Enable pinch-zoom telemetry on Mac

content/browser/renderer_host/input/synthetic_touchpad_pinch_gesture.cc

+// Copyright 2015 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_touchpad_pinch_gesture.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+#include "ui/events/latency_info.h"

[jdduke (slow), 2015/09/22 18:52:37]

Do we need the latency_info include?

[ericrk, 2015/09/22 21:46:26]

nope.

+
+namespace content {
+namespace {
+
+float Lerp(float start, float end, float progress) {
+  return start + progress * (end - start);
+}
+
+}  // namespace
+
+SyntheticTouchpadPinchGesture::SyntheticTouchpadPinchGesture(
+    const SyntheticPinchGestureParams& params)
+    : params_(params),
+      gesture_source_type_(SyntheticGestureParams::DEFAULT_INPUT),
+      state_(SETUP),
+      current_scale_(1.0f) {
+  DCHECK_GT(params_.scale_factor, 0.0f);
+}
+
+SyntheticTouchpadPinchGesture::~SyntheticTouchpadPinchGesture() {}
+
+SyntheticGesture::Result SyntheticTouchpadPinchGesture::ForwardInputEvents(
+    const base::TimeTicks& timestamp,
+    SyntheticGestureTarget* target) {
+  if (state_ == SETUP) {
+    gesture_source_type_ = params_.gesture_source_type;
+    if (gesture_source_type_ == SyntheticGestureParams::DEFAULT_INPUT)
+      gesture_source_type_ = target->GetDefaultSyntheticGestureSourceType();
+
+    state_ = STARTED;
+    start_time_ = timestamp;
+  }
+
+  DCHECK_NE(gesture_source_type_, SyntheticGestureParams::DEFAULT_INPUT);
+  if (gesture_source_type_ == SyntheticGestureParams::MOUSE_INPUT) {
+    ForwardGestureEvents(timestamp, target);
+  } else {
+    // Touch input should be using SyntheticTouchscreenPinchGesture.
+    return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_IMPLEMENTED;
+  }
+
+  return (state_ == DONE) ? SyntheticGesture::GESTURE_FINISHED
+                          : SyntheticGesture::GESTURE_RUNNING;
+}
+
+void SyntheticTouchpadPinchGesture::ForwardGestureEvents(
+    const base::TimeTicks& timestamp,
+    SyntheticGestureTarget* target) {
+  switch (state_) {
+    case STARTED:
+      // Check for an early finish.
+      if (params_.scale_factor == 1.0f) {
+        state_ = DONE;
+        break;
+      }
+
+      CalculateEndTime(target);
+
+      // Send the start event.
+      target->DispatchInputEventToPlatform(
+          SyntheticWebGestureEventBuilder::Build(
+              blink::WebGestureEvent::GesturePinchBegin,
+              blink::WebGestureDeviceTouchpad));
+      state_ = IN_PROGRESS;
+      break;
+    case IN_PROGRESS: {
+      base::TimeTicks event_timestamp = ClampTimestamp(timestamp);
+
+      float target_scale = CalculateTargetScale(event_timestamp);
+      float incremental_scale = target_scale / current_scale_;
+      current_scale_ = target_scale;
+
+      // Send the incremental scale event.
+      target->DispatchInputEventToPlatform(
+          SyntheticWebGestureEventBuilder::BuildPinchUpdate(
+              incremental_scale, params_.anchor.x(), params_.anchor.y(),
+              0 /* modifierFlags */, blink::WebGestureDeviceTouchpad));
+
+      if (HasReachedTarget(event_timestamp)) {
+        target->DispatchInputEventToPlatform(
+            SyntheticWebGestureEventBuilder::Build(
+                blink::WebGestureEvent::GesturePinchEnd,
+                blink::WebGestureDeviceTouchpad));
+        state_ = DONE;
+      }
+      break;
+    }
+    case SETUP:
+      NOTREACHED() << "State SETUP invalid for synthetic pinch.";
+    case DONE:
+      NOTREACHED() << "State DONE invalid for synthetic pinch.";
+  }
+}
+
+float SyntheticTouchpadPinchGesture::CalculateTargetScale(
+    const base::TimeTicks& timestamp) const {
+  // Make sure the final delta is correct. Using the computation below can lead
+  // to issues with floating point precision.
+  if (HasReachedTarget(timestamp))
+    return params_.scale_factor;
+
+  float progress = (timestamp - start_time_).InSecondsF() /
+                   (stop_time_ - start_time_).InSecondsF();
+  return Lerp(1.0f, params_.scale_factor, progress);
+}
+
+// Calculate an end time based on the amount of scaling to be done and the
+// |relative_pointer_speed_in_pixels_s|. Because we don't have an actual pixel
+// delta, we assume that a pinch of 200 pixels is needed to double the screen
+// size and generate a stop time based on that.
+void SyntheticTouchpadPinchGesture::CalculateEndTime(
+    SyntheticGestureTarget* target) {
+  const int kPixelsNeededToDoubleOrHalve = 200;
+
+  float scale_factor = params_.scale_factor;
+  if (scale_factor < 1.0f) {
+    // If we are scaling down, calculate the time based on the inverse so that
+    // halving or doubling the scale takes the same amount of time.
+    scale_factor = 1.0f / scale_factor;
+  }
+  float scale_factor_delta =
+      (scale_factor - 1.0f) * kPixelsNeededToDoubleOrHalve;
+
+  int64 total_duration_in_us =
+      static_cast<int64>(1e6 * (static_cast<double>(scale_factor_delta) /
+                                params_.relative_pointer_speed_in_pixels_s));

[jdduke (slow), 2015/09/22 18:52:37]

Hmm, yeah, this parameter should really have just been a |duration| from the
beginning. Sigh. For now I think it's fine but I think we'll eventually want to
refactor it. I guess there's already a TODO to use a separate set of params,
maybe add another TODO here or at the call site that the scale duration should
be provided?

[ericrk, 2015/09/22 21:46:26]

Done - filed a bug as well.

+  DCHECK_GT(total_duration_in_us, 0);
+  stop_time_ =
+      start_time_ + base::TimeDelta::FromMicroseconds(total_duration_in_us);
+}
+
+base::TimeTicks SyntheticTouchpadPinchGesture::ClampTimestamp(
+    const base::TimeTicks& timestamp) const {
+  return std::min(timestamp, stop_time_);
+}
+
+bool SyntheticTouchpadPinchGesture::HasReachedTarget(
+    const base::TimeTicks& timestamp) const {
+  return timestamp >= stop_time_;
+}
+
+}  // namespace content