自绘LISTVIEW的滚动条(Delphi实现)

因项目需要准备对LISTVIEW的滚动条进行自绘。于是在网上搜了一下，问题没解决，却搜出一篇令人不愉快的帖子 。确实，那时候实力是不够的，但现在应该是没问题了，为这个目的才不断磨练自己的。

LISTVIEW控件的滚动条是系统自带的，它不创建窗口。对LISTVIEW窗口本身进行子类化后，要处理一些跟滚动条有关的消息。

首先是要骗过WM_NCPAINT消息。这个十分容易。WM_NCPAINT消息的wParam是一个区域的句柄。当它不为1时，从它里面CLIP 掉滚动条的区域，再传给原窗口过程即可。当它为1时，创建一个包含控件全客户区域的Region，再从中CLIP掉滚动条的区域，传给原窗口过程。

然后是WM_HSCROLL和WM_VSCROLL消息。在调用原窗口过程之前需要去掉窗口的WS_HSCROLL和WS_VSCROLL样式，否 则窗口过程就会在消息中绘制滚动条。调用后需要恢复。同时为避免窗口在WM_STYLECHANGING和WM_STYLECHANGED消息中重绘，也 需要截获这两个消息。

WM_NCCALCSIZE消息也是必须截获的。如果是在处理WM_HSCROLL和WM_VSCROLL消息的过程中响应WM_NCCALCSIZE，则必须去掉WS_HSCROLL和WS_VSCROLL样式。

然后是WM_ERASEBACKGROUND,WM_MOUSEWHELL消息。在这消息后需要重绘滚动条。

最重要的莫过于WM_NCHITTEST消息了。因为是自绘，所以滚动条的按下和拖动都必须在这里处理。

在自己写的滚动条Track函数中，最头疼的莫过于ThumbTrack了。当你计算好滚动到的绝对位置后，用SendMessage(hWnd, WM_XSCROLL, MAKEWPARAM(SB_THUMBTRACK, Pos), 0)发给窗口时，它居然没有反应。这是因为窗口过程不会从消息中取得TrackPos，而是会调用GetScrollInfo的API取得 TrackPos（因为前者只有16位）。但是使用SetScrollInfo是没办法设置TrackPos的。虽然你可以用SIF_POS标志让它同时 设置Pos和TrackPos，但当Pos等于TrackPos时，窗口过程不会做任何响应。从windows源代码中我们可以了解到，TrackPos 并不会为每个窗口保存一份，实际上，在任一时刻最多只有一个滚动条在做ThumbTrack的操作，因此系统只需要用一个全局变量来保存就可以了。

解决这个问题的办法是HookAPI。在GetScrollInfo中返回我们自己的TrackPos。要注意的是要Hook的不是本模块的 API，而是ComCtl32.dll中的GetScrollInfo。因此简单的如往@GetScrollInfo地址写几句跳转的方法是行不通的。必 须遍历ComCtl32.dll的pe头。这种技术在很多文章中都有描述。

不多说了，以下是Delphi代码，要点在前面已有描述，源码中没有做特殊说明。

使用说明：

资源中是一张横条的192*16的位图，从左到右依次是：左箭头、右箭头、上箭头、下箭头、左箭头按下、右箭头按下、上箭头按下、下箭头按下、横Thumb条、纵Thumb条、横背景条、纵背景条。

初始化时，调用GetSkinSB.InitSkinSB(ListView1.Handle);即可。窗口销毁前调用GetSkinSB.UninitSkinSB(ListView1.Handle)。

虽然也可针对EDIT(TMemo)和其它使用系统滚动条的控件使用此模块，但效果各有差异，需要分别做特殊处理。

unit  SkinSB;

interface

uses
  SysUtils, Classes, Windows, Messages, Graphics;

const
  SKINSB_PROP =  '{8BC6661E-5880-4353-878D-C3B3784CFC5F}' ;

type

  TBarPosCode = ( bpcNone,
                  bpcHArrowL, bpcHArrowR, bpcHPageL, bpcHPageR, bpcHThumb,
                  bpcVArrowU, bpcVArrowD, bpcVPageU, bpcVPageD, bpcVThumb,
                  bpcCross );

  TWindowProc =  function  (hWnd: HWND; uMsg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;

  PSkinSBInfo = ^TSkinSBInfo;
  TSkinSBInfo =  packed  record
    OldWndProc: TWindowProc;
    Prevent:  Boolean ;  // prevent style change message
    Scrolling:  Boolean ;
    Style:  Cardinal ;  // real style
    ThumbTrack:  Boolean ;
    ThumbPos:  Integer ;
    Tracking:  Boolean ;  // tracking: click arrow or track thumb
  end ;

  TSkinSB =  class
  protected
    FBitmap: TBitmap;
    constructor  CreateInstance;
  public
    constructor  Create;
    destructor  Destroy; override;
    procedure  InitSkinSB(H: HWND);
    procedure  UnInitSkinSB(H: HWND);
    procedure  DrawElem(H: HWND; Code: TBarPosCode; R: TRect; Down:  Boolean );
  end ;

function  GetSkinSB: TSkinSB;

function  SkinSBWndProc(hWnd: HWND; uMsg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
function  GetSkinSBInfo(hWnd: HWND): PSkinSBInfo;

implementation

uses
  CommCtrl;

