Autocomplete TEdit

http://forum.codecall.net/topic/75946-autocomplete-tedit/ 

Overview 

Autocomplete feature really helpful for us speeding up our typing job.

For you who is not familiar with the term autocomplete,

it's when you type partial part of a word and then

you will be presented with a list of possible complete words.

You can just select the correct word from the list,

and that partial word will be automatically completed.

In programming, this feature very helpful to

"remember" class names, routine names, and variable name. 

Not only to speed up the typing, autocomplete also very helpful to avoid typo. 

In this tutorial I will show you a technique to implement autocomplete

in your Delphi program in order to provide your users the benefits of autocomplete.

I will implement autocomplete in a descendant of TEdit. I name it TAutocompleteEdit. 

TAutoCompleteEdit

Behaviors

1. Upon typing some chars, TAutocompleteEdit will check the typed word agains a word list. When no match found, do nothing.
2. When one or more matches found, TAutocompleteEdit show the matches in a TListBox.We will call this TListBoxWordList.
3. User can move between TAutocompleteEdit and WordList using down and up arrow.
4. User select a complete word from WordList by highlighting the word and press Enter key.
5. After user selected a word, the word will replace whatever content in TAutocompleteEdit.
6. If user press Escape in TAutocompleteEdit or in WordList, WordList must dissapear.
7. If TAutocompleteEdit lost focus, and the new focus is not in WordList, WordList must dissapear.
8. If WordList lost focus, and the new focus is not in TAutocompleteEdit, WordList must dissapear.
9. If later user type in another character and no match found, WordList must dissapear. 

Key Methods 

From the above behaviors, we decided to have the following methods.

1. ShowWordList(AWords: TStrings).
   This method is responsible to create WordList TListBox when needed,
   populate it with words contained in AWords, and
   also to patch its events so we can achieve behavior #3, #4, #5, #6, and #8.
2. HideWordList.
   This method is responsible to hide and clean up WordList.
3. Change.
   This is where to respond when the content of TAutocompleteEdit changed.
   So this is where we do the checking.
   This method actually already exist in TAutocompleteEdit's parent.
   So what we are going to do is override it, and introduce our behavior.
4. DoExit.
   This method also already exist in TAutocompleteEdit's parent.
   We are going to override it and introduce new behavior, in order to achieve behavior #7.
5. KeyDown(var Key: Word; Shift: TShiftState).
   This method also already exist in TAutocompleteEdit's parent.
   We are going to override it to achieve behavior #3 and #6. 

Key Methods Implementations 

1. ShowWordList(AWords: TStrings).

 
 
procedure TAutocompleteEdit.ShowWordList(AWords: TStrings);
begin
  if FWordList=nil then
  begin
    FWordList := TListBox.Create(Self);
    FWordList.ParentCtl3D := False;
    FWordList.Ctl3D := False;
    FWordList.Parent := Self.Parent;
    FWordList.TabStop := False;
    FWordList.OnExit := HandleWordListLostFocus;
    FWordList.OnKeyPress := HandleWordListKeyPress;
    FWordList.OnKeyDown := HandleWordListKeyDown;
  end;
 
  FWordList.Items.Assign(AWords);
  if FWordListWidth < 1 then
    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, Self.Width, FWordListHeight)
  else
    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, FWordListWidth, FWordListHeight);
 
  FWordList.Show;
end;
 

 2. HideWordList

 
procedure TAutocompleteEdit.HideWordList;
begin
  PostMessage(Self.Handle, MSG_HIDEWORDLIST, 0, 0);
end;

 Note that in the above method we only post a custom message. The custom message handler in turn will call this private method. 

procedure TAutocompleteEdit.HandleHideWordList;
begin
  FWordList.Free;
  FWordList := nil;
end;

 3. Change.

procedure TAutocompleteEdit.Change;
var
  S: TStrings;
begin
  inherited;
  if AutocompleteMan.IsRecognized(Self.Text) then
  begin
    S := TStringList.Create;
    try
      if AutocompleteMan.IsRecognized(Self.Text, S) then
        ShowWordList(S);
    finally
      S.Free;
    end;
  end
  else
    HideWordList;
end;

 4. DoExit.

procedure TAutocompleteEdit.DoExit;
begin
  if Assigned(FWordList) and FWordList.Visible and not FWordList.Focused then
    HideWordList;
  inherited;
end;

5. KeyDown(var Key: Word; Shift: TShiftState). 

 
procedure TAutocompleteEdit.KeyDown(var Key: Word; Shift: TShiftState);
begin
  if Key=VK_ESCAPE then
    HideWordList
  else if (Key=VK_DOWN) and Assigned(FWordList) and FWordList.Visible then
  begin
    FCaretPos := Self.SelStart;
    FWordList.SetFocus;
    if FWordList.ItemIndex < 0 then
      FWordList.ItemIndex := 0;
  end
  else
    inherited;
end;

Here is the complete source code of TAutocompleteEdit: 

TEdit with Autocomplete.zip   1.84MB   603 downloads.

