Make touch-based synthetic gesture take touch slop into account.

content/browser/renderer_host/input/synthetic_pinch_gesture.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/input/synthetic_pinch_gesture.h"
 
 #include <cmath>
 
 #include "content/common/input/input_event.h"
 #include "ui/events/latency_info.h"
 
 namespace content {
-namespace {
-
-// TODO(dominikg): Use touch slop to compute this value.
-const float kMinPointerDistance = 40.0f;
-
-}
 
 SyntheticPinchGesture::SyntheticPinchGesture(
     const SyntheticPinchGestureParams& params)
-    : params_(params), started_(false) {
+    : params_(params),
+      current_y_0_(0),
+      current_y_1_(0),
+      target_y_0_(0),
+      target_y_1_(0),
+      gesture_source_type_(SyntheticGestureParams::DEFAULT_INPUT),
+      state_(SETUP) {
   DCHECK_GE(params_.total_num_pixels_covered, 0);
+}
 
-  float inner_distance_to_anchor = kMinPointerDistance / 2.0f;
-  float outer_distance_to_anchor =
-      inner_distance_to_anchor + params_.total_num_pixels_covered / 2.0f;
+SyntheticPinchGesture::~SyntheticPinchGesture() {}
+
+SyntheticGesture::Result SyntheticPinchGesture::ForwardInputEvents(
+    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+  if (state_ == SETUP) {
+    gesture_source_type_ = params_.gesture_source_type;
+    if (gesture_source_type_ == SyntheticGestureParams::DEFAULT_INPUT)
+      gesture_source_type_ = target->GetDefaultSyntheticGestureSourceType();
+
+    if (!target->SupportsSyntheticGestureSourceType(gesture_source_type_))
+      return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_SUPPORTED_BY_PLATFORM;
+
+    SetupCoordinates(target);
+
+    state_ = STARTED;
+  }
+
+  DCHECK_NE(gesture_source_type_, SyntheticGestureParams::DEFAULT_INPUT);
+  if (gesture_source_type_ == SyntheticGestureParams::TOUCH_INPUT)
+    ForwardTouchInputEvents(interval, target);
+  else
+    return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_IMPLEMENTED;
+
+  return (state_ == DONE) ? SyntheticGesture::GESTURE_FINISHED
+                          : SyntheticGesture::GESTURE_RUNNING;
+}
+
+void SyntheticPinchGesture::ForwardTouchInputEvents(
+    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+  switch (state_) {
+    case STARTED:
+      // Check for an early finish.
+      if (HasReachedTarget()) {
+        state_ = DONE;
+        break;
+      }
+      PressTouchPoints(target);
+      state_ = MOVING;
+      break;
+    case MOVING:
+      UpdateTouchPoints(interval);
+      MoveTouchPoints(target);
+      if (HasReachedTarget()) {
+        ReleaseTouchPoints(target);
+        state_ = DONE;
+      }
+      break;
+    case SETUP:
+      NOTREACHED()
+          << "State SETUP invalid for synthetic pinch.";
+    case DONE:
+      NOTREACHED()
+          << "State DONE invalid for synthetic pinch.";
+  }
+}
+
+void SyntheticPinchGesture::UpdateTouchPoints(base::TimeDelta interval) {
+  // Compute the delta for the first pointer. The other one moves exactly
+  // the same but in the opposite direction.
+  const float delta = GetDeltaForPointer0(interval);
+  current_y_0_ += delta;
+  current_y_1_ -= delta;
+}
+
+void SyntheticPinchGesture::PressTouchPoints(SyntheticGestureTarget* target) {
+  touch_event_.PressPoint(params_.anchor.x(), current_y_0_);
+  touch_event_.PressPoint(params_.anchor.x(), current_y_1_);
+  ForwardTouchEvent(target);
+}
+
+void SyntheticPinchGesture::MoveTouchPoints(SyntheticGestureTarget* target) {
+  // The current pointer positions are stored as float but the pointer
+  // coordinates of the input event are integers. Floor both positions so
+  // that in case of an odd distance one of the pointers (the one whose
+  // position goes down) moves one pixel further than the other. The
+  // explicit flooring is only needed for negative values.
+  touch_event_.MovePoint(0, params_.anchor.x(), floor(current_y_0_));
+  touch_event_.MovePoint(1, params_.anchor.x(), floor(current_y_1_));
+  ForwardTouchEvent(target);
+}
+
+void SyntheticPinchGesture::ReleaseTouchPoints(SyntheticGestureTarget* target) {
+  touch_event_.ReleasePoint(0);
+  touch_event_.ReleasePoint(1);
+  ForwardTouchEvent(target);
+}
+
+void SyntheticPinchGesture::ForwardTouchEvent(SyntheticGestureTarget* target)
+    const {
+  target->DispatchInputEventToPlatform(
+      InputEvent(touch_event_, ui::LatencyInfo(), false));
+}
+
+void SyntheticPinchGesture::SetupCoordinates(SyntheticGestureTarget* target) {
+  DCHECK_EQ(state_, SETUP);
+
+  float inner_distance_to_anchor = 2 * target->GetTouchSlopInDips();
+  float outer_distance_to_anchor = inner_distance_to_anchor +
+                                   params_.total_num_pixels_covered / 2.0f +
+                                   target->GetTouchSlopInDips();
 
