Initial touch-action main thread implementation

Source/core/page/EventHandler.cpp

Index: Source/core/page/EventHandler.cpp
diff --git a/Source/core/page/EventHandler.cpp b/Source/core/page/EventHandler.cpp
index 5564a357d61792da3c9cd8f5be7fc3a4d17bd384..a213fef951d150f0c8bcb7b3ec25406d449f7e8b 100644
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -60,6 +60,7 @@
 #include "core/page/AutoscrollController.h"
 #include "core/page/BackForwardClient.h"
 #include "core/page/Chrome.h"
+#include "core/page/ChromeClient.h"
 #include "core/page/DragController.h"
 #include "core/page/DragState.h"
 #include "core/page/EditorClient.h"
@@ -85,6 +86,7 @@
 #include "core/rendering/RenderView.h"
 #include "core/rendering/RenderWidget.h"
 #include "core/rendering/style/CursorList.h"
+#include "core/rendering/style/RenderStyle.h"
 #include "core/svg/SVGDocument.h"
 #include "core/svg/SVGElementInstance.h"
 #include "core/svg/SVGUseElement.h"
@@ -3629,6 +3631,13 @@ bool EventHandler::handleTouchEvent(const PlatformTouchEvent& event)
                 continue;
             m_originatingTouchPointTargets.set(touchPointTargetKey, node);
             touchTarget = node;
+
+            // FIXME(rbyers): Should really be doing a second hit test that ignores inline elements - crbug.com/319479.
+            TouchAction effectiveTouchAction = computeEffectiveTouchAction(node);
+            if (effectiveTouchAction != TouchActionAuto) {
+                m_frame->page()->chrome().client().setTouchAction(point.id(), effectiveTouchAction);
+            }

[abarth-chromium, 2013/11/18 21:16:59]

No need for { }

[Rick Byers, 2013/11/19 21:24:21]

Done.

+
         } else if (pointState == PlatformTouchPoint::TouchReleased || pointState == PlatformTouchPoint::TouchCancelled) {
             // The target should be the original target for this touch, so get it from the hashmap. As it's a release or cancel
             // we also remove it from the map.
@@ -3840,6 +3849,40 @@ bool EventHandler::handleWheelEventAsEmulatedGesture(const PlatformWheelEvent& e
     return true;
 }
 
+TouchAction EventHandler::computeEffectiveTouchAction(Node* node)
+{
+    // Optimization to minimize risk of this new feature (behavior should be identical
+    // since there's no way to get non-default touch-action values).
+    if (!RuntimeEnabledFeatures::cssTouchActionEnabled())
+        return TouchActionAuto;
+
+    // Start by permitting all actions, then walk the block level elements from
+    // the target node up to the nearest scrollable ancestor and exclude any
+    // prohibited actions. For now this is trivial, but when we add more types
+    // of actions it'll get a little more complex.
+    TouchAction effectiveTouchAction = TouchActionAuto;
+
+    while (node) {
+        // The spec says only block and SVG elements get touch-action.
+        // FIXME(rbyers): Add correct support for SVG, crbug.com/247396.
+        if (node->isBlockFlowElement()) {
+            RenderObject* renderer = node->renderer();
+            if (renderer) {

[abarth-chromium, 2013/11/18 21:16:59]

You can combine this line with the previous one.

[Rick Byers, 2013/11/19 21:24:21]

Done.

+                TouchAction action = renderer->style()->touchAction();
+                if (action == TouchActionNone)
+                    effectiveTouchAction = action;
+            }
+        }
+
+        // If we've reached an ancestor that supports a touch action, search no further.
+        if (node->renderBox() && node->renderBox()->scrollsOverflow())
+            break;

[abarth-chromium, 2013/11/18 21:16:59]

I'm not sure if poking the render tree in this way is legit.  We'll need to get
help from some render tree experts.

[Rick Byers, 2013/11/19 21:24:21]

I think this is similar to what scrollNode (here in EventHandler.cpp) does for
mouse wheel and GestureScrollUpdate events - finding the appropriate renderBox
in the render tree and accessing it's state (in that case by calling
RenderBox::calling into it to scroll.  But yes, Elliott, I appreciate any input
you have here.


I think I need to add some iframe test cases though - I might not be handling
them properly (eg. iframes in multi-touch scenarios is already quite
complicated).

+
+        node = node->parentNode();
+    }
+    return effectiveTouchAction;
+}
+
 void EventHandler::setLastKnownMousePosition(const PlatformMouseEvent& event)
 {
     m_mousePositionIsUnknown = false;