Feel free to use it or improve it for any kind of use. 

Cheers!

unit AutocompleteEdit;

interface

uses
  Windows
  , Classes
  , Vcl.StdCtrls
  , SysUtils
  , StrUtils
  , Messages
  ;

const
  MSG_HIDEWORDLIST = WM_USER + 222;

type
  TAutocompleteEdit=class(TEdit)
  private
    FWordList: TListBox;
    FCaretPos: Integer;
    FWordListHeight: Integer;
    FWordListWidth: Integer;

    procedure HandleWordListLostFocus(ASender: TObject);
    procedure HandleWordListSelectItem(ASender: TObject);
    procedure HandleWordListKeyPress(Sender: TObject; var Key: Char);
    procedure HandleWordListKeyDown(ASender: TObject; var Key: Word; Shift: TShiftState);
    procedure HandleHideWordList(var AMsg); overload; message MSG_HIDEWORDLIST;
    procedure HandleHideWordList; overload;
    procedure SetWordListHeight(const Value: Integer);
    procedure SetWordListWidth(const Value: Integer);

    procedure RegainFocus;
  protected
    procedure ShowWordList(AWords: TStrings);
    procedure HideWordList;
    procedure Change; override;
    procedure KeyDown(var Key: Word; Shift: TShiftState); override;
    procedure DoExit; override;
  public
    constructor Create(AOwner: TComponent); override;
  published
    property WordListHeight: Integer read FWordListHeight write SetWordListHeight;
    property WordListWidth: Integer read FWordListWidth write SetWordListWidth;
  end;

  TAutocompleteMan=class
  private
    FWords: TStrings;
  public
    constructor Create;
    destructor Destroy; override;

    function IsRecognized(AWord: string): Boolean; overload;
    function IsRecognized(AWord: string; AWordList: TStrings): Boolean; overload;

    procedure LoadFromFile(const AFilename: string);
    procedure AddWord(const AWord: string);

    property Words: TStrings read FWords;
  end;

  procedure Register;

var
  AutocompleteMan: TAutocompleteMan;


implementation

procedure Register;
begin
  RegisterComponents('CodeCall', [TAutocompleteEdit]);
end;

{ TAutocompleteMan }

procedure TAutocompleteMan.AddWord(const AWord: string);
begin
  FWords.Add(UpperCase(AWord) + '=' + AWord);
end;

constructor TAutocompleteMan.Create;
begin
  FWords := TStringList.Create;
  TStringList(FWords).Duplicates := dupIgnore;
end;

destructor TAutocompleteMan.Destroy;
begin
  FWords.Free;
  inherited;
end;

function TAutocompleteMan.IsRecognized(AWord: string): Boolean;
var
  i: Integer;
begin
  Result := False;
  AWord := UpperCase(AWord);
  for i := 0 to FWords.Count-1 do
  begin
    Result := System.Pos(AWord, FWords.Names[i]) > 0;
    if Result then
      Break;
  end;
end;

function TAutocompleteMan.IsRecognized(AWord: string;
  AWordList: TStrings): Boolean;
var
  i: Integer;
begin
  Result := False;
  AWord := UpperCase(AWord);
  AWordList.Clear;
  for i := 0 to FWords.Count-1 do
  begin
    if System.Pos(AWord, FWords.Names[i]) > 0 then
    begin
      Result := True;
      AWordList.Add(FWords.ValueFromIndex[i]);
    end;
  end;
end;

procedure TAutocompleteMan.LoadFromFile(const AFilename: string);
var
  i: Integer;
  F: TStrings;
begin
  F := TStringList.Create;
  try
    F.LoadFromFile(AFilename);
    for i := 0 to F.Count-1 do
      AddWord(F[i]);
  finally
    F.Free;
  end;
end;

