Implement support for touch-action: pan-x/pan-y in chromium

content/browser/renderer_host/input/touch_action_filter.cc

Index: content/browser/renderer_host/input/touch_action_filter.cc
diff --git a/content/browser/renderer_host/input/touch_action_filter.cc b/content/browser/renderer_host/input/touch_action_filter.cc
index 665ff15bd30f77441f7d6fc095df4ea6c9cbf071..37fc1e6e5d976afbda28c40e908ce0e834e0cf0e 100644
--- a/content/browser/renderer_host/input/touch_action_filter.cc
+++ b/content/browser/renderer_host/input/touch_action_filter.cc
@@ -4,6 +4,9 @@
 
 #include "content/browser/renderer_host/input/touch_action_filter.h"
 
+#include <math.h>
+
+#include "base/logging.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
 using blink::WebInputEvent;
@@ -16,29 +19,43 @@ TouchActionFilter::TouchActionFilter() :
   allowed_touch_action_(TOUCH_ACTION_AUTO) {
 }
 
-bool TouchActionFilter::FilterGestureEvent(
-    const WebGestureEvent& gesture_event) {
+bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
   // Filter for allowable touch actions first (eg. before the TouchEventQueue
   // can decide to send a touch cancel event).
   // TODO(rbyers): Add touch-action control over for pinch.  crbug.com/247566.
-  switch(gesture_event.type) {
+  switch(gesture_event->type) {
     case WebInputEvent::GestureScrollBegin:
-      if (allowed_touch_action_ == TOUCH_ACTION_NONE)
-        drop_scroll_gesture_events_ = true;
-      // FALL THROUGH
+      DCHECK(!drop_scroll_gesture_events_);
+      drop_scroll_gesture_events_ = ShouldSuppressScroll(*gesture_event);
+      return drop_scroll_gesture_events_;

[jdduke (slow), 2013/12/19 16:17:16]

If a GSB is dropped, the pinch sequence wrapped by the GSB/GSE will fail when it
reaches the impl thread.  As long as we're aware of this  moving forward...

[Rick Byers, 2013/12/19 16:35:09]

Yes, thanks.  As discussed I'll be dropping pinch events whenever scroll events
get dropped, but I'd rather do that in the upcoming pinch-centric CL (see TODO
above).  At the moment nothing outside tests can actually hit this codepath
because the CSSTouchAction RuntimeEnabledFeature in blink is set to 'Test'. 
I'll do some testing on device (including pinch scenarios) before flipping it to
'Experimental' (which will enable it behind a runtime flag).

+
     case WebInputEvent::GestureScrollUpdate:
       if (drop_scroll_gesture_events_)
         return true;
+      else {
+        if (allowed_touch_action_ == TOUCH_ACTION_PAN_X) {
+          gesture_event->data.scrollUpdate.deltaY = 0;
+          gesture_event->data.scrollUpdate.velocityY = 0;
+        } else if (allowed_touch_action_ == TOUCH_ACTION_PAN_Y) {
+          gesture_event->data.scrollUpdate.deltaX = 0;
+          gesture_event->data.scrollUpdate.velocityX = 0;
+        }
+      }
       break;
 
-    case WebInputEvent::GestureScrollEnd:
     case WebInputEvent::GestureFlingStart:
-      allowed_touch_action_ = content::TOUCH_ACTION_AUTO;
-      if (drop_scroll_gesture_events_) {
-        drop_scroll_gesture_events_ = false;
-        return true;
+      if (gesture_event->sourceDevice != WebGestureEvent::Touchscreen)
+        break;
+      if (!drop_scroll_gesture_events_) {
+        if (allowed_touch_action_ == TOUCH_ACTION_PAN_X)
+          gesture_event->data.flingStart.velocityY = 0;
+        if (allowed_touch_action_ == TOUCH_ACTION_PAN_Y)
+          gesture_event->data.flingStart.velocityX = 0;
       }
-      break;
+      return FilterGestureEnd();
+
+    case WebInputEvent::GestureScrollEnd:
+      return FilterGestureEnd();
 
     default:
       // Gesture events unrelated to touch actions (panning/zooming) are left
@@ -49,15 +66,57 @@ bool TouchActionFilter::FilterGestureEvent(
   return false;
 }
 
-void TouchActionFilter::OnSetTouchAction(
-    content::TouchAction touch_action) {
+bool TouchActionFilter::FilterGestureEnd() {
+  allowed_touch_action_ = TOUCH_ACTION_AUTO;
+  if (drop_scroll_gesture_events_) {
+    drop_scroll_gesture_events_ = false;
+    return true;
+  }
+  return false;
+}
+
+void TouchActionFilter::OnSetTouchAction(TouchAction touch_action) {
   // For multiple fingers, we take the intersection of the touch actions for
   // all fingers that have gone down during this action.
   // TODO(rbyers): What exact multi-finger semantic do we want?  This is left
   // as implementation-defined in the pointer events specification.
   // crbug.com/247566.
-  if (touch_action == content::TOUCH_ACTION_NONE)
-    allowed_touch_action_ = content::TOUCH_ACTION_NONE;
+  allowed_touch_action_ = Intersect(allowed_touch_action_, touch_action);
+}
+
+bool TouchActionFilter::ShouldSuppressScroll(
+    const blink::WebGestureEvent& gesture_event) {
+  DCHECK_EQ(gesture_event.type, WebInputEvent::GestureScrollBegin);
+  if (allowed_touch_action_ == TOUCH_ACTION_AUTO)
+    return false;
+  if (allowed_touch_action_ == TOUCH_ACTION_NONE)
+    return true;
+
+  // If there's no hint or it's perfectly diagonal, then allow the scroll.
+  if (fabs(gesture_event.data.scrollBegin.deltaXHint) ==
+      fabs(gesture_event.data.scrollBegin.deltaYHint))
+    return false;
+
+  // Determine the primary initial axis of the scroll, and check whether
+  // panning along that axis is permitted.
+  if (fabs(gesture_event.data.scrollBegin.deltaXHint) >
+      fabs(gesture_event.data.scrollBegin.deltaYHint))
+    return !(allowed_touch_action_ & TOUCH_ACTION_PAN_X);
+  return !(allowed_touch_action_ & TOUCH_ACTION_PAN_Y);
+}
+
+TouchAction TouchActionFilter::Intersect(TouchAction ta1, TouchAction ta2) {
+  if (ta1 == TOUCH_ACTION_NONE || ta2 == TOUCH_ACTION_NONE)
+    return TOUCH_ACTION_NONE;
+  if (ta1 == TOUCH_ACTION_AUTO)
+    return ta2;
+  if (ta2 == TOUCH_ACTION_AUTO)
+    return ta1;
+
+  // Only the true flags are left - take their intersection.
+  if (!(ta1 & ta2))
+    return TOUCH_ACTION_NONE;
+  return static_cast<TouchAction>(ta1 & ta2);
 }
 
 }