Ensure that trackpad and trackpoint scrolling works on Windows desktop Aura with legacy trackpad dr…

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 "base/bind.h"
@@ skipping 281 matching lines @@
   }
 
   return false;
 }
 
 #endif
 
 // The thickness of an auto-hide taskbar in pixels.
 const int kAutoHideTaskbarThicknessPx = 2;
 
+bool IsTopLevelWindow(HWND window) {

[sky, 2014/01/10 19:18:42]

Is this still needed? Can't you key off the styles at the time you create the
window and set some boolean?

[ananta, 2014/01/10 20:05:36]

Removed. Added a member flag

+  long style = GetWindowLong(window, GWL_STYLE);
+  if (!(style & WS_CHILD))
+    return true;
+
+  HWND parent = GetParent(window);
+  return !parent || (parent == GetDesktopWindow());
+}
+
+void AddScrollStylesToWindow(HWND window) {
+  if (::IsWindow(window)) {
+    DCHECK(IsTopLevelWindow(window));
+    long current_style = ::GetWindowLong(window, GWL_STYLE);
+    ::SetWindowLong(window, GWL_STYLE,
+                    current_style | WS_VSCROLL | WS_HSCROLL);
+  }
+}
+
 }  // namespace
 
 // A scoping class that prevents a window from being able to redraw in response
 // to invalidations that may occur within it for the lifetime of the object.
 //
 // Why would we want such a thing? Well, it turns out Windows has some
 // "unorthodox" behavior when it comes to painting its non-client areas.
 // Occasionally, Windows will paint portions of the default non-client area
 // right over the top of the custom frame. This is not simply fixed by handling
 // WM_NCPAINT/WM_PAINT, with some investigation it turns out that this
@@ skipping 1646 matching lines @@
   EndPaint(hwnd(), &ps);
 }
 
 LRESULT HWNDMessageHandler::OnReflectedMessage(UINT message,
                                                WPARAM w_param,
                                                LPARAM l_param) {
   SetMsgHandled(FALSE);
   return 0;
 }
 
+LRESULT HWNDMessageHandler::OnScrollMessage(UINT message,
+                                            WPARAM w_param,
+                                            LPARAM l_param) {
+  MSG msg = { hwnd(), message, w_param, l_param, GetMessageTime() };
+  ui::ScrollEvent event(msg);
+  delegate_->HandleScrollEvent(event);
+  return 0;
+}
+
 LRESULT HWNDMessageHandler::OnSetCursor(UINT message,
                                         WPARAM w_param,
                                         LPARAM l_param) {
   // Reimplement the necessary default behavior here. Calling DefWindowProc can
   // trigger weird non-client painting for non-glass windows with custom frames.
   // Using a ScopedRedrawLock to prevent caption rendering artifacts may allow
   // content behind this window to incorrectly paint in front of this window.
   // Invalidating the window to paint over either set of artifacts is not ideal.
   wchar_t* cursor = IDC_ARROW;
   switch (LOWORD(l_param)) {
@@ skipping 57 matching lines @@
       delegate_->HandleWorkAreaChanged();
     SetMsgHandled(FALSE);
   }
 }
 
 void HWNDMessageHandler::OnSize(UINT param, const CSize& size) {
   RedrawWindow(hwnd(), NULL, NULL, RDW_INVALIDATE | RDW_ALLCHILDREN);
   // ResetWindowRegion is going to trigger WM_NCPAINT. By doing it after we've
   // invoked OnSize we ensure the RootView has been laid out.
   ResetWindowRegion(false, true);
+
+#if defined(USE_AURA)
+  // We add the WS_VSCROLL and WS_HSCROLL styles to top level windows to ensure
+  // that legacy trackpad/trackpoint drivers generate the WM_VSCROLL and
+  // WM_HSCROLL messages and scrolling works.
+  // We want the style to be present on the window. However we don't want
+  // Windows to draw the scrollbars. To achieve this we hide the scroll bars
+  // and readd them to the window style in a posted task which works.
+  if (IsTopLevelWindow(hwnd())) {
+    BOOL visible = ::IsWindowVisible(hwnd());
+    ShowScrollBar(hwnd(), SB_BOTH, FALSE);
+    long current_style = ::GetWindowLong(hwnd(), GWL_STYLE);
+    base::MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&AddScrollStylesToWindow, hwnd()));
+#endif
+  }
 }
 
 void HWNDMessageHandler::OnSysCommand(UINT notification_code,
                                       const CPoint& point) {
   if (!delegate_->ShouldHandleSystemCommands())
     return;
 
   // Windows uses the 4 lower order bits of |notification_code| for type-
   // specific information so we must exclude this when comparing.
   static const int sc_mask = 0xFFF0;
@@ skipping 200 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