{ TAutocompleteEdit }

procedure TAutocompleteEdit.Change;
var
  S: TStrings;
begin
  inherited;
  if AutocompleteMan.IsRecognized(Self.Text) then
  begin
    S := TStringList.Create;
    try
      if AutocompleteMan.IsRecognized(Self.Text, S) then
        ShowWordList(S);
    finally
      S.Free;
    end;
  end
  else
    HideWordList;
end;

procedure TAutocompleteEdit.HandleHideWordList(var AMsg);
begin
  HandleHideWordList;
end;

constructor TAutocompleteEdit.Create(AOwner: TComponent);
begin
  inherited;
  FWordListHeight := 60;
end;

procedure TAutocompleteEdit.DoExit;
begin
  if Assigned(FWordList) and FWordList.Visible and not FWordList.Focused then
    HideWordList;
  inherited;
end;

procedure TAutocompleteEdit.HandleHideWordList;
begin
  FWordList.Free;
  FWordList := nil;
end;

procedure TAutocompleteEdit.HandleWordListKeyDown(ASender: TObject;
  var Key: Word; Shift: TShiftState);
begin
  if (Key=VK_UP) and (FWordList.ItemIndex=0) then
    RegainFocus;
end;

procedure TAutocompleteEdit.HandleWordListKeyPress(Sender: TObject;
  var Key: Char);
begin
  case Key of
    #13: begin
           Key := #0;
           Self.Text := FWordList.Items[FWordList.ItemIndex];
           Self.SetFocus;
           Self.SelStart := Length(Self.Text);
           Self.SelLength := 0;
           HideWordList;
         end;
    #27: begin
           RegainFocus;
           HideWordList;
         end;
    else begin
      RegainFocus;
    end;
  end;
end;

procedure TAutocompleteEdit.HandleWordListLostFocus(ASender: TObject);
begin
  if not Self.Focused then
    HideWordList;
end;

procedure TAutocompleteEdit.HandleWordListSelectItem(ASender: TObject);
begin
  Self.Text := FWordList.Items[FWordList.ItemIndex];
  HideWordList;
end;

procedure TAutocompleteEdit.HideWordList;
begin
  PostMessage(Self.Handle, MSG_HIDEWORDLIST, 0, 0);
end;

procedure TAutocompleteEdit.KeyDown(var Key: Word; Shift: TShiftState);
begin
  if Key=VK_ESCAPE then
    HideWordList
  else if (Key=VK_DOWN) and Assigned(FWordList) and FWordList.Visible then
  begin
    FCaretPos := Self.SelStart;
    FWordList.SetFocus;
    if FWordList.ItemIndex < 0 then
      FWordList.ItemIndex := 0;
  end
  else
    inherited;
end;

procedure TAutocompleteEdit.RegainFocus;
begin
  Self.SetFocus;
  Self.SelStart := FCaretPos;
  Self.SelLength := 0;
end;

procedure TAutocompleteEdit.SetWordListHeight(const Value: Integer);
begin
  if FWordListHeight <> Value then
  begin
    FWordListHeight := Value;
    if Assigned(FWordList) then
      FWordList.Height := FWordListHeight;
  end;
end;

procedure TAutocompleteEdit.SetWordListWidth(const Value: Integer);
begin
  if FWordListWidth <> Value then
  begin
    FWordListWidth := Value;
    if Assigned(FWordList) then
    begin
      if FWordListWidth < 1 then
        FWordList.Width := Self.Width
      else
        FWordList.Width := FWordListWidth;
    end;
  end;
end;

procedure TAutocompleteEdit.ShowWordList(AWords: TStrings);
begin
  if FWordList=nil then
  begin
    FWordList := TListBox.Create(Self);
    FWordList.ParentCtl3D := False;
    FWordList.Ctl3D := False;
    FWordList.Parent := Self.Parent;
    FWordList.TabStop := False;
    FWordList.OnExit := HandleWordListLostFocus;
    FWordList.OnKeyPress := HandleWordListKeyPress;
    FWordList.OnKeyDown := HandleWordListKeyDown;
  end;

  FWordList.Items.Assign(AWords);
  if FWordListWidth < 1 then
    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, Self.Width, FWordListHeight)
  else
    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, FWordListWidth, FWordListHeight);

  FWordList.Show;
end;

initialization
  AutocompleteMan := TAutocompleteMan.Create;

finalization
  AutocompleteMan.Free;
end.