Splits SmoothGestureController from RenderWidgetHostImpl

content/browser/renderer_host/smooth_scroll_gesture_controller.cc

+// Copyright (c) 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/smooth_scroll_gesture_controller.h"
+
+#include "base/debug/trace_event.h"
+#include "base/message_loop.h"
+#include "content/common/view_messages.h"
+#include "content/port/browser/render_widget_host_view_port.h"
+#include "content/port/browser/smooth_scroll_gesture.h"
+#include "content/public/browser/render_widget_host.h"
+
+namespace content {
+
+namespace {
+
+// How many milliseconds apart synthetic scroll messages should be sent.
+const int kSyntheticScrollMessageIntervalMs = 8;
+
+}  // namespace
+
+SmoothScrollGestureController::SmoothScrollGestureController()
+    : ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
+      pending_input_event_count_(0),
+      tick_active_smooth_scroll_gestures_task_posted_(false) {
+}
+
+SmoothScrollGestureController::~SmoothScrollGestureController() {
+}
+
+void SmoothScrollGestureController::OnBeginSmoothScroll(
+    RenderWidgetHostViewPort* view, int gesture_id,
+    const ViewHostMsg_BeginSmoothScroll_Params& params) {
+  active_smooth_scroll_gestures_.insert(
+      std::make_pair(gesture_id,
+                     view->CreateSmoothScrollGesture(

[rjkroege, 2013/02/11 22:47:27]

I see that this makes wheel events. Note that wheel scrolling and touch
scrolling are (correctly) diverging and (particularly in main-thread-mediated
scrolling case) have become quite different.

+                         params.scroll_down, params.pixels_to_scroll,
+                         params.mouse_event_x, params.mouse_event_y)));
+
+  // If an input ack is pending, then hold off ticking the gesture
+  // until we get an input ack.
+  if (pending_input_event_count_)
+    return;
+  if (tick_active_smooth_scroll_gestures_task_posted_)
+    return;
+  TickActiveSmoothScrollGesture(view->GetRenderWidgetHost());
+}
+
+void SmoothScrollGestureController::OnForwardInputEvent() {
+  ++pending_input_event_count_;
+}
+
+void SmoothScrollGestureController::OnInputEventACK(RenderWidgetHost* rwh) {
+  --pending_input_event_count_;

[rjkroege, 2013/02/11 22:47:27]

should you verify that this has not gone negative?

+  // If an input ack is pending, then hold off ticking the gesture
+  // until we get an input ack.
+  if (!pending_input_event_count_ && !active_smooth_scroll_gestures_.empty())
+    TickActiveSmoothScrollGesture(rwh);
+}
+
+int SmoothScrollGestureController::SyntheticScrollMessageInterval() const {
+  return kSyntheticScrollMessageIntervalMs;
+}
+
+void SmoothScrollGestureController::TickActiveSmoothScrollGesture(
+    RenderWidgetHost* rwh) {
+  TRACE_EVENT0("input", "RenderWidgetHostImpl::TickActiveSmoothScrollGesture");
+  tick_active_smooth_scroll_gestures_task_posted_ = false;
+  if (active_smooth_scroll_gestures_.empty()) {
+    TRACE_EVENT_INSTANT0("input", "EarlyOut_NoActiveScrollGesture");
+    return;
+  }
+
+  base::TimeTicks now = base::TimeTicks::HighResNow();
+  base::TimeDelta preferred_interval =
+      base::TimeDelta::FromMilliseconds(kSyntheticScrollMessageIntervalMs);
+  base::TimeDelta time_until_next_ideal_interval =
+      (last_smooth_scroll_gestures_tick_time_ + preferred_interval) -
+      now;
+  if (time_until_next_ideal_interval.InMilliseconds() > 0) {
+    TRACE_EVENT_INSTANT1(
+        "input", "EarlyOut_TickedTooRecently",
+        "delay", time_until_next_ideal_interval.InMilliseconds());
+    // Post a task.
+    tick_active_smooth_scroll_gestures_task_posted_ = true;
+    MessageLoop::current()->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(
+            &SmoothScrollGestureController::TickActiveSmoothScrollGesture,
+            weak_factory_.GetWeakPtr(),
+            rwh),
+        time_until_next_ideal_interval);
+    return;
+  }
+
+  last_smooth_scroll_gestures_tick_time_ = now;
+
+  // Separate ticking of gestures from sending their completion messages.
+  std::vector<int> ids_that_are_done;

[rjkroege, 2013/02/11 22:47:27]

possibly dumb question: why do you want to support more than one at a time?

+  for (SmoothScrollGestureMap::iterator it =
+           active_smooth_scroll_gestures_.begin();
+       it != active_smooth_scroll_gestures_.end();
+       ++it) {
+
+    bool active = it->second->ForwardInputEvents(now, rwh);
+    if (!active)
+      ids_that_are_done.push_back(it->first);
+  }
+
+  // Delete completed gestures and send their completion event.
+  for(size_t i = 0; i < ids_that_are_done.size(); i++) {
+    int id = ids_that_are_done[i];
+    SmoothScrollGestureMap::iterator it =
+        active_smooth_scroll_gestures_.find(id);
+    DCHECK(it != active_smooth_scroll_gestures_.end());
+    active_smooth_scroll_gestures_.erase(it);
+
+    rwh->Send(new ViewMsg_SmoothScrollCompleted(rwh->GetRoutingID(), id));
+  }
+
+  // No need to post the next tick if an input is in flight.
+  if (pending_input_event_count_)
+    return;
+
+  TRACE_EVENT_INSTANT1("input", "PostTickTask",
+                       "delay", preferred_interval.InMilliseconds());
+  tick_active_smooth_scroll_gestures_task_posted_ = true;

[rjkroege, 2013/02/11 22:47:27]

it would be nicer to not replicate this chunk of code?

+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&SmoothScrollGestureController::TickActiveSmoothScrollGesture,
+                 weak_factory_.GetWeakPtr(),
+                 rwh),
+      preferred_interval);
+}
+
+}  // namespace content