{$R *.res}

var
  l_SkinSB: TSkinSB;
  l_SkinSB_Prop: TATOM;

type
  PImageImportDescriptor = ^TImageImportDescriptor;
  TImageImportDescriptor =  packed  record
    OriginalFirstThunk: DWORD;   // or Characteristics: DWORD
    TimeDateStamp: DWORD;
    ForwarderChain: DWORD;
    Name: DWORD;
    FirstThunk: DWORD;
  end ;
  PImageChunkData = ^TImageChunkData;
  TImageChunkData =  packed  record
    case  Integer  of
      0 : ( ForwarderString: DWORD );
      1 : ( Func: DWORD );
      2 : ( Ordinal: DWORD );
      3 : ( AddressOfData: DWORD );
  end ;
  PImageImportByName = ^TImageImportByName;
  TImageImportByName =  packed  record
    Hint:  Word ;
    Name:  array [ 0..0 ]  of  Byte ;
  end ;

type
  PHookRec = ^THookRec;
  THookRec =  packed  record
    OldFunc:  Pointer ;
    NewFunc:  Pointer ;
  end ;

var
  _HookGetScrollInfo: THookRec;

procedure  HookApiInMod(ImageBase:  Cardinal ; ApiName:  PChar ; PHook: PHookRec);
var
  pidh: PImageDosHeader;
  pinh: PImageNtHeaders;
  pSymbolTable: PIMAGEDATADIRECTORY;
  piid: PIMAGEIMPORTDESCRIPTOR;
  pitd_org, pitd_1st: PImageChunkData;
  piibn: PImageImportByName;
  pAPIFunction:  Pointer ;
  written, oldAccess: DWORD;
begin
  if  ImageBase =  0  then  Exit;
  pidh := PImageDosHeader(ImageBase);
  pinh := PImageNtHeaders(DWORD(ImageBase) +  Cardinal (pidh^._lfanew));
  pSymbolTable := @pinh^.OptionalHeader . DataDirectory[ 1 ];
  piid := PImageImportDescriptor(DWORD(ImageBase) + pSymbolTable^.VirtualAddress);
  repeat
    pitd_org := PImageChunkData(DWORD(ImageBase) + piid^.OriginalFirstThunk);
    pitd_1st := PImageChunkData(DWORD(ImageBase) + piid^.FirstThunk);
    repeat
      piibn := PImageImportByName(DWORD(ImageBase) + LPDWORD(pitd_org)^);
      pAPIFunction :=  Pointer (pitd_1st^.Func);
      if  StrComp(ApiName, @piibn^.Name) =  0  then
      begin
        PHook^.OldFunc := pAPIFunction;
        VirtualProtect(@(pitd_1st^.Func), SizeOf(DWORD), PAGE_WRITECOPY, oldAccess);
        WriteProcessMemory(GetCurrentProcess(), @(pitd_1st^.Func), @PHook^.NewFunc, SizeOf(DWORD), written);
        VirtualProtect(@(pitd_1st^.Func), SizeOf(DWORD), oldAccess, oldAccess);
      end ;
      Inc(pitd_org);
      Inc(pitd_1st);
    until  pitd_1st^.Func =  0 ;
    Inc(piid);
  until  piid^.FirstThunk + piid^.OriginalFirstThunk + piid^.ForwarderChain + piid^.Name =  0 ;
end ;

function  GetSkinSBInfo(hWnd: HWND): PSkinSBInfo;
begin
  Result := PSkinSBInfo( GetProp(hWnd, MAKEINTATOM(l_SkinSB_Prop)) );
end ;

function  GetSkinSB: TSkinSB;
begin
  if  l_SkinSB =  nil  then  l_SkinSB := TSkinSB . CreateInstance;
  Result := l_SkinSB;
end ;

function  CalcScrollBarRect(H: HWND; nBarCode:  Cardinal ): TRect;
var
  Style, ExStyle:  Cardinal ;
begin
  SetRect(Result,  0 ,  0 ,  0 ,  0 );
  Style := GetWindowLong(H, GWL_STYLE);
  ExStyle := GetWindowLong(H, GWL_EXSTYLE);
  if  (nBarCode = SB_HORZ)  and  ((Style  and  WS_HSCROLL) =  0 )  then  Exit;
  if  (nBarCode = SB_VERT)  and  ((Style  and  WS_VSCROLL) =  0 )  then  Exit;
  GetWindowRect(H, Result);
  OffsetRect(Result, -Result . Left, -Result . Top);
  if  ((ExStyle  and  WS_EX_DLGMODALFRAME) <>  0 )
    or  ((ExStyle  and  WS_EX_CLIENTEDGE) <>  0 )  then
  begin
    InflateRect(Result, -GetSystemMetrics(SM_CXEDGE), -GetSystemMetrics(SM_CYEDGE));
  end ;
  // special: returns the cross
  if  nBarCode = SB_BOTH  then
  begin
    if  ((Style  and  WS_HSCROLL) =  0 )  or  ((Style  and  WS_VSCROLL) =  0 )  then
    begin
      SetRect(Result,  0 ,  0 ,  0 ,  0 );
      Exit;
    end ;
    Result . Top := Result . Bottom - GetSystemMetrics(SM_CYVSCROLL);
    if  (ExStyle  and  WS_EX_LEFTSCROLLBAR) <>  0  then  Result . Right := Result . Left + GetSystemMetrics(SM_CXHSCROLL)
    else  Result . Left := Result . Right - GetSystemMetrics(SM_CXHSCROLL);
    Exit;
  end ;
  if  nBarCode = SB_HORZ  then
  begin
  //    if (ExStyle and WS_EX_TOPSCROLLBAR) <> 0 then Result.Bottom := Result.Top + GetSystemMetrics(SM_CYVSCROLL)
    Result . Top := Result . Bottom - GetSystemMetrics(SM_CYVSCROLL);
    if  ((Style  and  WS_VSCROLL) <>  0 )  then  Dec(Result . Right, GetSystemMetrics(SM_CYVSCROLL));
  end ;
  if  nBarCode = SB_VERT  then
  begin
    if  (ExStyle  and  WS_EX_LEFTSCROLLBAR) <>  0  then  Result . Right := Result . Left + GetSystemMetrics(SM_CXHSCROLL)
    else  Result . Left := Result . Right - GetSystemMetrics(SM_CXHSCROLL);
    if  ((Style  and  WS_HSCROLL) <>  0 )  then  Dec(Result . Bottom, GetSystemMetrics(SM_CXHSCROLL));
  end ;
end ;

type
  TBarElem = (beArrow1, beBG, beThumb, beArrow2);
  TBarElemRects =  array [TBarElem]  of  TRect;

