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) {
+  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 1024 matching lines @@
 #if !defined(USE_AURA)
   // We need to add ourselves as a message loop observer so that we can repaint
   // aggressively if the contents of our window become invalid. Unfortunately
   // WM_PAINT messages are starved and we get flickery redrawing when resizing
   // if we do not do this.
   base::MessageLoopForUI::current()->AddObserver(this);
 #endif
 
   delegate_->HandleCreate();
 
+#if defined(USE_AURA)

[sky, 2014/01/10 16:43:21]

Can this be moved to CalculateWindowStylesFromInitParams and passed in so that
we don't have to check each time if we should add/remove the style?

[ananta, 2014/01/10 18:59:21]

Done.

+  // Certain trackpad drivers on Windows have bugs where in they don't generate
+  // WM_MOUSEWHEEL messages for the trackpoint and trackpad scrolling gestures
+  // unless there is an entry for Chrome with the class name of the Window.
+  // These drivers check if the window under the trackpoint has the WS_VSCROLL/
+  // WS_HSCROLL style and if yes they generate the legacy WM_VSCROLL/WM_HSCROLL
+  // messages. 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())) {
+    long current_style = ::GetWindowLong(hwnd(), GWL_STYLE);
+    ::SetWindowLong(hwnd(), GWL_STYLE,
+                    current_style | WS_VSCROLL | WS_HSCROLL);
+  }
+#endif
   // TODO(beng): move more of NWW::OnCreate here.
   return 0;
 }
 
 void HWNDMessageHandler::OnDestroy() {
   delegate_->HandleDestroying();
 }
 
 void HWNDMessageHandler::OnDisplayChange(UINT bits_per_pixel,
                                          const CSize& screen_size) {
@@ skipping 679 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)
+  // As documented in the HWNDMessageHandler::OnCreate function, we add the
+  // WS_VSCROLL and WS_HSCROLL styles to the window to ensure that legacy track
+  // pad/trackpoint drivers generate the WM_VSCROLL and WM_HSCROLL messages.
+  // 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

[sky, 2014/01/10 16:43:21]

Could we instead set the scrollbar sizes to 0?

[ananta, 2014/01/10 18:59:21]

Tricky to do that. The non AURA code did this in the WebContentsViewWin class
which parented the RenderWidgetHostViewWin window. It returned 0 in its
nccalcsize handler to set the scrollbar size to 0. Tricky to do that in AURA
given that we have one window and this would require mucking with the nccalcsize
rects.

+  // 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 193 matching lines @@
     MARGINS m = {10, 10, 10, 10};
     DwmExtendFrameIntoClientArea(hwnd(), &m);
   }
   if (window_pos->flags & SWP_SHOWWINDOW)
     delegate_->HandleVisibilityChanged(true);
   else if (window_pos->flags & SWP_HIDEWINDOW)
     delegate_->HandleVisibilityChanged(false);
   SetMsgHandled(FALSE);
 }
 
+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;
+}
+
 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