need help with component....

hi,

this a component i created
but there are some errors in it.
can you please look at it and
give your input on it.

TIA, ruben

the code is :

*** Start of Code ***

unit ExtMemo;

interface

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

type
TExtMemo = class(TCustomMemo)
private
  { Private declarations }
  FManualInvoke : Boolean;
  FPopup: Boolean; (* changes *)
  FAutoComplete : Boolean;
  FMinLength : Integer;
  FOptions : TStringList;
  FOptionsListBox : TListBox;
protected
  { Protected declarations }
  function CurrentWord:String;
  procedure Change; override;
  procedure KeyDown(var Key: Word; Shift: TShiftState); override;
  procedure KeyPress(var Key: Char); override;
  procedure SetParent(AParent: TWinControl); override;
public
  { Public declarations }
  constructor Create(AOwner: TComponent); override;
  destructor Destroy; override;
  property Options : TStringList read FOptions write FOptions;
published
  { Published declarations }
  property AutoComplete : Boolean read FAutoComplete write FAutoComplete;
  property AutoCompLength : Integer read FMinLength write FMinLength;
  //property's of TMemo
  property Align;
  property Alignment;
  property Anchors;
  property BiDiMode;
  property BorderStyle;
  property Color;
  property Constraints;
  property Ctl3D;
  property DragCursor;
  property DragKind;
  property DragMode;
  property Enabled;
  property Font;
  property HideSelection;
  property ImeMode;
  property ImeName;
  property Lines;
  property MaxLength;
  property OEMConvert;
  property ParentBiDiMode;
  property ParentColor;
  property ParentCtl3D;
  property ParentFont;
  property ParentShowHint;
  property PopupMenu;
  property ReadOnly;
  property ScrollBars;
  property ShowHint;
  property TabOrder;
  property TabStop;
  property Visible;
  property WantReturns;
  property WantTabs;
  property WordWrap;
  property OnChange;
  property OnClick;
  property OnContextPopup;
  property OnDblClick;
  property OnDragDrop;
  property OnDragOver;
  property OnEndDock;
  property OnEndDrag;
  property OnEnter;
  property OnExit;
  property OnKeyDown;
  property OnKeyPress;
  property OnKeyUp;
  property OnMouseDown;
  property OnMouseMove;
  property OnMouseUp;
  property OnStartDock;
  property OnStartDrag;
end;

procedure Register;

implementation

function TExtMemo.CurrentWord: String;
var
  FPos : Integer;
begin
  FPos := CaretPos.x;
  while (not(Lines[CaretPos.y][FPos] in [' ','.',','])) and (FPos > 0) do Dec(FPos);
  Inc(FPos);
  Result := Copy(Lines[CaretPos.y], FPos, CaretPos.x - FPos + 1); (* changes *)
end;

procedure TExtMemo.SetParent(AParent: TWinControl); (* changes *)
begin
  inherited SetParent(AParent);
  FOptionsListBox.Parent := AParent;
end;

procedure TExtMemo.Change; (* changes *)
var
  i     : Integer;
  {FPos  : Integer; //Position of Char    }
  FWord : String;  //Current Word
  FFirstVisible : LongInt;
  TextSize : TSize;
  FCanvas: TCanvas;
begin
  inherited;
  FOptionsListBox.Visible := False;
  FOptionsListBox.Clear;
  if (CaretPos.x > 0) and not (Lines[CaretPos.y][CaretPos.x] in [' ','.',',']) then
  begin
    FWord := CurrentWord;
    if (FAutoComplete and (Length(FWord) >= FMinLength)) or FPopup then
    begin
     for i := 0 to FOptions.Count - 1 do
       if Length(FOptions.Strings[i]) > Length(FWord) then
         if AnsiCompareText(Copy(FOptions.Strings[i], 1, Length(FWord)), FWord) = 0 then
           FOptionsListBox.Items.Add(FOptions.Strings[i]);
    end;
  end;
  if FPopup then FPopup := False;
  if FOptionsListBox.Items.Count > 0 then
  begin
    FOptionsListBox.Visible := True;
    FOptionsListBox.ItemIndex := 0;
    FFirstVisible := SendMessage(Self.Handle, EM_GETFIRSTVISIBLELINE, 0, 0);
    FCanvas := TCanvas.Create;
    try
      FCanvas.Handle := GetDC(Self.Handle);
      TextSize.cx := 0;
      if (CaretPos.x - Length(FWord)) > 0
       then TextSize := FCanvas.TextExtent(Copy(Lines[CaretPos.y], 1, CaretPos.x - Length(FWord)))
       else TextSize.cy := FCanvas.TextHeight('X');
    finally
     FCanvas.Free;
    end;
    if (TextSize.cx + FOptionsListBox.Width) > Self.ClientWidth
     then FOptionsListBox.Left := (Self.ClientWidth - FOptionsListBox.Width) -2
     else FOptionsListBox.Left := TextSize.cx + 2;
    if ((TextSize.cy * CaretPos.y) + FOptionsListBox.Height) > Self.ClientHeight
      then FOptionsListBox.Top := (TextSize.cy * (CaretPos.y - FFirstVisible)) - FOptionsListBox.Height
      else FOptionsListBox.Top := (TextSize.cy * (CaretPos.y - FFirstVisible + 1)) + 2; {(CaretPos.y - FFirstVisible + 1) * TextSize.cy;}
  end;
end;

