Split View Mode: Support for the 2-finger bezel scroll.

athena/wm/bezel_controller.cc

Index: athena/wm/bezel_controller.cc
diff --git a/athena/wm/bezel_controller.cc b/athena/wm/bezel_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0c6247b1826c2896de4bbc5704a3075ffb2f5f29
--- /dev/null
+++ b/athena/wm/bezel_controller.cc
@@ -0,0 +1,168 @@
+// Copyright 2014 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 "athena/wm/bezel_controller.h"
+
+#include "ui/aura/window.h"
+#include "ui/events/event_handler.h"
+
+namespace athena {
+
+// static
+// Using bezel swipes on Nexus 10, the first touch that is registered is
+// usually within 5-10 pixels from the edge, but sometimes as far as 29
+// pixels away. So setting this width fairly high.
+const float BezelController::kBezelWidth = 20.0f;
+
+// static
+const gfx::PointF& BezelController::kScrollPositionNone =
+    gfx::PointF(-100, -100);
+
+BezelController::BezelController(aura::Window* container)
+    : container_(container),
+      num_fingers_down_(0),
+      state_(NO_FINGERS_DOWN),
+      scroll_bezel_(BEZEL_NONE),
+      left_right_delegate_(NULL) {
+}
+
+float BezelController::GetDistance(
+    const gfx::PointF& position, BezelController::Bezel bezel) {
+  DCHECK(bezel == BEZEL_LEFT || bezel == BEZEL_RIGHT);
+  return bezel == BEZEL_LEFT ?
+      position.x() :
+      position.x() - container_->GetBoundsInScreen().width();
+

[Jun Mukai, 2014/07/21 17:18:52]

nit: remove this blank line

[mfomitchev, 2014/07/21 17:31:47]

Done.

+}
+
+void BezelController::SetState(BezelController::State state,
+                               const gfx::PointF& scroll_position) {
+  if (left_right_delegate_) {
+    if (state != state_) {
+      if (state == BEZEL_SCROLLING_TWO_FINGERS) {
+        float delta = GetDistance(scroll_position, scroll_bezel_);
+        left_right_delegate_->ScrollBegin(scroll_bezel_, delta);
+      } else  if (state_ == BEZEL_SCROLLING_TWO_FINGERS) {
+        left_right_delegate_->ScrollEnd();
+      }
+    }
+  }
+  state_ = state;
+  if (state_ == IGNORE || state == NO_FINGERS_DOWN) {
+    scroll_bezel_ = BEZEL_NONE;
+  }
+}
+
+// Only implemented for LEFT and RIGHT bezels ATM.
+BezelController::Bezel BezelController::GetBezel(const gfx::PointF& location) {
+  if (location.x() < kBezelWidth) {
+    return BEZEL_LEFT;
+  } else if (
+      location.x() > container_->GetBoundsInScreen().width() - kBezelWidth) {
+    return BEZEL_RIGHT;
+  } else {
+    return BEZEL_NONE;
+  }
+}
+
+bool BezelController::ShouldProcessGesture(ui::EventType event_type) {
+  return event_type == ui::ET_GESTURE_SCROLL_UPDATE ||
+         event_type == ui::ET_GESTURE_SCROLL_BEGIN ||
+         event_type == ui::ET_GESTURE_BEGIN;
+}
+

[Jun Mukai, 2014/07/21 17:18:52]

nit: remove this blank line

[mfomitchev, 2014/07/21 17:31:47]

Done.

+
+void BezelController::OnTouchEvent(ui::TouchEvent* event) {
+  if (!left_right_delegate_)
+    return;
+
+  // TODO: Currently we aren't retargetting or consuming any of the touch

[Jun Mukai, 2014/07/21 17:18:52]

TODO should have the owner name.
TODO(mfomitchev): ... for example

[mfomitchev, 2014/07/21 17:31:47]

Done.

