Use platform slop/timeout values for selection handle tap detection

content/browser/renderer_host/input/touch_handle.cc

 // 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 "content/browser/renderer_host/input/touch_handle.h"
 
 #include <cmath>
 
 namespace content {
 
@@ skipping 22 matching lines @@
 TouchHandle::TouchHandle(TouchHandleClient* client,
                          TouchHandleOrientation orientation)
     : drawable_(client->CreateDrawable()),
       client_(client),
       orientation_(orientation),
       deferred_orientation_(TOUCH_HANDLE_ORIENTATION_UNDEFINED),
       alpha_(0.f),
       animate_deferred_fade_(false),
       enabled_(true),
       is_visible_(false),
-      is_dragging_(false) {
+      is_dragging_(false),
+      is_drag_within_tap_region_(false) {
   DCHECK_NE(orientation, TOUCH_HANDLE_ORIENTATION_UNDEFINED);
   drawable_->SetEnabled(enabled_);
   drawable_->SetOrientation(orientation_);
   drawable_->SetAlpha(alpha_);
   drawable_->SetVisible(is_visible_);
   drawable_->SetFocus(position_);
 }
 
 TouchHandle::~TouchHandle() {
 }
@@ skipping 79 matching lines @@
                                   touch_size);
       if (!drawable_->IntersectsWith(touch_rect))
         return false;
       touch_down_position_ = gfx::PointF(event.GetX(), event.GetY());
       touch_to_focus_offset_ = position_ - touch_down_position_;
       touch_down_time_ = event.GetEventTime();
       BeginDrag();
     } break;
 
     case ui::MotionEvent::ACTION_MOVE: {
-      gfx::PointF new_position =
-          gfx::PointF(event.GetX(), event.GetY()) + touch_to_focus_offset_;
-      client_->OnHandleDragUpdate(*this, new_position);
+      gfx::PointF touch_move_position(event.GetX(), event.GetY());
+      if (is_drag_within_tap_region_) {

[raghu, 2014/08/28 03:00:33]

Please correct me here if I am wrong. Do we need this condition. I think
|is_drag_within_tap_region_| will always be true here.

[jdduke (slow), 2014/08/28 15:37:12]

It will only be true until we exceed the slop region, after which it will be
false and we can shortcut the calculation.

+        const float tap_slop = client_->GetTapSlop();
+        is_drag_within_tap_region_ =
+            (touch_move_position - touch_down_position_).LengthSquared() <
+            tap_slop * tap_slop;
+      }
+
+      // Note that we signal drag update even if we're inside the tap region,
+      // as there are cases where characters are narrower than the slop length.
+      client_->OnHandleDragUpdate(*this,
+                                  touch_move_position + touch_to_focus_offset_);
     } break;
 
     case ui::MotionEvent::ACTION_UP: {
-      // TODO(jdduke): Use the platform touch slop distance and tap delay to
-      // properly detect a tap, crbug.com/394093.
-      base::TimeDelta delay = event.GetEventTime() - touch_down_time_;
-      if (delay < base::TimeDelta::FromMilliseconds(180))
+      if (is_drag_within_tap_region_ &&
+          (event.GetEventTime() - touch_down_time_) <
+              client_->GetTapTimeout()) {
         client_->OnHandleTapped(*this);
+      }
 
       EndDrag();
     } break;
 
     case ui::MotionEvent::ACTION_CANCEL:
       EndDrag();
       break;
 
     default:
       break;
@@ skipping 21 matching lines @@
 
   return true;
 }
 
 void TouchHandle::BeginDrag() {
   DCHECK(enabled_);
   if (is_dragging_)
     return;
   EndFade();
   is_dragging_ = true;
+  is_drag_within_tap_region_ = true;
   client_->OnHandleDragBegin(*this);
 }
 
 void TouchHandle::EndDrag() {
   DCHECK(enabled_);
   if (!is_dragging_)
     return;
 
   is_dragging_ = false;
+  is_drag_within_tap_region_ = false;
   client_->OnHandleDragEnd(*this);
 
   if (deferred_orientation_ != TOUCH_HANDLE_ORIENTATION_UNDEFINED) {
     TouchHandleOrientation deferred_orientation = deferred_orientation_;
     deferred_orientation_ = TOUCH_HANDLE_ORIENTATION_UNDEFINED;
     SetOrientation(deferred_orientation);
   }
 
   if (animate_deferred_fade_) {
     BeginFade();
@@ skipping 32 matching lines @@
 
 void TouchHandle::SetAlpha(float alpha) {
   alpha = std::max(0.f, std::min(1.f, alpha));
   if (alpha_ == alpha)
     return;
   alpha_ = alpha;
   drawable_->SetAlpha(alpha);
 }
 
 }  // namespace content