procedure TExtMemo.KeyDown(var Key: Word; Shift: TShiftState);
begin
  inherited;
  if FOptionsListBox.Visible and (Key in [VK_DOWN, VK_UP, VK_ESCAPE]) then
  begin
    case Key of
      VK_DOWN   : if FOptionsListBox.ItemIndex < FOptionsListBox.Items.Count then
                    FOptionsListBox.ItemIndex := FOptionsListBox.ItemIndex + 1;
      VK_UP     : if FOptionsListBox.ItemIndex > 0 then
                    FOptionsListBox.ItemIndex := FOptionsListBox.ItemIndex - 1;
      VK_ESCAPE : FOptionsListBox.Visible := False;
    end;
    Key := 0;
  end else
    if (ssCtrl in Shift) and (Key = VK_SPACE) then
    begin
      FManualInvoke := True;
      FPopup := True; (* changes *)
      Key := 0;
      Change; (* changes *)
    end;
end;

procedure TExtMemo.KeyPress(var Key: Char);
var
  FWord : String;  //Current Word
begin
  inherited;
  if FOptionsListBox.Visible and (Key = #13) then
  begin
    if (CaretPos.x > 0) and (Lines[CaretPos.y][CaretPos.x] <> ' ') then
      FWord := CurrentWord;
    SelStart := SelStart - Length(FWord);
    SelLength := Length(FWord);
    SelText := FOptionsListBox.Items[FOptionsListBox.itemindex];
    // !!! JACCO: This was intended to keep capitalisation as user typed
    //SelText := SelText + Copy(FOptionsListBox.Items[FOptionsListBox.itemindex], Length(SelText) + 1,255);
    Key := #0;
  end;
  if FManualInvoke then
  begin
    Key := #0;
    FManualInvoke := False; (* changes *)
  end;
end;

constructor TExtMemo.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FMinLength := 2;
  FAutoComplete := True;
  FOptions := TStringList.Create;
  FOptionsListBox := TListBox.Create(Self); (* changes *)
//  FOptionsListBox.Parent := Self;
  FOptionsListBox.Height := 75;
  FOptionsListBox.Width := 100;
  FOptionsListBox.Visible := False;
end;

destructor TExtMemo.Destroy;
begin
  FOptions.Free;
  FOptionsListBox.Free;
  inherited Destroy;
end;

procedure Register;
begin
  RegisterComponents('SoSsA', [TExtMemo]);
end;

end.


*** End of Code ***
LVL 1
rtielandAsked:
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TOndrejConnect With a Mentor Commented:
I think the problem is in the constructor and SetParent methods.
First, you create the listbox and pass it Self as Owner. This is not necessary if you're managing its lifetime; it's cleaner to pass nil in this case.

Another actual problem is that you don't set the Parent and then you adjust Height, Width and Visible properties. OTTOMH, (some of) these operations require a valid Parent.

From the code it's not clear what you're trying to do...
Do you want the listbox to be child of the memo?
It looks as if you wanted it to be a child of the memo's parent (a form, for example). In that case, you may want to check for csDesigning in ComponentState and avoid creating the listbox at designtime.

In any case, a better place to create/destroy the listbox would be CreateWnd/DestroyWnd (after/before inherited call, respectively). In the constructor your memo doesn't yet have a handle; in the destructor the handle has already been released.

HTH
0
 
Dennis9Commented:
Hi.
Is the error in the source??? or when component is installed?

The only thing i could find was this:
   // !!! JACCO: This was intended to keep capitalisation as user typed
   //SelText := SelText + Copy(FOptionsListBox.Items[FOptionsListBox.itemindex], Length(SelText) +
1,255);

//If it did not have to be used it should be:
   // !!! JACCO: This was intended to keep capitalisation as user typed
 {SelText := SelText + Copy(FOptionsListBox.Items[FOptionsListBox.itemindex], Length(SelText) +
1,255);}

Dennis
0
 
JaccoCommented:
Hi Ruben,

What's wrong with it?

Regards Jacco
0
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rtielandAuthor Commented:
if i register the component in  the component pallet and then create a new application and drop it on the form it gets an error about can't read address 00000
0
 
kretzschmarCommented:
you should check, if your foptionlistpox is assigned generally.

i guess the error comes from

procedure TExtMemo.SetParent(AParent: TWinControl); (* changes *)
begin
 inherited SetParent(AParent);
 FOptionsListBox.Parent := AParent;
end;

change this code to

procedure TExtMemo.SetParent(AParent: TWinControl); (* changes *)
begin
 inherited SetParent(AParent);
 If Assigned(FOptionsListBox) Then
   FOptionsListBox.Parent := AParent;
end;

meikl ;-)

0
 
rtielandAuthor Commented:
this is the exact error
"access violation at address 000000000. read of address 000000000."
kretzschmar : i try'd your comment, doesn't help.
could you guy's try it yourself.

TIA,
ruben
0
 
kretzschmarCommented:
can you show your overridden constructor?
0
 
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