function  CalcBarElemRects(hWnd: HWND; nBarCode:  Integer ): TBarElemRects;
var
  R: TRect;
  SI: TScrollInfo;
  ThumbSize:  Integer ;
  X, L, H, BlockH, BlockV:  Integer ;
begin
  R := CalcScrollBarRect(hWnd, nBarCode);
  SI . cbSize := SizeOf(SI);
  SI . fMask := SIF_ALL;
  GetScrollInfo(hWnd, nBarCode, SI);
  Result[beArrow1] := R;
  Result[beArrow2] := R;
  Result[beBG] := R;
  Result[beThumb] := R;
  if  nBarCode = SB_VERT  then
  begin
    BlockV := GetSystemMetrics(SM_CYVSCROLL);
    L := Result[beArrow1].Top + BlockV;
    H := Result[beArrow2].Bottom - BlockV;
    Result[beArrow1].Bottom := L;
    Result[beArrow2].Top := H;
//    Inc(L);
//    Dec(H);
    Result[beBG].Top := L;
    Result[beBG].Bottom := H;
  end
  else
  begin
    BlockH := GetSystemMetrics(SM_CXHSCROLL);
    L := Result[beArrow1].Left + BlockH;
    H := Result[beArrow2].Right - BlockH;
    Result[beArrow1].Right := L;
    Result[beArrow2].Left := H;
//    Inc(L);
//    Dec(H);
    Result[beBG].Left := L;
    Result[beBG].Right := H;
  end ;
  if  SI . nMax - SI . nMin -  Integer (SI . nPage) +  1  <=  0  then
  begin
    // max thumb, no thumb
    if  nBarCode = SB_VERT  then
    begin
      Result[beThumb].Top := L;
      Result[beThumb].Bottom := H;
    end
    else
    begin
      Result[beThumb].Left := L;
      Result[beThumb].Right := H;
    end ;
    Exit;
  end ;
  ThumbSize := MulDiv(H - L, SI . nPage, SI . nMax - SI . nMin +  1 );
  X := L + MulDiv(SI . nTrackPos, H - ThumbSize - L, SI . nMax -  Integer (SI . nPage) - SI . nMin +  1 );
  if  nBarCode = SB_VERT  then
  begin
    Result[beThumb].Top := X;
    Result[beThumb].Bottom := X + ThumbSize;
  end
  else
  begin
    Result[beThumb].Left := X;
    Result[beThumb].Right := X + ThumbSize;
  end ;
end ;

function  GetPtBarPos(H: HWND; Pt: TPoint): TBarPosCode;
var
  R: TRect;
  BR: TBarElemRects;
begin
  Result := bpcNone;
  R := CalcScrollBarRect(H, SB_HORZ);
  InflateRect(R, GetSystemMetrics(SM_CXEDGE), GetSystemMetrics(SM_CYEDGE));
  if  PtInRect(R, Pt)  then
  begin
    BR := CalcBarElemRects(H, SB_HORZ);
    if  PtInRect(BR[beArrow1], Pt)  then  Result := bpcHArrowL
    else  if  PtInRect(BR[beThumb], Pt)  then  Result := bpcHThumb
    else  if  PtInRect(BR[beArrow2], Pt)  then  Result := bpcHArrowR
    else  if  Pt . X < BR[beThumb].Left  then  Result := bpcHPageL
    else  Result := bpcHPageR;
    Exit;
  end ;
  R := CalcScrollBarRect(H, SB_VERT);
  InflateRect(R, GetSystemMetrics(SM_CXEDGE), GetSystemMetrics(SM_CYEDGE));
  if  PtInRect(R, Pt)  then
  begin
    BR := CalcBarElemRects(H, SB_VERT);
    if  PtInRect(BR[beArrow1], Pt)  then  Result := bpcVArrowU
    else  if  PtInRect(BR[beThumb], Pt)  then  Result := bpcVThumb
    else  if  PtInRect(BR[beArrow2], Pt)  then  Result := bpcVArrowD
    else  if  Pt . Y < BR[beThumb].Top  then  Result := bpcVPageU
    else  Result := bpcVPageD;
    Exit;
  end ;
end ;

type
  TGetScrollInfoFunc =  function  (H: HWND; Code:  Integer ;  var  SI: TScrollInfo):  Boolean ; stdcall;

function  _SkinSB_GetScrollInfo(H: HWND; Code:  Integer ;  var  SI: TScrollInfo):  Boolean ; stdcall;
var
  P: PSkinSBInfo;
begin
  Result := TGetScrollInfoFunc(_HookGetScrollInfo . OldFunc)(H, Code, SI);
  P := GetSkinSBInfo(H);
  if  (P <>  nil )  and  P^.ThumbTrack  and  ((SI . fMask  and  SIF_TRACKPOS) <>  0 )  then
  begin
    SI . nTrackPos := P^.ThumbPos;
  end ;
end ;

{ TSkinSB }

constructor  TSkinSB . Create;
begin
  raise  Exception . Create( 'use GetSkinSB.' );
end ;

constructor  TSkinSB . CreateInstance;
begin
  inherited ;
  _HookGetScrollInfo . OldFunc :=  nil ;
  _HookGetScrollInfo . NewFunc := @_SkinSB_GetScrollInfo;
  HookApiInMod( GetModuleHandle( 'comctl32.dll' ),  'GetScrollInfo' , @_HookGetScrollInfo );
  FBitmap := TBitmap . Create;
  FBitmap . LoadFromResourceName(hInstance,  'scrollbar' );
end ;

destructor  TSkinSB . Destroy;
begin
  FreeAndNil(FBitmap);
  inherited ;
end ;

