Support longpress drag selection

ui/touch_selection/touch_selection_controller.h

Index: ui/touch_selection/touch_selection_controller.h
diff --git a/ui/touch_selection/touch_selection_controller.h b/ui/touch_selection/touch_selection_controller.h
index 115dd0d637046b44aa49c42e832fc5e82489cc95..423c966a2396f0f52b668f360531e596a5609cae 100644
--- a/ui/touch_selection/touch_selection_controller.h
+++ b/ui/touch_selection/touch_selection_controller.h
@@ -8,6 +8,7 @@
 #include "ui/base/touch/selection_bound.h"
 #include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/rect_f.h"
+#include "ui/gfx/geometry/vector2d_f.h"
 #include "ui/touch_selection/selection_event_type.h"
 #include "ui/touch_selection/touch_handle.h"
 #include "ui/touch_selection/touch_handle_orientation.h"
@@ -59,7 +60,7 @@ class UI_TOUCH_SELECTION_EXPORT TouchSelectionController
 
   // To be called before forwarding a longpress event. This allows automatically
   // showing the selection or insertion handles from subsequent bounds changes.
-  void OnLongPressEvent();
+  void OnLongPressEvent(const gfx::PointF& location);
 
   // Allow showing the selection handles from the most recent selection bounds
   // update (if valid), or a future valid bounds update.
@@ -123,6 +124,10 @@ class UI_TOUCH_SELECTION_EXPORT TouchSelectionController
   void DeactivateSelection();
   void ResetCachedValuesIfInactive();
 
+  bool WillHandleTouchEventForLongPressDrag(const MotionEvent& event);
+  void SetTemporarilyHiddenForLongPressDrag(bool hidden);
+  void OnHandleVisibilityOverrideChanged();
+
   gfx::Vector2dF GetStartLineOffset() const;
   gfx::Vector2dF GetEndLineOffset() const;
   bool GetStartVisible() const;
@@ -160,6 +165,18 @@ class UI_TOUCH_SELECTION_EXPORT TouchSelectionController
 
   bool temporarily_hidden_;
 
+  // Longpress drag allows direct manipulation of longpress-initiated selection.
+  // TODO(jdduke): Factor out longpress drag-specific logic into a more isolated

[mfomitchev, 2015/04/18 16:09:08]

I wonder if we can reuse some of the TouchHandle code for this. The 'long press
logic unit' seems somewhat similar to the TouchHandle in the way it interacts
with TSC. Perhaps we can factor out the common functionality in a superclass
(TouchSelectionEventProcessor)? 
- The long press logic unit would either extend this superclass or use it
directly. 
- TouchHandle would extend it. 
- TSC would interact with the handles and the long press logic unit through this
superclass's interfact (i.e. the instance of start_selection_handle_ would be
TouchSelectionEventProcessor). 
- TouchHandleClient would become TouchSelectionEventProcessorClient

Then instead of calling WillHandleTouchEventForLongPressDrag(event), we'd just
call longpress_drag_processor_->WillHandleTouchEvent(event), same way we do for
handles. Instead of storing temporarily_hidden_for_longpress_drag_, we'd just
check longpress_drag_processor_->is_dragging(), etc. Do you think something like
this would work? 

[jdduke (slow), 2015/04/21 19:25:57]

I think this is very reasonable. I'd been planning to also pull the
|StylusSelectionController| into this class and have it serve a similar function
(i.e., delegate to it touch events, have it manipulate the selection as a
side-effect). I'll see if I can tease out a simple/common interface, not sure if
we need to force both the handles/drag processing through identical interface,
but I think sharing logic would be beneficial.

[mfomitchev, 2015/04/21 21:08:57]

Do you mean StylusTextSelector?

+  // logic unit.
+  bool temporarily_hidden_for_longpress_drag_;

[mfomitchev, 2015/04/18 16:09:08]

handles_hidden_for_longpress_drag_? Otherwise it's not clear what's hidden.Same
with the setter.

[jdduke (slow), 2015/04/21 19:25:57]

Hmm, well this is a parallel of the existing |temporarily_hidden_| flag, which I
guess is also somewhat ambiguous. I'll update.

+  bool consume_remaining_motion_for_longpress_drag_;
+  bool has_begun_longpress_drag_;
+  gfx::PointF longpress_drag_initial_position_;
+  gfx::Vector2dF longpress_drag_selection_offset_;
+
+  bool has_active_touch_sequence_;
+  gfx::PointF touch_sequence_start_position_;
+
   base::TimeTicks selection_start_time_;
   // Whether a selection handle was dragged during the current 'selection
   // session' - i.e. since the current selection has been activated.