UMA stats for stylus usage

ash/common/metrics/pointer_metrics_recorder.cc

+// Copyright 2016 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 "ash/common/metrics/pointer_metrics_recorder.h"
+
+#include "ash/common/wm/maximize_mode/maximize_mode_controller.h"
+#include "ash/common/wm_lookup.h"
+#include "ash/common/wm_shell.h"
+#include "ash/common/wm_window.h"
+#include "ash/shared/app_types.h"
+#include "base/metrics/histogram_macros.h"
+#include "ui/events/event_constants.h"
+#include "ui/views/widget/widget.h"
+
+namespace ash {
+
+namespace {
+
+// Form factor of the down event. This enum is used to back an UMA histogram
+// and should be treated as append-only.

[Daniel Erat, 2016/09/29 22:58:46]

in the interest of correctness, maybe change "should be treated as append-only"
to "new values should be inserted immediately above FORM_FACTOR_COUNT" (ditto
for DownEventSource)

[xiaoyinh(OOO Sep 11-29), 2016/09/30 00:25:39]

Done.

+enum class DownEventFormFactor {
+  CLAMSHELL = 0,
+  TOUCH_VIEW,
+  FORM_FACTOR_COUNT,
+};
+
+// Input type of the down event. This enum is used to back an UMA
+// histogram and should be treated as append-only.
+enum class DownEventSource {
+  UNKNOWN = 0,
+  MOUSE,
+  STYLUS,
+  TOUCH,
+  SOURCE_COUNT,
+};
+
+void RecordUMA(ui::EventPointerType type, views::Widget* target) {
+  DownEventFormFactor form_factor = DownEventFormFactor::CLAMSHELL;
+  if (ash::WmShell::Get()
+          ->maximize_mode_controller()
+          ->IsMaximizeModeWindowManagerEnabled()) {
+    form_factor = DownEventFormFactor::TOUCH_VIEW;
+  }
+  UMA_HISTOGRAM_ENUMERATION(
+      "Event.DownEventCount.PerFormFactor",
+      static_cast<base::HistogramBase::Sample>(form_factor),
+      static_cast<base::HistogramBase::Sample>(
+          DownEventFormFactor::FORM_FACTOR_COUNT));
+
+  DownEventSource input_type = DownEventSource::UNKNOWN;
+  switch (type) {
+    case ui::EventPointerType::POINTER_TYPE_UNKNOWN:
+      input_type = DownEventSource::UNKNOWN;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_MOUSE:
+      input_type = DownEventSource::MOUSE;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_PEN:
+      input_type = DownEventSource::STYLUS;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_TOUCH:
+      input_type = DownEventSource::TOUCH;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_ERASER:
+      input_type = DownEventSource::STYLUS;
+      break;
+  }
+
+  UMA_HISTOGRAM_ENUMERATION(
+      "Event.DownEventCount.PerInput",
+      static_cast<base::HistogramBase::Sample>(input_type),
+      static_cast<base::HistogramBase::Sample>(DownEventSource::SOURCE_COUNT));
+
+  if (!target)

[Daniel Erat, 2016/09/29 22:58:46]

when is this case hit? if it's expected, would it be worthwhile to add a
NO_WINDOW or similar value so that the different counts match?

[xiaoyinh(OOO Sep 11-29), 2016/09/30 00:25:39]

Based on the comments in PointerWatcher, it feels like the target will be null
if it is on mus? I'm going to categorize it as OTHERS, let me know if you think
otherwise.

+    return;
+
+  WmWindow* window = WmLookup::Get()->GetWindowForWidget(target);
+  DCHECK(window);
+
+  UMA_HISTOGRAM_ENUMERATION("Event.DownEventCount.PerDestination",
+                            window->GetAppType(), kAppCount);
+}
+
+}  // namespace
+
+PointerMetricsRecorder::PointerMetricsRecorder() {
+  ash::WmShell::Get()->AddPointerWatcher(
+      this, views::PointerWatcherEventTypes::BASIC);
+}
+
+PointerMetricsRecorder::~PointerMetricsRecorder() {
+  ash::WmShell::Get()->RemovePointerWatcher(this);
+}
+
+void PointerMetricsRecorder::OnPointerEventObserved(
+    const ui::PointerEvent& event,
+    const gfx::Point& location_in_screen,
+    views::Widget* target) {
+  if (event.type() != ui::ET_POINTER_DOWN)

[Daniel Erat, 2016/09/29 22:58:46]

nit: maybe do:

  if (event.type() == ui::ET_POINTER_DOWN)
    RecordUMA(...);

? one fewer line :-P

[xiaoyinh(OOO Sep 11-29), 2016/09/30 00:25:39]

Done.

+    return;
+  RecordUMA(event.pointer_details().pointer_type, target);
+}
+
+}  // namespace ash