procedure  TSkinSB . DrawElem(H: HWND; Code: TBarPosCode; R: TRect;
  Down:  Boolean );
var
  Canvas: TCanvas;
begin
  Canvas := TCanvas . Create;
  try
    Canvas . Handle := GetWindowDC(H);
    try
      case  Code  of
        bpcHArrowL:
        begin
          if  Down  then  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  64 ,  0 , SRCCOPY)
          else  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  0 ,  0 , SRCCOPY);
          Exit;
        end ;
        bpcHArrowR:
        begin
          if  Down  then  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  80 ,  0 , SRCCOPY)
          else  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  16 ,  0 , SRCCOPY);
          Exit;
        end ;
        bpcHThumb:
        begin
          BitBlt(Canvas . Handle, R . Left, R . Top,  2 ,  16 , FBitmap . Canvas . Handle,  128 ,  0 , SRCCOPY);
          BitBlt(Canvas . Handle, R . Right -  2 , R . Top,  2 ,  16 , FBitmap . Canvas . Handle,  142 ,  0 , SRCCOPY);
          StretchBlt(Canvas . Handle, R . Left +  2 , R . Top, R . Right - R . Left -  4 ,  16 , FBitmap . Canvas . Handle,
            130 ,  0 ,  12 ,  16 , SRCCOPY);
          Exit;
        end ;
        bpcHPageL, bpcHPageR:
        begin
          if  R . Right - R . Left <  4  then
          begin
            StretchBlt(Canvas . Handle, R . Left, R . Top, R . Right - R . Left,  16 , FBitmap . Canvas . Handle,
              160 ,  0 ,  16 ,  16 , SRCCOPY);
          end
          else
          begin
            BitBlt(Canvas . Handle, R . Left, R . Top,  2 ,  16 , FBitmap . Canvas . Handle,  160 ,  0 , SRCCOPY);
            BitBlt(Canvas . Handle, R . Right -  2 , R . Top,  2 ,  16 , FBitmap . Canvas . Handle,  174 ,  0 , SRCCOPY);
            StretchBlt(Canvas . Handle, R . Left +  2 , R . Top, R . Right - R . Left -  4 ,  16 , FBitmap . Canvas . Handle,
              162 ,  0 ,  12 ,  16 , SRCCOPY);
          end ;
          Exit;
        end ;
        bpcVArrowU:
        begin
          if  Down  then  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  96 ,  0 , SRCCOPY)
          else  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  32 ,  0 , SRCCOPY);
          Exit;
        end ;
        bpcVArrowD:
        begin
          if  Down  then  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  112 ,  0 , SRCCOPY)
          else  BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  16 , FBitmap . Canvas . Handle,  48 ,  0 , SRCCOPY);
          Exit;
        end ;
        bpcVThumb:
        begin
          BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  2 , FBitmap . Canvas . Handle,  144 ,  0 , SRCCOPY);
          BitBlt(Canvas . Handle, R . Left, R . Bottom -  2 ,  16 ,  2 , FBitmap . Canvas . Handle,  144 ,  14 , SRCCOPY);
          StretchBlt(Canvas . Handle, R . Left, R . Top +  2 ,  16 , R . Bottom - R . Top -  4 , FBitmap . Canvas . Handle,
            144 ,  2 ,  16 ,  12 , SRCCOPY);
          Exit;
        end ;
        bpcVPageU, bpcVPageD:
        begin
          if  R . Bottom - R . Top <  4  then
          begin
            StretchBlt(Canvas . Handle, R . Left, R . Top,  16 , R . Bottom - R . Top, FBitmap . Canvas . Handle,
              176 ,  0 ,  16 ,  16 , SRCCOPY);
          end
          else
          begin
            BitBlt(Canvas . Handle, R . Left, R . Top,  16 ,  2 , FBitmap . Canvas . Handle,  176 ,  0 , SRCCOPY);
            BitBlt(Canvas . Handle, R . Left, R . Bottom -  2 ,  16 ,  2 , FBitmap . Canvas . Handle,  176 ,  14 , SRCCOPY);
            StretchBlt(Canvas . Handle, R . Left, R . Top +  2 ,  16 , R . Bottom - R . Top -  4 , FBitmap . Canvas . Handle,
              176 ,  2 ,  16 ,  12 , SRCCOPY);
          end ;
          Exit;
        end ;
      end ;
      Canvas . Pen . Color := clBlack;
      Canvas . Brush . Color := clWhite;
      Canvas . Rectangle(R);
    finally
      ReleaseDC(H, Canvas . Handle);
    end ;
  finally
    Canvas . Handle :=  0 ;
    FreeAndNil(Canvas);
  end ;
end ;

procedure  TSkinSB . InitSkinSB(H: HWND);
var
  PInfo: PSkinSBInfo;
begin
  PInfo := GetSkinSBInfo(H);
  if  PInfo <>  nil  then  Exit;  // already inited
  New(PInfo);
  PInfo^.OldWndProc := TWindowProc(GetWindowLong(H, GWL_WNDPROC));
  PInfo^.Style := GetWindowLong(H, GWL_STYLE);
  PInfo^.Prevent :=  False ;
  PInfo^.Scrolling :=  False ;
  PInfo^.ThumbTrack :=  False ;
  SetWindowLong(H, GWL_WNDPROC,  Cardinal (@SkinSBWndProc));
  SetProp(H, MAKEINTATOM(l_SkinSB_Prop),  Cardinal (PInfo));
end ;

procedure  TSkinSB . UnInitSkinSB(H: HWND);
var
  PInfo: PSkinSBInfo;
begin
  PInfo := GetSkinSBInfo(H);
  if  PInfo =  nil  then  Exit;  // not inited
  RemoveProp(H, MAKEINTATOM(l_SkinSB_Prop));
  SetWindowLong(H, GWL_WNDPROC,  Cardinal (@PInfo^.OldWndProc));
  Dispose(PInfo);
end ;

const
  WM_REPEAT_CLICK = WM_USER +  $6478 ;

procedure  OnRepeatClickTimer(hWnd: HWND; uMsg: UINT; idEvent: UINT; dwTime: DWORD); stdcall;
begin
  KillTimer( 0 , idEvent);
  PostThreadMessage(MainThreadID, WM_REPEAT_CLICK,  0 ,  0 );
end ;

