Tab close buttons can only be targeted with touch if the whole button is visible

chrome/browser/ui/views/tabs/tab.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/views/tabs/tab.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/debug/alias.h"
@@ skipping 401 matching lines @@
     // button is hidden behind another tab.
     gfx::Path tab_mask;
     tab_->GetHitTestMask(source, &tab_mask);
 
     gfx::Rect button_bounds(GetContentsBounds());
     button_bounds.set_x(GetMirroredXForRect(button_bounds));
     gfx::RectF tab_bounds_f(gfx::SkRectToRectF(tab_mask.getBounds()));
     views::View::ConvertRectToTarget(tab_, this, &tab_bounds_f);
     gfx::Rect tab_bounds = gfx::ToEnclosingRect(tab_bounds_f);
 
-    // If the button is hidden behind another tab, the hit test mask is empty.
-    // Otherwise set the hit test mask to be the contents bounds.
+    // If either the top or bottom of the tab close button is clipped,
+    // do not consider these regions to be part of the button's bounds.
+    int top_overflow = tab_bounds.y() - button_bounds.y();
+    int bottom_overflow = button_bounds.bottom() - tab_bounds.bottom();
+    if (top_overflow > 0)
+      button_bounds.set_y(tab_bounds.y());
+    else if (bottom_overflow > 0)
+      button_bounds.set_height(button_bounds.height() - bottom_overflow);
+
+    // If the hit test request is in response to a gesture, |path| should be
+    // empty unless the entire tab close button is visible to the user. Hit
+    // test requests in response to a mouse event should always set |path|
+    // to be the visible portion of the tab close button, even if it is
+    // partially hidden behind another tab.
     path->reset();
-    if (tab_bounds.Intersects(button_bounds)) {
-      // Include the padding in the hit test mask for touch events.
-      if (source == HIT_TEST_SOURCE_TOUCH)
-        button_bounds = GetLocalBounds();
+    gfx::Rect intersection(gfx::IntersectRects(tab_bounds, button_bounds));
+    if (!intersection.IsEmpty()) {
+      // TODO(tdanderson): Consider always returning the intersection if
+      // the non-rectangular shape of the tabs can be accounted for.
+      if (source == HIT_TEST_SOURCE_TOUCH &&
+          !tab_bounds.Contains(button_bounds))
+        return;
 
-      // TODO: this isn't quite right, really need to intersect the two regions.
-      path->addRect(RectToSkRect(button_bounds));
+      path->addRect(RectToSkRect(intersection));
     }
   }
 
   virtual const char* GetClassName() const OVERRIDE {
     return kTabCloseButtonName;
   }
 
  private:
   Tab* tab_;
 
@@ skipping 1297 matching lines @@
                          const gfx::ImageSkia& image) {
   DCHECK_NE(scale_factor, ui::SCALE_FACTOR_NONE);
   ImageCacheEntry entry;
   entry.resource_id = resource_id;
   entry.scale_factor = scale_factor;
   entry.image = image;
   image_cache_->push_front(entry);
   if (image_cache_->size() > kMaxImageCacheSize)
     image_cache_->pop_back();
 }