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unit MyDragButton;

interface

uses
  SysUtils, Classes, Controls, StdCtrls, Graphics, Types, QControls;

type
  TMyDragButton = class(TButton)
  private
    FDragImages: TDragImageList;
  protected
    function GetDragImages: TDragImageList; override;
    procedure MouseDown(Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer); override;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  published
    { Published declarations }
  end;

procedure Register;

implementation


constructor TMyDragButton.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ControlStyle := ControlStyle + [csDisplayDragImage];
end;

destructor TMyDragButton.Destroy;
begin
  FDragImages.Free;
  inherited;
end;

function TMyDragButton.GetDragImages: TDragImageList;
var
  Bmp: TBitmap;
  BmpIdx: Integer;
  Pt: TPoint;
begin
  if not Assigned(FDragImages) then
    FDragImages := TDragImageList.Create(Self);
  Bmp := TBitmap.Create;
  try
    Bmp.Width := Width;
    Bmp.Height := Height;
    Bmp.Canvas.Lock;
    try
      PaintTo(Bmp.Canvas.Handle, 0, 0);
    finally
      Bmp.Canvas.Unlock
    end;
    FDragImages.Width := Width;
    FDragImages.Height := Height;
    BmpIdx := FDragImages.AddMasked(Bmp, clBtnFace);
    //Where is mouse relative to control?
    GetCursorPos(Pt);
    Pt := ScreenToClient(Pt);
    //Specify drag image and hot spot
    FDragImages.SetDragImage(BmpIdx, Pt.X, Pt.Y);
    Result := FDragImages;
  finally
    Bmp.Free
  end
end;

procedure TDragButton.MouseDown(Button: TMouseButton; Shift: TShiftState;
  X, Y: Integer);
begin
  inherited;
  //Automatically start dragging on a Ctrl-click
  if ssCtrl in Shift then
    BeginDrag(True)
end;

procedure Register;
begin
  RegisterComponents('Samples', [TMyDragButton]);
end;

end.                    

1:

procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer); override;                    

1:

ontrolStyle := ControlStyle + [csDisplayDragImage];