procedure  RedrawScrollBars(hWnd: HWND);
var
  RHBar, RVBar, RCross: TRect;
  BR: TBarElemRects;
begin
  RHBar := CalcScrollBarRect(hWnd, SB_HORZ);
  if  not  IsRectEmpty(RHBar)  then
  begin
    BR := CalcBarElemRects(hWnd, SB_HORZ);
    GetSkinSB . DrawElem(hWnd, bpcHPageL, Rect(BR[beBG].Left, BR[beBG].Top, BR[beThumb].Left, BR[beBG].Bottom),  False );
    GetSkinSB . DrawElem(hWnd, bpcHPageR, Rect(BR[beThumb].Right, BR[beBG].Top, BR[beBG].Right, BR[beBG].Bottom),  False );
    GetSkinSB . DrawElem(hWnd, bpcHThumb, BR[beThumb],  False );
    GetSkinSB . DrawElem(hWnd, bpcHArrowL, BR[beArrow1],  False );
    GetSkinSB . DrawElem(hWnd, bpcHArrowR, BR[beArrow2],  False );
  end ;
  RVBar := CalcScrollBarRect(hWnd, SB_VERT);
  if  not  IsRectEmpty(RVBar)  then
  begin
    BR := CalcBarElemRects(hWnd, SB_VERT);
    GetSkinSB . DrawElem(hWnd, bpcVPageU, Rect(BR[beBG].Left, BR[beBG].Top, BR[beBG].Right, BR[beThumb].Top),  False );
    GetSkinSB . DrawElem(hWnd, bpcVPageD, Rect(BR[beBG].Left, BR[beThumb].Bottom, BR[beBG].Right, BR[beBG].Bottom),  False );
    GetSkinSB . DrawElem(hWnd, bpcVThumb, BR[beThumb],  False );
    GetSkinSB . DrawElem(hWnd, bpcVArrowU, BR[beArrow1],  False );
    GetSkinSB . DrawElem(hWnd, bpcVArrowD, BR[beArrow2],  False );
  end ;
  RCross := CalcScrollBarRect(hWnd, SB_BOTH);
  if  not  IsRectEmpty(RCross)  then
  begin
    GetSkinSB . DrawElem(hWnd, bpcCross, RCross,  False );
  end ;
end ;

procedure  TrackBar(hWnd: HWND; nBarCode:  Integer ; PosCode: TBarPosCode; BarElem: TBarElem; MsgCode:  Integer );
var
  BR: TBarElemRects;
  Msg: tagMSG;
  Pt: TPoint;
  R: TRect;
  ScrollMsg:  Cardinal ;
  RepeatClick:  Boolean ;
  idEvent: UINT;
  SI: TScrollInfo;

  procedure  RefreshRect;
  begin
    BR := CalcBarElemRects(hWnd, nBarCode);
    R := BR[BarElem];
  end ;

begin
  RepeatClick :=  False ;
  BR := CalcBarElemRects(hWnd, nBarCode);
  R := BR[BarElem];
  GetScrollInfo(hWnd, nBarCode, SI);
  if  nBarCode = SB_HORZ  then  ScrollMsg := WM_HSCROLL
  else  ScrollMsg := WM_VSCROLL;
  if  BarElem = beBG  then
  begin
    if  PosCode = bpcHPageL  then  R . Right := BR[beThumb].Left
    else  if  PosCode = bpcHPageR  then  R . Left := BR[beThumb].Right
    else  if  PosCode = bpcVPageU  then  R . Bottom := BR[beThumb].Top
    else  if  PosCode = bpcVPageD  then  R . Top := BR[beThumb].Bottom;
  end ;
  GetSkinSB . DrawElem(hWnd, PosCode, R,  True );
  GetSkinSBInfo(hWnd)^.Tracking :=  True ;
  idEvent :=  0 ;
  try
    SetCapture(hWnd);
    idEvent := SetTimer( 0 ,  0 ,  1000 , @OnRepeatClickTimer);
    while  GetCapture = hWnd  do
    begin
      if  not  GetMessage(Msg,  0 ,  0 ,  0 )  then  Break;
      if  (Msg . hwnd =  0 )  and  (Msg . message = WM_REPEAT_CLICK)  then
      begin
        GetCursorPos(Pt);
        ScreenToClient(hWnd, Pt);
        if  PtInRect(R, Pt)  then
        begin
          RepeatClick :=  True ;
          SendMessage(hWnd, ScrollMsg, MsgCode,  0 );
          SendMessage(hWnd, ScrollMsg, SB_ENDSCROLL,  0 );
          RefreshRect;
          GetSkinSB . DrawElem(hWnd, PosCode, R,  True );
//          if MsgCode = SB_LINEDOWN then SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) + 1, False);
          if  MsgCode = SB_PAGEDOWN  then  SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) +  Integer (SI . nPage),  False );
//          if MsgCode = SB_LINEUP then SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) - 1, False);
          if  MsgCode = SB_PAGEUP  then  SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) -  Integer (SI . nPage),  False );
          RedrawScrollBars(hWnd);
          SetTimer( 0 ,  0 ,  80 , @OnRepeatClickTimer);
        end ;
      end
      else  if  Msg . hwnd = hWnd  then
      begin
        case  Msg . message  of
          WM_LBUTTONUP:
          begin
            if  RepeatClick  then  Break;
            GetCursorPos(Pt);
            ScreenToClient(hWnd, Pt);
            if  PtInRect(R, Pt)  then
            begin
              SendMessage(hWnd, ScrollMsg, MsgCode,  0 );
              SendMessage(hWnd, ScrollMsg, SB_ENDSCROLL,  0 );
              RefreshRect;
//              if MsgCode = SB_LINEDOWN then SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) + 1, False);
              if  MsgCode = SB_PAGEDOWN  then  SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) +  Integer (SI . nPage),  False );
//              if MsgCode = SB_LINEUP then SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) - 1, False);
              if  MsgCode = SB_PAGEUP  then  SetScrollPos(hWnd, nBarCode, GetScrollPos(hWnd, nBarCode) -  Integer (SI . nPage),  False );
            end ;
            Break;
          end ;
        end ;
      end ;
      DispatchMessage(Msg);
    end ;
  finally
    if  idEvent <>  0  then  KillTimer( 0 , idEvent);
    if  IsWindow(hWnd)  then
    begin
      if  GetCapture = hWnd  then  ReleaseCapture;
      GetSkinSB . DrawElem(hWnd, PosCode, R,  False );
      GetSkinSBInfo(hWnd)^.Tracking :=  False ;
    end ;
  end ;
end ;

procedure  TrackThumb(hWnd: HWND; nBarCode:  Integer ; PosCode: TBarPosCode; BarElem: TBarElem);
var
  BR: TBarElemRects;
  Msg: tagMSG;
  Pt: TPoint;
  DragX:  Integer ;
  R: TRect;
  ScrollMsg:  Cardinal ;
  SI, SI2: TScrollInfo;
  Pos:  Integer ;
  H, L, ThumbSize, X:  Integer ;
  Pushed:  Boolean ;

