下面这一控件虽不能出现八个点,却能更改大小,你可以参见一下:
unit DdhSizer;
interface
uses
Classes, Windows, Messages, Controls, StdCtrls;
const
sc_DragMove: Longint = $F012;
type
TDdhSizeButton = class (TButton)
public
procedure WmNcHitTest (var Msg: TWmNcHitTest);
message wm_NcHitTest;
end;
TDdhSizerControl = class (TCustomControl)
private
FControl: TControl;
FRectList: array [1..8] of TRect;
FPosList: array [1..8] of Integer;
public
constructor Create (AOwner: TComponent;
AControl: TControl);
procedure CreateParams (var Params: TCreateParams);
override;
procedure CreateHandle; override;
procedure WmNcHitTest (var Msg: TWmNcHitTest);
message wm_NcHitTest;
procedure WmSize (var Msg: TWmSize);
message wm_Size;
procedure WmLButtonDown (var Msg: TWmLButtonDown);
message wm_LButtonDown;
procedure WmMove (var Msg: TWmMove);
message wm_Move;
procedure Paint; override;
procedure SizerControlExit (Sender: TObject);
end;
procedure Register;
implementation
uses
Graphics;
// TDdhSizeButton methods
procedure TDdhSizeButton.WmNcHitTest(var Msg: TWmNcHitTest);
var
Pt: TPoint;
begin
Pt := Point (Msg.XPos, Msg.YPos);
Pt := ScreenToClient (Pt);
if (Pt.x < 5) and (pt.y < 5) then
Msg.Result := htTopLeft
else if (Pt.x > Width - 5) and (pt.y < 5) then
Msg.Result := htTopRight
else if (Pt.x > Width - 5) and (pt.y > Height - 5) then
Msg.Result := htBottomRight
else if (Pt.x < 5) and (pt.y > Height - 5) then
Msg.Result := htBottomLeft
else if (Pt.x < 5) then
Msg.Result := htLeft
else if (pt.y < 5) then
Msg.Result := htTop
else if (Pt.x > Width - 5) then
Msg.Result := htRight
else if (pt.y > Height - 5) then
Msg.Result := htBottom
else
inherited;
end;
// TDdhSizerControl methods
constructor TDdhSizerControl.Create (
AOwner: TComponent; AControl: TControl);
var
R: TRect;
begin
inherited Create (AOwner);
FControl := AControl;
// install the new handler
OnExit := SizerControlExit;
// set the size and position
R := FControl.BoundsRect;
InflateRect (R, 2, 2);
BoundsRect := R;
// set the parent
Parent := FControl.Parent;
// create the list of positions
FPosList [1] := htTopLeft;
FPosList [2] := htTop;
FPosList [3] := htTopRight;
FPosList [4] := htRight;
FPosList [5] := htBottomRight;
FPosList [6] := htBottom;
FPosList [7] := htBottomLeft;
FPosList [8] := htLeft;
end;
procedure TDdhSizerControl.CreateHandle;
begin
inherited CreateHandle;
SetFocus;
end;
procedure TDdhSizerControl.CreateParams (var Params: TCreateParams);
begin
inherited CreateParams(Params);
Params.ExStyle := Params.ExStyle +
ws_ex_Transparent;
end;
procedure TDdhSizerControl.Paint;
var
I: Integer;
begin
Canvas.Brush.Color := clBlack;
for I := 1 to 8 do
Canvas.Rectangle (FRectList .Left, FRectList .Top,
FRectList .Right, FRectList .Bottom);
end;
procedure TDdhSizerControl.WmNcHitTest(var Msg: TWmNcHitTest);
var
Pt: TPoint;
I: Integer;
begin
Pt := Point (Msg.XPos, Msg.YPos);
Pt := ScreenToClient (Pt);
Msg.Result := 0;
for I := 1 to 8 do
if PtInRect (FRectList , Pt) then
Msg.Result := FPosList ;
// if the return value was not set
if Msg.Result = 0 then
inherited;
end;
procedure TDdhSizerControl.WmSize (var Msg: TWmSize);
var
R: TRect;
begin
R := BoundsRect;
InflateRect (R, -2, -2);
FControl.BoundsRect := R;
// setup data structures
FRectList [1] := Rect (0, 0, 5, 5);
FRectList [2] := Rect (Width div 2 - 3, 0,
Width div 2 + 2, 5);
FRectList [3] := Rect (Width - 5, 0, Width, 5);
FRectList [4] := Rect (Width - 5, Height div 2 - 3,
Width, Height div 2 + 2);
FRectList [5] := Rect (Width - 5, Height - 5,
Width, Height);
FRectList [6] := Rect (Width div 2 - 3, Height - 5,
Width div 2 + 2, Height);
FRectList [7] := Rect (0, Height - 5, 5, Height);
FRectList [8] := Rect (0, Height div 2 - 3,
5, Height div 2 + 2);
end;
procedure TDdhSizerControl.SizerControlExit (Sender: TObject);
begin
Free;
end;
procedure TDdhSizerControl.WmLButtonDown (var Msg: TWmLButtonDown);
begin
Perform (wm_SysCommand, sc_DragMove, 0);
end;
procedure TDdhSizerControl.WmMove (var Msg: TWmMove);
var
R: TRect;
begin
R := BoundsRect;
InflateRect (R, -2, -2);
FControl.Invalidate; // repaint entire surface
FControl.BoundsRect := R;
end;
// components registration
procedure Register;
begin
RegisterComponents ('zdl', [TDdhSizeButton]);
RegisterNoIcon ([TDdhSizerControl]);
end;
end.