You can trap the OnMouseDown event, remembering the x and y coordinates of the mouse and set the mouse capture. You can then track mouse movements with the OnMouseMove event, moving the control until the OnMouseUp event is fired. You then will want to place the control in it's final position and release capture of the mouse.

The following example shows how to move a TButton component around on the form using the mouse. The movement is initiated by the user holding down the control key when the mouse button is activated.

Example:

type TForm = class(TForm) Button : TButton; procedure Button MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); procedure Button MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer); procedure Button MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); private { Private declarations } public { Public declarations } MouseDownSpot : TPoint; Capturing : bool; end;

var Form : TForm ;

implementation

{$R *.DFM}

procedure TForm .Button MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); begin if ssCtrl in Shift then begin SetCapture(Button .Handle); Capturing := true; MouseDownSpot.X := x; MouseDownSpot.Y := Y; end; end;

procedure TForm .Button MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer); begin if Capturing then begin Button .Left := Button .Left - (MouseDownSpot.x - x); Button .Top := Button .Top - (MouseDownSpot.y - y); end; end;

procedure TForm .Button MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); begin if Capturing then begin ReleaseCapture; Capturing := false; Button .Left := Button .Left - (MouseDownSpot.x - x); Button .Top := Button .Top - (MouseDownSpot.y - y); end; end;

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