  function  ValidDragArea(ARect: TRect; APt: TPoint):  Boolean ;
  begin
    if  nBarCode = SB_HORZ  then  Result :=  Abs ((ARect . Bottom + ARect . Top)  div  2  - APt . Y) <  150
    else  Result :=  Abs ((ARect . Left + ARect . Right)  div  2  - APt . X) <  150 ;
  end ;

  function  CalcPos(ARect: TRect; APt: TPoint; ADragX:  Integer ):  Integer ;
  var
    NewX:  Integer ;
  begin
    if  nBarCode = SB_HORZ  then  NewX := APt . X - ADragX
    else  NewX := APt . Y - ADragX;
    Result := SI . nMin + MulDiv(NewX - L, SI . nMax -  Integer (SI . nPage) - SI . nMin +  1 , H - L - ThumbSize);
    if  Result < SI . nMin  then  Result := SI . nMin;
    if  Result > SI . nMax -  Integer (SI . nPage) +  1  then
      Result := SI . nMax -  Integer (SI . nPage) +  1 ;
  end ;

  procedure  UpdateDragBar(ADown:  Boolean ; APos:  Integer  = - 10000 );
  var
    W:  Integer ;
  begin
    BR := CalcBarElemRects(hWnd, nBarCode);
    R := BR[BarElem];
    if  nBarCode = SB_HORZ  then
    begin
      if  APos <> - 10000  then
      begin
        W := R . Right - R . Left;
        if  APos < BR[beArrow1].Right  then  APos := BR[beArrow1].Right;
        if  APos + W > BR[beArrow2].Left  then  APos := BR[beArrow2].Left - W;
        R . Left := APos;
        R . Right := APos + W;
      end ;
      GetSkinSB . DrawElem(hWnd, bpcHPageL, Rect(BR[beBG].Left, BR[beBG].Top, R . Left, BR[beBG].Bottom),  False );
      GetSkinSB . DrawElem(hWnd, bpcHPageR, Rect(R . Right, BR[beBG].Top, BR[beBG].Right, BR[beBG].Bottom),  False );
    end
    else
    begin
      if  APos <> - 10000  then
      begin
        W := R . Bottom - R . Top;
        if  APos < BR[beArrow1].Bottom  then  APos := BR[beArrow1].Bottom;
        if  APos + W >= BR[beArrow2].Top  then  APos := BR[beArrow2].Top - W -  1 ;
        R . Top := APos;
        R . Bottom := APos + W;
      end ;
      GetSkinSB . DrawElem(hWnd, bpcVPageU, Rect(BR[beBG].Left, BR[beBG].Top, BR[beBG].Right, R . Top),  False );
      GetSkinSB . DrawElem(hWnd, bpcVPageD, Rect(BR[beBG].Left, R . Bottom, BR[beBG].Right, BR[beBG].Bottom),  False );
    end ;
    GetSkinSB . DrawElem(hWnd, PosCode, R, ADown);
    OutputDebugString( PChar (Format( 'R=(%d,%d,%d,%d)' , [R . Left, R . Top, R . Right, R . Bottom])));
  end ;

begin
  BR := CalcBarElemRects(hWnd, nBarCode);
  R := BR[BarElem];
  if  nBarCode = SB_HORZ  then  ScrollMsg := WM_HSCROLL
  else  ScrollMsg := WM_VSCROLL;
  SI . cbSize := SizeOf(SI);
  SI . fMask := SIF_ALL;
  GetScrollInfo(hWnd, nBarCode, SI);
  GetCursorPos(Pt);
  ScreenToClient(hWnd, Pt);
  if  nBarCode = SB_HORZ  then
  begin
    DragX := Pt . X - BR[beThumb].Left;
    ThumbSize := BR[beThumb].Right - BR[beThumb].Left;
    L := BR[beArrow1].Right;
    H := BR[beArrow2].Left;
  end
  else
  begin
    DragX := Pt . Y - BR[beThumb].Top;
    ThumbSize := BR[beThumb].Bottom - BR[beThumb].Top;
    L := BR[beArrow1].Bottom;
    H := BR[beArrow2].Top;
  end ;
{  if nBarCode = SB_HORZ then SendMessage(hWnd, WM_SYSCOMMAND, SC_HSCROLL, MAKELPARAM(Pt.X, Pt.Y))
  else SendMessage(hWnd, WM_SYSCOMMAND, SC_VSCROLL, MAKELPARAM(Pt.X, Pt.Y)); }
  GetSkinSBInfo(hWnd)^.Tracking :=  True ;
  UpdateDragBar( True );
  try
    SetCapture(hWnd);
    while  GetCapture = hWnd  do
    begin
      if  not  GetMessage(Msg,  0 ,  0 ,  0 )  then  Break;
      if  Msg . hwnd = hWnd  then
      begin
        case  Msg . message  of
          WM_MOUSEMOVE:
          begin
            Pushed := ValidDragArea(R, Pt);
            GetCursorPos(Pt);
            ScreenToClient(hWnd, Pt);
            if  ValidDragArea(R, Pt)  then
            begin
              Pos := CalcPos(R, Pt, DragX);
              if  nBarCode = SB_HORZ  then  X := Pt . X - DragX
              else  X := Pt . Y - DragX;
            end
            else
            begin
              Pos := SI . nPos;
              X := DragX;
            end ;
            GetSkinSBInfo(hWnd)^.ThumbPos := Pos;
            GetSkinSBInfo(hWnd)^.ThumbTrack :=  True ;
            SendMessage(hWnd, ScrollMsg, MAKEWPARAM(SB_THUMBTRACK, Pos),  0 );
            GetSkinSBInfo(hWnd)^.ThumbTrack :=  False ;
            UpdateDragBar(Pushed, X);
          end ;
          WM_LBUTTONUP:
          begin
            GetCursorPos(Pt);
            ScreenToClient(hWnd, Pt);
            if  ValidDragArea(R, Pt)  then
            begin
              Pos := CalcPos(R, Pt, DragX);
              SI2 . cbSize := SizeOf(SI2);
              SI2 . fMask := SIF_ALL;
              GetScrollInfo(hWnd, nBarCode, SI2);
              SI2 . nPos := Pos;
              SI2 . nTrackPos := Pos;
              SetScrollInfo(hWnd, nBarCode, SI2,  False );
              SI2 . nTrackPos :=  0 ;
              SI2 . nPos :=  0 ;
              GetScrollInfo(hWnd, nBarCode, SI2);
              SendMessage(hWnd, ScrollMsg, MAKEWPARAM(SB_THUMBPOSITION, Pos),  0 );
              SendMessage(hWnd, ScrollMsg, SB_ENDSCROLL,  0 );
            end ;
            Break;
          end ;
        end ;
      end ;
      DispatchMessage(Msg);
    end ;
  finally
    if  IsWindow(hWnd)  then
    begin
      if  GetCapture = hWnd  then  ReleaseCapture;
      GetSkinSBInfo(hWnd)^.Tracking :=  False ;
    end ;
    UpdateDragBar( False );
  end ;
end ;

