Don't set the scroll styles (WS_VSCROLL and WS_HSCROLL) for WS_POPUP 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 "base/bind.h"
@@ skipping 297 matching lines @@
 }
 
 void AddScrollStylesToWindow(HWND window) {
   if (::IsWindow(window)) {
     long current_style = ::GetWindowLong(window, GWL_STYLE);
     ::SetWindowLong(window, GWL_STYLE,
                     current_style | WS_VSCROLL | WS_HSCROLL);
   }
 }
 
+void HideWindowsScrollBar(HWND window) {
+  ShowScrollBar(window, SB_BOTH, FALSE);
+  base::MessageLoop::current()->PostTask(

[sky, 2014/01/15 15:41:32]

Document why the post task.

[ananta, 2014/01/15 16:54:58]

Done.

+      FROM_HERE,
+      base::Bind(&AddScrollStylesToWindow, window));
+}
+
 }  // 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 72 matching lines @@
       lock_updates_count_(0),
       ignore_window_pos_changes_(false),
       last_monitor_(NULL),
       use_layered_buffer_(false),
       layered_alpha_(255),
       waiting_for_redraw_layered_window_contents_(false),
       is_first_nccalc_(true),
       menu_depth_(0),
       autohide_factory_(this),
       id_generator_(0),
-      scroll_styles_set_(false) {
+      scroll_styles_set_(false),
+      size_move_loop_(false) {
 }
 
 HWNDMessageHandler::~HWNDMessageHandler() {
   delegate_ = NULL;
   // Prevent calls back into this class via WNDPROC now that we've been
   // destroyed.
   ClearUserData();
 }
 
 void HWNDMessageHandler::Init(HWND parent, const gfx::Rect& bounds) {
   TRACE_EVENT0("views", "HWNDMessageHandler::Init");
   GetMonitorAndRects(bounds.ToRECT(), &last_monitor_, &last_monitor_rect_,
                      &last_work_area_);
 
   // Create the window.
   WindowImpl::Init(parent, bounds);
+
+#if defined(USE_AURA)
+  // 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 add these styles to ensure that trackpad/trackpoint scrolling
+  // work.
+  // TODO(ananta)
+  // Look into moving the WS_VSCROLL and WS_HSCROLL style setting logic to the
+  // CalculateWindowStylesFromInitParams function. Doing it there seems to
+  // cause some interactive tests to fail. Investigation needed.
+  if (IsTopLevelWindow(hwnd())) {
+    long current_style = ::GetWindowLong(hwnd(), GWL_STYLE);
+    if (!(current_style & WS_POPUP)) {
+      ::SetWindowLong(hwnd(), GWL_STYLE,

[sky, 2014/01/15 15:41:32]

Can you use AddScrollStylesToWindow?

[ananta, 2014/01/15 16:54:58]

Done.

+                      current_style | WS_VSCROLL | WS_HSCROLL);
+      scroll_styles_set_ = true;

[sky, 2014/01/15 15:41:32]

How about naming this needs_scroll_styles_?

[ananta, 2014/01/15 16:54:58]

Done.

+    }
+  }
+#endif
 }
 
 void HWNDMessageHandler::InitModalType(ui::ModalType modal_type) {
   if (modal_type == ui::MODAL_TYPE_NONE)
     return;
   // We implement modality by crawling up the hierarchy of windows starting
   // at the owner, disabling all of them so that they don't receive input
   // messages.
   HWND start = ::GetWindow(hwnd(), GW_OWNER);
   while (start) {
@@ skipping 922 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)
-  // 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 add these styles to ensure that trackpad/trackpoint scrolling
-  // work.
-  // TODO(ananta)
-  // Look into moving the WS_VSCROLL and WS_HSCROLL style setting logic to the
-  // CalculateWindowStylesFromInitParams function. Doing it there seems to
-  // cause some interactive tests to fail. Investigation needed.
-  if (IsTopLevelWindow(hwnd())) {
-    long current_style = ::GetWindowLong(hwnd(), GWL_STYLE);
-    ::SetWindowLong(hwnd(), GWL_STYLE,
-                    current_style | WS_VSCROLL | WS_HSCROLL);
-    scroll_styles_set_ = true;
-  }
-#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 11 matching lines @@
   FrameTypeChanged();
   return 0;
 }
 
 void HWNDMessageHandler::OnEnterMenuLoop(BOOL from_track_popup_menu) {
   if (menu_depth_++ == 0)
     delegate_->HandleMenuLoop(true);
 }
 
 void HWNDMessageHandler::OnEnterSizeMove() {
+  size_move_loop_ = true;
   delegate_->HandleBeginWMSizeMove();
   SetMsgHandled(FALSE);
 }
 
 LRESULT HWNDMessageHandler::OnEraseBkgnd(HDC dc) {
   // Needed to prevent resize flicker.
   return 1;
 }
 
 void HWNDMessageHandler::OnExitMenuLoop(BOOL is_shortcut_menu) {
   if (--menu_depth_ == 0)
     delegate_->HandleMenuLoop(false);
   DCHECK_GE(0, menu_depth_);
 }
 
 void HWNDMessageHandler::OnExitSizeMove() {
   delegate_->HandleEndWMSizeMove();
   SetMsgHandled(FALSE);
+  size_move_loop_ = false;
+  // Please refer to the notes in the OnSize function for information about
+  // the scrolling hack.
+  if (scroll_styles_set_)
+    HideWindowsScrollBar(hwnd());
 }
 
 void HWNDMessageHandler::OnGetMinMaxInfo(MINMAXINFO* minmax_info) {
   gfx::Size min_window_size;
   gfx::Size max_window_size;
   delegate_->GetMinMaxSize(&min_window_size, &max_window_size);
 
   // Add the native frame border size to the minimum and maximum size if the
   // view reports its size as the client size.
   if (delegate_->WidgetSizeIsClientSize()) {
@@ skipping 647 matching lines @@
   // 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 (scroll_styles_set_) {
-    ShowScrollBar(hwnd(), SB_BOTH, FALSE);
-    base::MessageLoop::current()->PostTask(
-        FROM_HERE,
-        base::Bind(&AddScrollStylesToWindow, hwnd()));
+  // If we are in the context of a size loop operation, we do this when the
+  // sizing operation completes.
+  if (scroll_styles_set_ && !size_move_loop_)
+    HideWindowsScrollBar(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