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。
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。
本文来自Delphi之窗，原文地址：http://www.52delphi.com

//==================================================================
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.