function  SkinSBWndProc(hWnd: HWND; uMsg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT;
var
  PInfo: PSkinSBInfo;
  Style, ExStyle:  Cardinal ;
  R, RHBar, RVBar, RCross: TRect;
  Pt: TPoint;
  Rgn, Rgn2: HRGN;
  PR: PRect;
  BR: TBarElemRects;
  XBar, YBar:  Integer ;
begin
  PInfo := GetSkinSBInfo(hWnd);
  if  PInfo =  nil  then  Result := DefWindowProc(hWnd, uMsg, wParam, lParam)  //// error!!!
  else
  begin
    case  uMsg  of
      WM_NCHITTEST:
      begin
        GetCursorPos(Pt);
        ScreenToClient(hWnd, Pt);
        case  GetPtBarPos(hWnd, Pt)  of
          bpcHArrowL:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackBar(hWnd, SB_HORZ, bpcHArrowL, beArrow1, SB_LINELEFT);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcHArrowR:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackBar(hWnd, SB_HORZ, bpcHArrowR, beArrow2, SB_LINERIGHT);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcHPageL:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
              begin
                TrackBar(hWnd, SB_HORZ, bpcHPageL, beBG, SB_PAGELEFT);
                RedrawScrollBars(hWnd);
              end ;
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcHPageR:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
              begin
                TrackBar(hWnd, SB_HORZ, bpcHPageR, beBG, SB_PAGERIGHT);
                RedrawScrollBars(hWnd);
              end ;
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcHThumb:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackThumb(hWnd, SB_HORZ, bpcHThumb, beThumb);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;

          bpcVArrowU:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackBar(hWnd, SB_VERT, bpcVArrowU, beArrow1, SB_LINELEFT);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcVArrowD:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackBar(hWnd, SB_VERT, bpcVArrowD, beArrow2, SB_LINERIGHT);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcVPageU:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
              begin
                TrackBar(hWnd, SB_VERT, bpcVPageU, beBG, SB_PAGELEFT);
                RedrawScrollBars(hWnd);
              end ;
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcVPageD:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
              begin
                TrackBar(hWnd, SB_VERT, bpcVPageD, beBG, SB_PAGERIGHT);
                RedrawScrollBars(hWnd);
              end ;
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
          bpcVThumb:
          begin
            if  (GetKeyState(VK_LBUTTON)  and  $8000 ) <>  0  then
            begin
              if  GetCapture <> hWnd  then
                TrackThumb(hWnd, SB_VERT, bpcVThumb, beThumb);
            end ;
            Result := HTNOWHERE;
            Exit;
          end ;
        end ;
      end ;
      WM_HSCROLL:
      begin
        PInfo^.Scrolling :=  True ;
        Style := GetWindowLong(hWnd, GWL_STYLE);
        PInfo^.Style := Style;
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style  and  ( not  (WS_VSCROLL  or  WS_HSCROLL)));
        finally
          PInfo^.Prevent :=  False ;
        end ;
        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
        RedrawScrollBars(hWnd);
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style);
        finally
          PInfo^.Prevent :=  False ;
        end ;
        PInfo^.Scrolling :=  False ;
        Exit;
      end ;

