1 files changed, 116 insertions, 0 deletions
diff --git a/chrome/views/focus/focus_util_win.cc b/chrome/views/focus/focus_util_win.cc
new file mode 100644
index 0000000..ec77519
--- /dev/null
+++ b/chrome/views/focus/focus_util_win.cc
@@ -0,0 +1,116 @@
+// Copyright (c) 2009 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/views/focus/focus_util_win.h"
+
+#include "base/win_util.h"
+
+namespace views {
+
+// Property used to indicate the HWND supports having mouse wheel messages
+// rerouted to it.
+static const wchar_t* const kHWNDSupportMouseWheelRerouting =
+    L"__HWND_MW_REROUTE_OK";
+
+static bool WindowSupportsRerouteMouseWheel(HWND window) {
+  while (GetWindowLong(window, GWL_STYLE) & WS_CHILD) {
+    if (!IsWindow(window))
+      break;
+
+    if (reinterpret_cast<bool>(GetProp(window,
+                                       kHWNDSupportMouseWheelRerouting))) {
+      return true;
+    }
+    window = GetParent(window);
+  }
+  return false;
+}
+
+static bool IsCompatibleWithMouseWheelRedirection(HWND window) {
+  std::wstring class_name = win_util::GetClassName(window);
+  // Mousewheel redirection to comboboxes is a surprising and
+  // undesireable user behavior.
+  return !(class_name == L"ComboBox" ||
+           class_name == L"ComboBoxEx32");
+}
+
+static bool CanRedirectMouseWheelFrom(HWND window) {
+  std::wstring class_name = win_util::GetClassName(window);
+
+  // Older Thinkpad mouse wheel drivers create a window under mouse wheel
+  // pointer. Detect if we are dealing with this window. In this case we
+  // don't need to do anything as the Thinkpad mouse driver will send
+  // mouse wheel messages to the right window.
+  if ((class_name == L"Syn Visual Class") ||
+     (class_name == L"SynTrackCursorWindowClass"))
+    return false;
+
+  return true;
+}
+
+void SetWindowSupportsRerouteMouseWheel(HWND hwnd) {
+  SetProp(hwnd, kHWNDSupportMouseWheelRerouting,
+          reinterpret_cast<HANDLE>(true));
+}
+
+bool RerouteMouseWheel(HWND window, WPARAM w_param, LPARAM l_param) {
+  // Since this is called from a subclass for every window, we can get
+  // here recursively. This will happen if, for example, a control
+  // reflects wheel scroll messages to its parent. Bail out if we got
+  // here recursively.
+  static bool recursion_break = false;
+  if (recursion_break)
+    return false;
+  // Check if this window's class has a bad interaction with rerouting.
+  if (!IsCompatibleWithMouseWheelRedirection(window))
+    return false;
+
+  DWORD current_process = GetCurrentProcessId();
+  POINT wheel_location = { GET_X_LPARAM(l_param), GET_Y_LPARAM(l_param) };
+  HWND window_under_wheel = WindowFromPoint(wheel_location);
+
+  if (!CanRedirectMouseWheelFrom(window_under_wheel))
+    return false;
+
+  // Find the lowest Chrome window in the hierarchy that can be the
+  // target of mouse wheel redirection.
+  while (window != window_under_wheel) {
+    // If window_under_wheel is not a valid Chrome window, then return true to
+    // suppress further processing of the message.
+    if (!::IsWindow(window_under_wheel))
+      return true;
+    DWORD wheel_window_process = 0;
+    GetWindowThreadProcessId(window_under_wheel, &wheel_window_process);
+    if (current_process != wheel_window_process) {
+      if (IsChild(window, window_under_wheel)) {
+        // If this message is reflected from a child window in a different
+        // process (happens with out of process windowed plugins) then
+        // we don't want to reroute the wheel message.
+        return false;
+      } else {
+        // The wheel is scrolling over an unrelated window. Make sure that we
+        // have marked that window as supporting mouse wheel rerouting.
+        // Otherwise, we cannot send random WM_MOUSEWHEEL messages to arbitrary
+        // windows. So just drop the message.
+        if (!WindowSupportsRerouteMouseWheel(window_under_wheel))
+          return true;
+      }
+    }
+
+    // window_under_wheel is a Chrome window.  If allowed, redirect.
+    if (IsCompatibleWithMouseWheelRedirection(window_under_wheel)) {
+      recursion_break = true;
+      SendMessage(window_under_wheel, WM_MOUSEWHEEL, w_param, l_param);
+      recursion_break = false;
+      return true;
+    }
+    // If redirection is disallowed, try the parent.
+    window_under_wheel = GetAncestor(window_under_wheel, GA_PARENT);
+  }
+  // If we traversed back to the starting point, we should process
+  // this message normally; return false.
+  return false;
+}
+
+}  // namespace views