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library GraphicControls;

uses
  SysUtils,
  Windows,
  Messages,
  Classes;

function SetHook:Boolean; export; forward;
procedure UnHook; export; forward;
procedure SetWindowHandle(WindowHandle: HWND); export; forward;
function HookProc(nCode: Integer; WPARAM: wParam; LPARAM: lParam):LResult; stdcall; forward;

exports
  SetHook index 1,
  UnHook index 2,
  SetWindowHandle index 3;

var H: HWND = 0;
    HookID: HHook;

function SetHook:Boolean;
begin
  HookID := SetWindowsHookEx(WH_MOUSE, @HookProc, hInstance, 0);
  if HookID <> 0 then
    Result := True
  else
    Result := False;
end;

procedure Unhook;
begin
  UnHookWindowsHookEx(HookID);
end;

procedure SetWindowHandle(WindowHandle: HWND);
begin
  H := WindowHandle;
end;

function HookProc(nCode: Integer; WPARAM: wParam; LPARAM: lParam): LResult; stdcall;
begin
  if nCode >= 0 then begin
    SendMessage(H, WM_MOUSEMOVE, WPARAM, LPARAM);
    Result := CallNextHookEx(WH_MOUSE, nCode, wParam, lParam);
  end
  else
    Result := CallNextHookEx(WH_MOUSE, nCode, wParam, lParam);
end;
[/code]

auszug aus meiner komponente (ich möchte hier nicht den ganzen quellcode zeigen):

[code]

type THoverButton = class(TCustomControl)
 ...
 ...   

implementation

function SetHook:Boolean; external 'C:\Programme\Borland\Delphi7\Lib\GraphicControls.dll';
procedure UnHook; external 'C:\Programme\Borland\Delphi7\Lib\GraphicControls.dll';
procedure SetWindowHandle(WindowHandle: HWND); external 'C:\Programme\Borland\Delphi7\Lib\GraphicControls.dll';
 
 ...

procedure THoverButton.SetParent(AParent: TWinControl);
begin
  inherited;
  if csDesigning in ComponentState then exit;
  ....
  ....
  if not FHooked then begin
    SetWindowHandle(Handle);
    SetHook;
    FHooked := True;
  end;
end;

 ...

constructor THoverButton.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  //Initialize variables
  ControlStyle := [csOpaque, csReplicatable, csDoubleClicks, csCaptureMouse, csClickEvents];
  ...
  FHooked := False;
end;

destructor THoverButton.Destroy;
begin
  // Free up resources
  ....
  inherited Destroy;
  if FHooked then Unhook;
end;					

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type THoverButton = class(TCustomControl)
    ....
   procedure MouseLeavesTheForm(var m: TMessage);
    ....
end;

.....

procedure THoverButton.MouseLeavesTheForm(var m: TMessage);
begin
  inherited;
  ....
  FisTracking := False;
  m.Result := 1;
end;

....

procedure THoverButton.WMMouseMove(var Msg: TWMMouseMove);
begin
  inherited;
  if not FisTracking then begin
    TrackMouseEvent(FevtTrack);
    FisTracking := True;
  end;
end;

....

procedure THoverButton.SetParent(AParent: TWinControl);
begin
  inherited;
  if csDesigning in ComponentState then exit;
  if AParent <> nil then begin
  with FevtTrack do begin
    cbSize := sizeOf(tagTRACKMOUSEEVENT);
    dwFlags := TME_LEAVE;
    hwndTrack := Handle;
    dwHoverTime := HOVER_DEFAULT;
  end;
end;