Re-land r51526

views/controls/scrollbar/native_scroll_bar_win.cc

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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 "views/controls/scrollbar/native_scroll_bar_win.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/keyboard_codes.h"
 #include "base/message_loop.h"
@@ skipping 181 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(ScrollBarContainer);
 };
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeScrollBarWin, public:
 
 NativeScrollBarWin::NativeScrollBarWin(NativeScrollBar* scroll_bar)
     : native_scroll_bar_(scroll_bar),
       sb_container_(NULL) {
   set_focus_view(scroll_bar);
+  memset(&scroll_info_, 0, sizeof(scroll_info_));
 }
 
 NativeScrollBarWin::~NativeScrollBarWin() {
-  if (sb_container_) {
+  if (sb_container_.get()) {
     // We always destroy the scrollbar container explicitly to cover all
     // cases including when the container is no longer connected to a
     // widget tree.
     DestroyWindow(sb_container_->hwnd());
-    delete sb_container_;
   }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeScrollBarWin, View overrides:
 
 void NativeScrollBarWin::Layout() {
   SetBounds(native_scroll_bar_->GetLocalBounds(true));
   NativeControlWin::Layout();
 }
 
 gfx::Size NativeScrollBarWin::GetPreferredSize() {
   if (native_scroll_bar_->IsHorizontal())
     return gfx::Size(0, GetHorizontalScrollBarHeight());
   return gfx::Size(GetVerticalScrollBarWidth(), 0);
 }
 
 bool NativeScrollBarWin::OnKeyPressed(const KeyEvent& event) {
-  if (!sb_container_)
+  if (!sb_container_.get())
     return false;
   int code = -1;
   switch (event.GetKeyCode()) {
     case base::VKEY_UP:
       if (!native_scroll_bar_->IsHorizontal())
         code = SB_LINEUP;
       break;
     case base::VKEY_PRIOR:
       code = SB_PAGEUP;
       break;
@@ skipping 22 matching lines @@
   if (code != -1) {
     SendMessage(sb_container_->hwnd(),
                 native_scroll_bar_->IsHorizontal() ? WM_HSCROLL : WM_VSCROLL,
                 MAKELONG(static_cast<WORD>(code), 0), 0L);
     return true;
   }
   return false;
 }
 
 bool NativeScrollBarWin::OnMouseWheel(const MouseWheelEvent& e) {
-  if (!sb_container_)
+  if (!sb_container_.get())
     return false;
   sb_container_->ScrollWithOffset(e.GetOffset());
   return true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeScrollBarWin, NativeControlWin overrides:
 
 void NativeScrollBarWin::CreateNativeControl() {
-  sb_container_ = new ScrollBarContainer(native_scroll_bar_);
+  sb_container_.reset(new ScrollBarContainer(native_scroll_bar_));
   NativeControlCreated(sb_container_->hwnd());
+  // Reinstall scroll state if we have valid information.
+  if (scroll_info_.cbSize)
+    SetScrollInfo(sb_container_->GetScrollBarHWND(), SB_CTL, &scroll_info_,
+                  TRUE);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeScrollBarWin, NativeScrollBarWrapper overrides:
 
 int NativeScrollBarWin::GetPosition() const {
   SCROLLINFO si;
   si.cbSize = sizeof(si);
   si.fMask = SIF_POS;
   GetScrollInfo(sb_container_->GetScrollBarHWND(), SB_CTL, &si);
   return si.nPos;
 }
 
 View* NativeScrollBarWin::GetView() {
   return this;
 }
 
 void NativeScrollBarWin::Update(int viewport_size,
                                 int content_size,
                                 int current_pos) {
-  if (!sb_container_)
+  if (!sb_container_.get())
     return;
 
   if (content_size < 0)
     content_size = 0;
 
   if (current_pos < 0)
     current_pos = 0;
 
   if (current_pos > content_size)
     current_pos = content_size;
 
-  SCROLLINFO si;
-  si.cbSize = sizeof(si);
-  si.fMask = SIF_DISABLENOSCROLL | SIF_POS | SIF_RANGE | SIF_PAGE;
-  si.nMin = 0;
-  si.nMax = content_size;
-  si.nPos = current_pos;
-  si.nPage = viewport_size;
-  SetScrollInfo(sb_container_->GetScrollBarHWND(), SB_CTL, &si, TRUE);
+  scroll_info_.cbSize = sizeof(scroll_info_);
+  scroll_info_.fMask = SIF_DISABLENOSCROLL | SIF_POS | SIF_RANGE | SIF_PAGE;
+  scroll_info_.nMin = 0;
+  scroll_info_.nMax = content_size;
+  scroll_info_.nPos = current_pos;
+  scroll_info_.nPage = viewport_size;
+  SetScrollInfo(sb_container_->GetScrollBarHWND(), SB_CTL, &scroll_info_, TRUE);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativewScrollBarWrapper, public:
 
 // static
 NativeScrollBarWrapper* NativeScrollBarWrapper::CreateWrapper(
     NativeScrollBar* scroll_bar) {
   return new NativeScrollBarWin(scroll_bar);
 }
 
 // static
 int NativeScrollBarWrapper::GetHorizontalScrollBarHeight() {
   return GetSystemMetrics(SM_CYHSCROLL);
 }
 
 // static
 int NativeScrollBarWrapper::GetVerticalScrollBarWidth() {
   return GetSystemMetrics(SM_CXVSCROLL);
 }
 
 }  // namespace views
-