Пример компонента HotSpot

Вот пример HotSpot-компонента, основанного на TPanel (небольшая переделка). Управляя событиями MouseDown и MouseUp можно получить эффект резинового контура.

unit Newpanel;
 
interface
uses WinTypes, Classes, Controls, StdCtrls, ExtCtrls;
 
type
 
  tHotSpotClickEvent = procedure(Sender: tObject;
    Button: tMouseButton;
    Shift: tShiftState) of object;
 
  TNewPanel = class(tPanel)
  private
    fHotSpotClick: tHotSpotClickEvent;
    fHotSpot: tRect;
    fInHotSpot: Boolean;
    function GetHotSpotTop: Word;
    function GetHotSpotLeft: Word;
    function GetHotSpotWidth: Word;
    function GetHotSpotHeight: Word;
    procedure SetHotSpotTop(Value: Word);
    procedure SetHotSpotLeft(Value: Word);
    procedure SetHotSpotWidth(Value: Word);
    procedure SetHotSpotHeight(Value: Word);
  protected
    procedure Paint; override;
    procedure MouseDown(Button: tMouseButton; Shift: tShiftState; X, Y: Integer);
      override;
    procedure MouseUp(Button: tMouseButton; Shift: tShiftState; X, Y: Integer);
      override;
  public
    procedure Click; override;
    property HotSpot: tRect read fHotSpot write fHotSpot;
  published
    property hsTop: Word read GetHotSpotTop write SetHotSpotTop;
    property hsLeft: Word read GetHotSpotLeft write SetHotSpotLeft;
    property hsWidth: Word read GetHotSpotWidth write SetHotSpotWidth;
    property hsHeight: Word read GetHotSpotHeight write SetHotSpotHeight;
    property OnHotSpot: tHotSpotClickEvent read fHotSpotClick write
      fHotSpotClick;
  end;
 
procedure Register;
 
implementation
uses WinProcs, Graphics;
 
procedure Register;
begin
  RegisterComponents('Custom', [TNewPanel]);
end;
 
procedure TNewPanel.MouseDown(Button: tMouseButton;
  Shift: tShiftState;
  X, Y: Integer);
begin
  if PtInRect(fHotSpot, Point(X, Y)) and
    Assigned(fHotSpotClick) then
    fInHotSpot := True;
  inherited MouseDown(Button, Shift, X, Y);
end;
 
procedure TNewPanel.MouseUp(Button: tMouseButton;
  Shift: tShiftState;
  X, Y: Integer);
begin
  inherited MouseUp(Button, Shift, X, Y);
 
  if fInHotSpot then
  begin
    if Assigned(fHotSpotClick) then
      fHotSpotClick(Self, Button, Shift);
    fInHotSpot := False;
  end;
end;
 
procedure TNewPanel.Click;
begin
  if not fInHotSpot then
    inherited Click;
end;
 
procedure TNewPanel.Paint;
var
  OldStyle: tPenStyle;
begin
  inherited Paint;
 
  if csDesigning in ComponentState then
  begin
    OldStyle := Canvas.Pen.Style;
    Canvas.Pen.Style := psDash;
    Canvas.Rectangle(HotSpot.Left, HotSpot.Top, HotSpot.Right, HotSpot.Bottom);
    Canvas.Pen.Style := OldStyle;
  end;
end;
 
procedure TNewPanel.SetHotSpotTop(Value: Word);
begin
  fHotSpot.Bottom := fHotSpot.Bottom + Value - fHotSpot.Top;
  fHotSpot.Top := Value;
  Paint;
end;
 
procedure TNewPanel.SetHotSpotLeft(Value: Word);
begin
  fHotSpot.Right := fHotSpot.Right + Value - fHotSpot.Left;
  fHotSpot.Left := Value;
  Paint;
end;
 
procedure TNewPanel.SetHotSpotWidth(Value: Word);
begin
  fHotSpot.Right := fHotSpot.Left + Value;
  Paint;
end;
 
procedure TNewPanel.SetHotSpotHeight(Value: Word);
begin
  fHotSpot.Bottom := fHotSpot.Top + Value;
  Paint;
end;
 
function TNewPanel.GetHotSpotTop: Word;
begin
  Result := fHotSpot.Top
end;
 
function TNewPanel.GetHotSpotLeft: Word;
begin
  Result := fHotSpot.Left;
end;
 
function TNewPanel.GetHotSpotWidth: Word;
begin
  Result := fHotSpot.Right - fHotSpot.Left;
end;
 
function TNewPanel.GetHotSpotHeight: Word;
begin
  Result := fHotSpot.Bottom - fHotSpot.Top;
end;
 
end.

Автор: Robert Wittig

Взято с https://delphiworld.narod.ru