Fix the 17px dead region in the bottom right corner of top level browser windows.

ui/views/win/hwnd_message_handler.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 "ui/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 #include <wtsapi32.h>
 #pragma comment(lib, "wtsapi32.lib")
@@ skipping 1887 matching lines @@
   MapWindowPoints(HWND_DESKTOP, hwnd(), &temp, 1);
   int component = delegate_->GetNonClientComponent(gfx::Point(temp));
   if (component != HTNOWHERE)
     return component;
 
   // Otherwise, we let Windows do all the native frame non-client handling for
   // us.
 #if defined(USE_AURA)
   LRESULT hit_test_code = DefWindowProc(hwnd(), WM_NCHITTEST, 0,
                                         MAKELPARAM(point.x, point.y));
-  // If we faked the WS_VSCROLL and WS_HSCROLL styles for this window, then
-  // Windows returns the HTVSCROLL or HTHSCROLL hit test codes if we hover or
-  // click on the non client portions of the window where the OS scrollbars
-  // would be drawn. These hittest codes are returned even when the scrollbars
-  // are hidden, which is the case in Aura. We fake the hittest code as
-  // HTCLIENT in this case to ensure that we receive client mouse messages as
-  // opposed to non client mouse messages.
-  if (needs_scroll_styles_ && (hit_test_code == HTVSCROLL ||
-      hit_test_code == HTHSCROLL))
-    hit_test_code = HTCLIENT;
+  if (needs_scroll_styles_) {
+    switch (hit_test_code) {
+      // If we faked the WS_VSCROLL and WS_HSCROLL styles for this window, then
+      // Windows returns the HTVSCROLL or HTHSCROLL hit test codes if we hover
+      // or click on the non client portions of the window where the OS
+      // scrollbars would be drawn. These hittest codes are returned even when
+      // the scrollbars are hidden, which is the case in Aura. We fake the
+      // hittest code as HTCLIENT in this case to ensure that we receive client
+      // mouse messages as opposed to non client mouse messages.
+      case HTVSCROLL:
+      case HTHSCROLL:
+        hit_test_code = HTCLIENT;
+        break;
+
+      case HTBOTTOMRIGHT: {
+        // Normally the HTBOTTOMRIGHT hittest code is received when we hover
+        // near the bottom right of the window. However due to our fake scroll
+        // styles, we get this code even when we hover around the area where
+        // the vertical scrollar down arrow would be drawn.
+        // We check if the hittest coordinates lie in this region and if yes
+        // we return HTCLIENT.
+        int border_width = ::GetSystemMetrics(SM_CXSIZEFRAME);
+        int border_height = ::GetSystemMetrics(SM_CYSIZEFRAME);
+        int scroll_width = ::GetSystemMetrics(SM_CXVSCROLL);
+        int scroll_height = ::GetSystemMetrics(SM_CYVSCROLL);
+        RECT window_rect;
+        ::GetWindowRect(hwnd(), &window_rect);
+        window_rect.bottom -= border_height;
+        window_rect.right -= border_width;
+        window_rect.left = window_rect.right - scroll_width;
+        window_rect.top = window_rect.bottom - scroll_height;
+        POINT pt;
+        pt.x = point.x;
+        pt.y = point.y;
+        if (::PtInRect(&window_rect, pt))
+          hit_test_code = HTCLIENT;
+        break;
+      }
+
+      default:
+        break;
+    }
+  }
   return hit_test_code;
 #else
   SetMsgHandled(FALSE);
 #endif
 }
 
 void HWNDMessageHandler::OnNCPaint(HRGN rgn) {
   // We only do non-client painting if we're not using the native frame.
   // It's required to avoid some native painting artifacts from appearing when
   // the window is resized.
@@ skipping 460 matching lines @@
   SetMsgHandled(FALSE);
 }
 
 void HWNDMessageHandler::HandleTouchEvents(const TouchEvents& touch_events) {
   base::WeakPtr<HWNDMessageHandler> ref(weak_factory_.GetWeakPtr());
   for (size_t i = 0; i < touch_events.size() && ref; ++i)
     delegate_->HandleTouchEvent(touch_events[i]);
 }
 
 }  // namespace views