Creating and registering Delphi components.
Notes from Richard.
There are various aspects to this, but here we have an example that does things
in perhaps the most simple way. The program below is complete and should be used
like this: in the example we don't create a new 'object' from scratch (which we
COULD do) -here we change the behaviour of an existing object. We define our own
OwnerDrawRichEdit object to be a descendant of the RichEdit component, and we say
in effect 'everything you do is fine except for things to do with a WMPaint message'
so we REdefine that here.
Having defined our new object, and spelled out the new procedure in a program, we
add a new special procedure to the end called Register, with one line that says
RegisterComponents('RichEbbs', [TOwnerDrawRichEdit]);
so that now when we run this program we have a special .dcu (component definition)
file among the other compiled files. From Delphi's IDE choose Component and Install
and ADD THE PATH TO THIS DCU FILE TO THE EXISTING PATH (ie put a semicolon at the
end of the the existing pathand then add the rest) and continue the procedure to
ADD your new component to the IDE component pallette. Then choose Rebuild Library
and lo and behold your new component has it's own tab and you can drag it across
the desktop like any other. Wow!
**************************************************************************
unit RegUnit;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls, ComCtrls;
type
TOwnerDrawRichEdit = class(TRichEdit)
private
{private declarations}
procedure WMPaint(var Message: TWMPaint); message WM_PAINT;
protected
{protected declarations}
public
{public declarations}
published
{published declarations}
end;
procedure Register;
implementation
procedure TOwnerDrawRichEdit.WMPaint(var Message: TWMPaint);
var
Buffer: Array[0..255] of Char;
PS: TPaintStruct;
DC: HDC;
i: Integer;
X,Y,Z: Word;
OldColor: LongInt;
begin
DC := Message.DC;
if DC = 0 then DC := BeginPaint(Handle, PS);
try
X := 1;
Y := 1;
SetBkColor(DC, Color);
SetBkMode(DC, Transparent);
OldColor := Font.Color;
for i:=0 to Pred(Lines.Count) do
begin
if odd(i) then SetTextColor(DC, clRed)
else SetTextColor(DC, OldColor);
Z := Length(Lines[i]);
StrPCopy(Buffer, Lines[i]);
Buffer[Z] := #0; { not really needed }
TextOut(DC, X,Y, Buffer, Z);
Inc(Y, abs(Font.Height));
end;
finally
if Message.DC = 0 then EndPaint(Handle, PS);
end;
end;
procedure Register;
begin
RegisterComponents('RichEbbs', [TOwnerDrawRichEdit]);
end;
end.