+  // events. This means that content can prevent the generation of gesture
+  // events and two-finger scroll won't work. Possible solution to this problem
+  // is hosting our own gesture recognizer or retargetting touch events at the
+  // bezel.
+
+  ui::EventType type = event->type();
+  if (type == ui::ET_TOUCH_PRESSED) {
+    num_fingers_down_++;
+    BezelController::Bezel event_bezel =
+        GetBezel(gfx::PointF(event->x(), event->y()));
+
+    if (num_fingers_down_ > 2 ||
+        (event_bezel != BEZEL_LEFT && event_bezel != BEZEL_RIGHT)) {
+      SetState(IGNORE, kScrollPositionNone);
+      return;
+    }
+
+    switch (state_) {
+      case NO_FINGERS_DOWN:
+        SetState(BEZEL_GESTURE_STARTED, kScrollPositionNone);
+        scroll_bezel_ = event_bezel;
+        return;
+      case IGNORE:
+      case BEZEL_GESTURE_STARTED:
+        return;
+      case BEZEL_SCROLLING_ONE_FINGER:
+        if (event_bezel != scroll_bezel_)
+          SetState(IGNORE, kScrollPositionNone);
+        return;
+      case BEZEL_SCROLLING_TWO_FINGERS:
+        // Should've exited above
+        CHECK(false);
+        //NOTREACHED();

[Jun Mukai, 2014/07/21 17:18:52]

I think it's okay to be NOTREACHED(). Anyways, please keep either.

[mfomitchev, 2014/07/21 17:31:47]

Done. Also replaced all CHECKs with DCHECKs - meant to do that before submitting
but forgot.

+        return;
+    };
+  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    num_fingers_down_--;
+    CHECK_NE(state_, NO_FINGERS_DOWN);
+    // The finger beeing lifted gets counted for touch_points.
+    if (num_fingers_down_ == 0) {
+      SetState(NO_FINGERS_DOWN, kScrollPositionNone);
+    } else {
+      // Lifting fingers means the user is doing a gesture other than 2-finger
+      // scrolling.
+      SetState(IGNORE, kScrollPositionNone);
+    }
+    return;

[Jun Mukai, 2014/07/21 17:18:52]

unnecessary to return; Anyways no further code exists.

[mfomitchev, 2014/07/21 17:31:47]

Done.

+  }
+}
+

[Jun Mukai, 2014/07/21 17:18:52]

nit: remove this blank line

[mfomitchev, 2014/07/21 17:31:47]

Done.

+
+void BezelController::OnGestureEvent(ui::GestureEvent* event) {
+  if (!left_right_delegate_)
+    return;
+
+  ui::EventType type = event->type();
+  if (!ShouldProcessGesture(type))
+    return;
+
+  gfx::PointF event_location =  event->location_f();
+  const ui::GestureEventDetails& event_details = event->details();
+
+  if (type == ui::ET_GESTURE_BEGIN &&
+      event_details.touch_points() == 2 &&
+      state_== BEZEL_SCROLLING_ONE_FINGER) {

[Jun Mukai, 2014/07/21 17:18:52]

space between _ and ==

[mfomitchev, 2014/07/21 17:31:47]

Done.

+    SetState(BEZEL_SCROLLING_TWO_FINGERS, event_location);
+  } else if (type == ui::ET_GESTURE_SCROLL_BEGIN) {
+    CHECK(state_ == IGNORE || state_ == BEZEL_GESTURE_STARTED);
+    if (state_ == BEZEL_GESTURE_STARTED) {
+      if (num_fingers_down_ == 1) {
+        SetState(BEZEL_SCROLLING_ONE_FINGER, event_location);
+      } else {
+        CHECK_EQ(num_fingers_down_, 2);
+        SetState(BEZEL_SCROLLING_TWO_FINGERS, event_location);
+        if (left_right_delegate_->CanScroll()) {
+          event->SetHandled();
+          event->StopPropagation();
+        }
+      }
+    }
+    return;

[Jun Mukai, 2014/07/21 17:18:52]

you don't have to return here

[mfomitchev, 2014/07/21 17:31:47]

Done.

+  } else if (type == ui::ET_GESTURE_SCROLL_UPDATE) {
+    float scroll_delta = GetDistance(event_location, scroll_bezel_);
+    left_right_delegate_->ScrollUpdate(scroll_delta);
+  }
+}
+
+}  // namespace athena