Use a minimum touch size for selection handle hit testing

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 {
 
 namespace {
 
 // Maximum duration of a fade sequence.
 const double kFadeDurationMs = 200;
 
 // Maximum amount of travel for a fade sequence. This avoids handle "ghosting"
 // when the handle is moving rapidly while the fade is active.
 const double kFadeDistanceSquared = 20.f * 20.f;
 
+// Avoid using an empty touch rect, as it may fail the intersection test event
+// if it lies within the other rect's bounds.
+const float kMinTouchMajorForHitTesting = 1.f;
+
 // The maximum touch size to use when computing whether a touch point is
 // targetting a touch handle. This is necessary for devices that misreport
 // touch radii, preventing inappropriately largely touch sizes from completely
 // breaking handle dragging behavior.
-const float kMaxTouchMajorForHitTesting = 48.f;
+const float kMaxTouchMajorForHitTesting = 36.f;
 
 }  // namespace
 
 // Responsible for rendering a selection or insertion handle for text editing.
 TouchHandle::TouchHandle(TouchHandleClient* client,
                          TouchHandleOrientation orientation)
     : drawable_(client->CreateDrawable()),
       client_(client),
       orientation_(orientation),
       deferred_orientation_(TOUCH_HANDLE_ORIENTATION_UNDEFINED),
@@ skipping 78 matching lines @@
   if (!enabled_)
     return false;
 
   if (!is_dragging_ && event.GetAction() != ui::MotionEvent::ACTION_DOWN)
     return false;
 
   switch (event.GetAction()) {
     case ui::MotionEvent::ACTION_DOWN: {
       if (!is_visible_)
         return false;
-      const float touch_size =
-          std::min(event.GetTouchMajor(), kMaxTouchMajorForHitTesting);
+      const float touch_size = std::max(
+          kMinTouchMajorForHitTesting,
+          std::min(kMaxTouchMajorForHitTesting, event.GetTouchMajor()));
       const gfx::RectF touch_rect(event.GetX() - touch_size * .5f,
                                   event.GetY() - touch_size * .5f,
                                   touch_size,
                                   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();
@@ skipping 106 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