unit ComboBoxAF; //ComboBox AutoFill

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TComboBoxAF = class(TComboBox)
  private
    { Private-Deklarationen }
    FAutoFill : Boolean;
    FLastKey : word;
    FOnKeyDown : TKeyEvent;
    function GetLastKey : word;
    procedure SetLastKey(key : word);
    function GetAutoFill : Boolean;
    procedure SetAutoFill(value : Boolean);
  protected
    { Protected-Deklarationen }
    procedure KeyDown(var Key: Word; Shift: TShiftState); override;
    procedure Change; override;
  public
    { Public-Deklarationen }
    constructor Create(aOwner: TComponent); override;
    Destructor Destroy; override;
    property OnKeyDown : TKeyEvent read FOnKeyDown write FOnKeyDown;
  published
    { Published-Deklarationen }
    property LastKey : word read GetLastKey write SetLastKey;
    property AutoFill : Boolean read GetAutoFill write SetAutoFill;
  end;

procedure Register;

implementation

procedure TComboBoxAF.Change;
var
  srch : string;
  ix : integer;
begin
  if Focused and AutoFill then begin
    srch := Text;
    if LastKey = $08 then begin
      LastKey := 0;
    end
    else begin
      LastKey := 0;
      ix := Perform(CB_FINDSTRING, -1, LongInt(PChar(srch)));
      if ix > CB_ERR then begin
        ItemIndex := ix;
        SelStart := Length(srch);
        SelLength := Length(Text) - length(srch);
      end;
    end;
  end;
  Inherited;
end;

procedure TComboBoxAF.KeyDown(var Key: Word; Shift: TShiftState);
begin
  Inherited; // KeyDown(Key, Shift);
  FLastKey := key;
end;

function TComboBoxAF.GetLastKey : word;
begin
  Result := FLastKey;
end;

procedure TComboBoxAF.SetLastKey(key : word);
begin
  FLastKey := key;
end;

function TComboBoxAF.GetAutoFill : Boolean;
begin
  Result := FAutoFill;
end;

procedure TComboBoxAF.SetAutoFill(value : Boolean);
begin
  FAutoFill := value;
end;

constructor TComboBoxAF.Create(aOwner: TComponent);
begin
  inherited Create(aOwner);
  FLastKey := 0;
  FAutoFill := true;
end;

Destructor TComboBoxAF.Destroy;
Begin
  inherited Destroy;
End;

procedure Register;
begin
  RegisterComponents('Beispiele', [TComboBoxAF]); //
end;

end.

unit FillComboBox;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TFillComboBox = class(TComboBox)
  private
    FAutomaticFillin: Boolean;
    procedure SetAutomaticFillin(const Value: Boolean);
  protected
    procedure ComboWndProc(
      var Message: TMessage; ComboWnd: HWnd; ComboProc: Pointer
    ); override;
  public
  published
    constructor Create(AOwner: TComponent); override;
    property AutomaticFillin: Boolean
      read FAutomaticFillin
      write SetAutomaticFillin
      default True;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Standard', [TFillComboBox]);
end;

{ TFillComboBox } 

procedure TFillComboBox.ComboWndProc(
  var Message: TMessage; ComboWnd: HWnd; ComboProc: Pointer
);
var
  I: Integer;
  CurrentText: String;
begin
  inherited ComboWndProc(Message, ComboWnd, ComboProc);
  // skip processing, if turned off
  if not FAutomaticFillin then
    Exit;
  // first check whether the backspace key was pressed, we do not fill in
  // in such case!
  if Message.Msg = WM_CHAR then
  begin
    // all characters from 32 (Space) through 127 (Upper ANSI) are matched
    if TWMChar(Message).CharCode in [$20..$7F] then
    begin
      // fill in the rest of the text
      // save the current text, the user has typed
      CurrentText := Text;
      // get the first string, matching the text partially
      I := SendMessage(Handle, CB_FINDSTRING, -1, LongInt(PChar(CurrentText)));
      if I >= 0 then
      begin
        // match found!
        // load matching text, I is the position of the matching string
        Text := Items.Strings[I];
        // select the text beyond the text typed
        SelStart := Length(CurrentText);
        SelLength := Length(Text) - Length(CurrentText);
      end;
    end;
  end;
end;

constructor TFillComboBox.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FAutomaticFillin := True;
end;

procedure TFillComboBox.SetAutomaticFillin(const Value: Boolean);
begin
  FAutomaticFillin := Value;
end;

end.