   // Move pointers away from each other to zoom in
   // or towards each other to zoom out.
   if (params_.zoom_in) {
     current_y_0_ = params_.anchor.y() - inner_distance_to_anchor;
     current_y_1_ = params_.anchor.y() + inner_distance_to_anchor;
     target_y_0_ = params_.anchor.y() - outer_distance_to_anchor;
     target_y_1_ = params_.anchor.y() + outer_distance_to_anchor;
   } else {
     current_y_0_ = params_.anchor.y() - outer_distance_to_anchor;
     current_y_1_ = params_.anchor.y() + outer_distance_to_anchor;
     target_y_0_ = params_.anchor.y() - inner_distance_to_anchor;
     target_y_1_ = params_.anchor.y() + inner_distance_to_anchor;
   }
 }
 
-SyntheticPinchGesture::~SyntheticPinchGesture() {}
-
-SyntheticGesture::Result SyntheticPinchGesture::ForwardInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
-
-  SyntheticGestureParams::GestureSourceType source =
-      params_.gesture_source_type;
-  if (source == SyntheticGestureParams::DEFAULT_INPUT)
-    source = target->GetDefaultSyntheticGestureSourceType();
-
-  if (!target->SupportsSyntheticGestureSourceType(source))
-    return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_SUPPORTED_BY_PLATFORM;
-
-  if (source == SyntheticGestureParams::TOUCH_INPUT)
-    return ForwardTouchInputEvents(interval, target);
-  else
-    return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_IMPLEMENTED;
-}
-
-SyntheticGesture::Result SyntheticPinchGesture::ForwardTouchInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
-  if (HasFinished())
-    return SyntheticGesture::GESTURE_FINISHED;
-
-  if (!started_) {
-    touch_event_.PressPoint(params_.anchor.x(), current_y_0_);
-    touch_event_.PressPoint(params_.anchor.x(), current_y_1_);
-    ForwardTouchEvent(target);
-    started_ = true;
-  }
-
-  // Compute the delta for the first pointer. The other one moves exactly
-  // the same but in the opposite direction.
-  float delta = GetDeltaForPointer0(interval);
-  current_y_0_ += delta;
-  current_y_1_ -= delta;
-  // The current pointer positions are stored as float but the pointer
-  // coordinates of the input event are integers. Floor both positions so that
-  // in case of an odd distance one of the pointers (the one whose position goes
-  // down) moves one pixel further than the other. The explicit flooring is only
-  // needed for negative values.
-  touch_event_.MovePoint(0, params_.anchor.x(), floor(current_y_0_));
-  touch_event_.MovePoint(1, params_.anchor.x(), floor(current_y_1_));
-  ForwardTouchEvent(target);
-
-  if (HasFinished()) {
-    touch_event_.ReleasePoint(0);
-    touch_event_.ReleasePoint(1);
-    ForwardTouchEvent(target);
-    return SyntheticGesture::GESTURE_FINISHED;
-  }
-
-  return SyntheticGesture::GESTURE_RUNNING;
-}
-
-void SyntheticPinchGesture::ForwardTouchEvent(SyntheticGestureTarget* target) {
-  target->DispatchInputEventToPlatform(
-      InputEvent(touch_event_, ui::LatencyInfo(), false));
-}
-
 float SyntheticPinchGesture::GetDeltaForPointer0(
     const base::TimeDelta& interval) const {
   float total_abs_delta =
       params_.relative_pointer_speed_in_pixels_s * interval.InSecondsF();
 
   // Make sure we're not moving too far in the final step.
   total_abs_delta =
       std::min(total_abs_delta, ComputeAbsoluteRemainingDistance());
 
   float abs_delta_pointer_0 = total_abs_delta / 2;
   return params_.zoom_in ? -abs_delta_pointer_0 : abs_delta_pointer_0;
 }
 
 float SyntheticPinchGesture::ComputeAbsoluteRemainingDistance() const {
   float distance_0 = params_.zoom_in ? (current_y_0_ - target_y_0_)
                                      : (target_y_0_ - current_y_0_);
   DCHECK_GE(distance_0, 0);
 
   // Both pointers move the same overall distance at the same speed.
   return 2 * distance_0;
 }
 
-bool SyntheticPinchGesture::HasFinished() const {
+bool SyntheticPinchGesture::HasReachedTarget() const {
   return ComputeAbsoluteRemainingDistance() == 0;
 }
 
 }  // namespace content