Relanding this as this caused layout tests failures on Win7 due to the call to ShowScrollBars being…

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 389 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) {
+      needs_scroll_styles_(false),
+      in_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)) {
+      AddScrollStylesToWindow(hwnd());
+      needs_scroll_styles_ = true;
+    }
+  }
+#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 920 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() {
+  in_size_move_loop_ = true;
+
+  // Please refer to the comments in the OnSize function about the scrollbar
+  // hack.
+  // Hide the Windows scrollbar if the scroll styles are present to ensure
+  // that a paint flicker does not occur while sizing.
+  if (needs_scroll_styles_)
+    ShowScrollBar(hwnd(), SB_BOTH, FALSE);
+
   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);
+  in_size_move_loop_ = false;
+  // Please refer to the notes in the OnSize function for information about
+  // the scrolling hack.
+  // We hide the Windows scrollbar in the OnEnterSizeMove function. We need
+  // to add the scroll styles back to ensure that scrolling works in legacy
+  // trackpoint drivers.
+  if (needs_scroll_styles_)
+    AddScrollStylesToWindow(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 @@
 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 (scroll_styles_set_) {
+  // We want the scroll styles 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 to ensure that we
+  // don't get nested WM_SIZE messages.
+  if (needs_scroll_styles_ && !in_size_move_loop_) {
     ShowScrollBar(hwnd(), SB_BOTH, FALSE);
     base::MessageLoop::current()->PostTask(
-        FROM_HERE,
-        base::Bind(&AddScrollStylesToWindow, hwnd()));
+        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