      WM_VSCROLL:
      begin
        PInfo^.Scrolling :=  True ;
        Style := GetWindowLong(hWnd, GWL_STYLE);
        PInfo^.Style := Style;
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style  and  ( not  (WS_VSCROLL  or  WS_HSCROLL)));
        finally
          PInfo^.Prevent :=  False ;
        end ;
        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style);
        finally
          PInfo^.Prevent :=  False ;
        end ;
        PInfo^.Scrolling :=  False ;
        Exit;
      end ;
      WM_STYLECHANGED:
      begin
        if  wParam = GWL_STYLE  then
        begin
          if  PInfo^.Prevent  then
          begin
            Result :=  0 ;
            Exit;
          end
          else
          begin
            PInfo^.Style := GetWindowLong(hWnd, GWL_STYLE);
          end ;
        end ;
      end ;
      WM_NCCALCSIZE:
      begin
        Style := GetWindowLong(hWnd, GWL_STYLE);
        ExStyle := GetWindowLong(hWnd, GWL_EXSTYLE);
        XBar := GetSystemMetrics(SM_CXVSCROLL);
        YBar := GetSystemMetrics(SM_CYHSCROLL);
        if  PInfo^.Scrolling  then
        begin
          PInfo^.Prevent :=  True ;
          try
            SetWindowLong(hWnd, GWL_STYLE, Style  and  ( not  (WS_HSCROLL  or  WS_VSCROLL)));   // real style
          finally
            PInfo^.Prevent :=  False ;
          end ;
        end ;
        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
        if  PInfo^.Scrolling  then
        begin
          PR := PRect(lParam);
          if  (PInfo^.Style  and  WS_VSCROLL) <>  0  then
          begin
            if  (ExStyle  and  WS_EX_LEFTSCROLLBAR) <>  0  then  Inc(PR^.Left, XBar)
            else  Dec(PR^.Right, XBar);
          end ;
          if  (PInfo^.Style  and  WS_HSCROLL) <>  0  then
          begin
            Dec(PR^.Bottom, YBar);
          end ;
        end ;
        if  PInfo^.Scrolling  then
        begin
          PInfo^.Prevent :=  True ;
          try
            SetWindowLong(hWnd, GWL_STYLE, Style);   // old style
          finally
            PInfo^.Prevent :=  False ;
          end ;
        end ;
        Exit;
      end ;
      WM_NCPAINT:
      begin
        GetWindowRect(hWnd, R);
        Pt := R . TopLeft;
        if  wParam =  1  then
        begin
          Rgn := CreateRectRgn(Pt . X, Pt . Y, Pt . X + R . Right, Pt . Y + R . Bottom);
        end  else  Rgn := wParam;
        RHBar := CalcScrollBarRect(hWnd, SB_HORZ);
        OffsetRect(RHBar, Pt . X, PT . Y);
        if  not  IsRectEmpty(RHBar)  then
        begin
          BR := CalcBarElemRects(hWnd, SB_HORZ);
          GetSkinSB . DrawElem(hWnd, bpcHPageL, Rect(BR[beBG].Left, BR[beBG].Top, BR[beThumb].Left, BR[beBG].Bottom),  False );
          GetSkinSB . DrawElem(hWnd, bpcHPageR, Rect(BR[beThumb].Right, BR[beBG].Top, BR[beBG].Right, BR[beBG].Bottom),  False );
          GetSkinSB . DrawElem(hWnd, bpcHThumb, BR[beThumb],  False );
          GetSkinSB . DrawElem(hWnd, bpcHArrowL, BR[beArrow1],  False );
          GetSkinSB . DrawElem(hWnd, bpcHArrowR, BR[beArrow2],  False );
        end ;
        Rgn2 := CreateRectRgn(RHBar . Left, RHBar . Top, RHBar . Right, RHBar . Bottom);
        CombineRgn(Rgn, Rgn, Rgn2, RGN_DIFF);
        DeleteObject(Rgn2);
        RVBar := CalcScrollBarRect(hWnd, SB_VERT);
        if  not  IsRectEmpty(RVBar)  then
        begin
          BR := CalcBarElemRects(hWnd, SB_VERT);
          GetSkinSB . DrawElem(hWnd, bpcVPageU, Rect(BR[beBG].Left, BR[beBG].Top, BR[beBG].Right, BR[beThumb].Top),  False );
          GetSkinSB . DrawElem(hWnd, bpcVPageD, Rect(BR[beBG].Left, BR[beThumb].Bottom, BR[beBG].Right, BR[beBG].Bottom),  False );
          GetSkinSB . DrawElem(hWnd, bpcVThumb, BR[beThumb],  False );
          GetSkinSB . DrawElem(hWnd, bpcVArrowU, BR[beArrow1],  False );
          GetSkinSB . DrawElem(hWnd, bpcVArrowD, BR[beArrow2],  False );
        end ;
        OffsetRect(RVBar, Pt . X, PT . Y);
        Rgn2 := CreateRectRgn(RVBar . Left, RVBar . Top, RVBar . Right, RVBar . Bottom);
        CombineRgn(Rgn, Rgn, Rgn2, RGN_DIFF);
        DeleteObject(Rgn2);
        RCross := CalcScrollBarRect(hWnd, SB_BOTH);
        if  not  IsRectEmpty(RCross)  then
        begin
          GetSkinSB . DrawElem(hWnd, bpcCross, RCross,  False );
        end ;
        OffsetRect(RCross, Pt . X, PT . Y);
        Rgn2 := CreateRectRgn(RCross . Left, RCross . Top, RCross . Right, RCross . Bottom);
        CombineRgn(Rgn, Rgn, Rgn2, RGN_DIFF);
        DeleteObject(Rgn2);
        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, Rgn, lParam);
        if  wParam =  1  then  DeleteObject(Rgn);
        Exit;
      end ;
      WM_ERASEBKGND:
      begin
        Style := GetWindowLong(hWnd, GWL_STYLE);
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style  and  ( not  (WS_VSCROLL  or  WS_HSCROLL)));
        finally
          PInfo^.Prevent :=  False ;
        end ;

        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
        PInfo^.Prevent :=  True ;
        try
          SetWindowLong(hWnd, GWL_STYLE, Style);   // old style
        finally
          PInfo^.Prevent :=  False ;
        end ;
        Exit;
      end ;
      WM_MOUSEWHEEL, WM_MOUSEMOVE:
      begin
        Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
        if  PInfo^.Tracking  then  Exit;
        if  (uMsg = WM_MOUSEMOVE)  and  ((wParam  and  MK_LBUTTON) =  0 )  then  Exit;
        RedrawScrollBars(hWnd);
        Exit;
      end ;
    end ;
    Result := CallWindowProc(@PInfo^.OldWndProc, hWnd, uMsg, wParam, lParam);
  end ;
end ;

initialization

  l_SkinSB :=  nil ;
  l_SkinSB_Prop := GlobalAddAtom(SKINSB_PROP);

finalization

  if  Assigned(l_SkinSB)  then  FreeAndNil(l_SkinSB);

end .

补充：使用此方法后，在调用SetScrollInfo后也必须调用RedrawScrollBars重绘滚动条。Hook本模块的SetScrollInfo API是个好方法。在这里就不给出代码了。

学习中的点点滴滴予以记载，以便以后的学习复习。 本篇博客转自Lucky2011的博客(http://www.cnblogs.com/Lucky2011/)

http://www.cnblogs.com/Lucky2011/archive/2011/04/01/2002131.html

 

关于ListView 设置OwnerData 为 True时 Items删除节点不起作用

当ListView 设置OwnerData := True 时，再调用ListView.Items.delete(I)，是不起作用的。

在使用很多方法和查询资料的方法的也没有解决这个问题。

但是在我仔细研究listView源码后发现可以利用消息的方法删除某个节点，SendMessage(hWnd, LVM_DELETEITEM, i, 0);

在CommCtrl单元里面封装好了对listView的所有消息的的接口；

本例用到的接口如下：

function ListView_DeleteItem(hWnd: HWND; i: Integer): Bool;

学习中的点点滴滴予以记载，以便以后的学习复习。 本篇博客转自Lucky2011的博客(http://www.cnblogs.com/Lucky2011/)

 

http://www.cnblogs.com/Lucky2011/archive/2011/04/06/2006554.html