Creating and Registering the Graphic Component

You create every component in the same way: create a unit, derive a component class, register it, compile it, and install it on the Tool palette. This process is outlined in Creating a new component.

For this example, follow the general procedure for creating a component, with these specifics:

Call the component's unit Shapes.
Derive a new component type called TSampleShape, descended from TGraphicControl.
Register TSampleShape on the Samples category of the Tool palette.

The resulting unit should look like this:

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unit Shapes;
interface
uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms;
type
  TSampleShape = class(TGraphicControl)
  end;
procedure Register;
implementation
procedure Register;
begin
  RegisterComponent('Samples', [TSampleShape]);
end;
end.

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//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Shapes.h"
//---------------------------------------------------------------------------
#pragma package(smart_init);
//---------------------------------------------------------------------------
// ValidCtrCheck is used to assure that the components created do not have
// any pure virtual functions.
//
static inline void ValidCtrCheck(TSampleShape *)
{
  new TSampleShape(NULL);
}
//---------------------------------------------------------------------------
__fastcall TSampleShape::TGraphicControl(TComponent* Owner)
: TGraphicControl(Owner)
{
}
//---------------------------------------------------------------------------
namespace Shapes
{
  void __fastcall PACKAGE Register()
  {
    TComponentClass classes[1] = {__classid(TSampleShape)};
    RegisterComponents("Samples", classes, 0);
  }
}

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//---------------------------------------------------------------------------
#ifndef ShapesH
#define ShapesH
//---------------------------------------------------------------------------
#include <sysutils.hpp>
#include <controls.hpp>
#include <classes.hpp>
#include <forms.hpp>
//---------------------------------------------------------------------------
class PACKAGE TSampleShape : public TGraphicControl
{
private:
protected:
public:
__published:
};
//---------------------------------------------------------------------------
#endif

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