
+};
+
+}
+}
+
+#endif /*__mozilla_widget_ContentHelper_h__ */

widget/xpwidgets/moz.build

@@ -6,6 +6,7 @@
 
 EXPORTS += [
     'APZCCallbackHelper.h',
+    'ContentHelper.h',
     'GfxDriverInfo.h',
     'GfxInfoBase.h',
     'GfxInfoCollector.h',
@@ -13,6 +14,7 @@ EXPORTS += [
 
 UNIFIED_SOURCES += [
     'APZCCallbackHelper.cpp',
+    'ContentHelper.cpp',
     'GfxDriverInfo.cpp',
     'GfxInfoBase.cpp',
     'GfxInfoCollector.cpp',