Difference between revisions of "Lazarus Hacks"

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[[Category:Lazarus]]

Revision as of 23:33, 23 January 2013

Add here your hacks modifications to Lazarus IDE or LCL widgets, even if they are not officially accepted maybe if a good idea arise and is good enough it can be part of the official distribution, if not it can be used by other people that need more handy functionality than standards.

Exposing/Extending TCustomEdit

In some applications we need constantly convert TCustomEdit descendants Text property for or to numeric values:

  TCustomEditFilters = (cefNone, cefInteger, cefUnsigned, cefCurrency, cefFloat);

  { TCustomEdit }

  TCustomEdit = class(TWinControl)
  private
    ...
    FTmpModified : Boolean;
    FceFilter : TCustomEditFilters;
    procedure SetceFilter(aCeFilter: TCustomEditFilters);
    function GetAsInteger:Integer;
    procedure SetAsInteger(aVal: Integer);
    function GetAsFloat:Extended;
    procedure SetAsFloat(aVal: Extended);
    function GetAsCurrency:Currency;
    procedure SetAsCurrency(aVal: Currency);

  public
    ...
    property TmpModified: Boolean read FTmpModified write FTmpModified;
    property AsInteger: Integer read getAsInteger write setAsInteger;
    property AsFloat: Extended read getAsFloat write setAsFloat;
    property AsCurrency: Currency read getAsCurrency write setAsCurrency;
  published
    property Alignment: TAlignment read FAlignment write SetAlignment default taLeftJustify;
    property ceFilter : TCustomEditFilters read FceFilter write SetceFilter default cefNone;
  end;

//On the implementation part tcustomedit.inc:

  resourcestring
    rsInvalidNumbe = 'Invalid number !';

  procedure TCustomEdit.Change;
  begin
    FTmpModified := True;
    if Assigned(FOnChange) then FOnChange(Self);
  end;

  procedure TCustomEdit.DoExit;
  begin
    if FCeFilter <> cefNone then
    begin
      case FCeFilter of
        cefInteger, cefUnsigned: AsInteger;
        cefFloat: AsFloat;
        cefCurrency: AsCurrency;
      end;
    end;
    FAutoSelected := False;
    inherited DoExit;
  end;

  procedure TCustomEdit.SetceFilter(aCeFilter: TCustomEditFilters);
  begin
    FCeFilter := aCeFilter;
    if FCeFilter = cefNone then Alignment := taLeftJustify
    else Alignment := taRightJustify;
  end;

  function TCustomEdit.GetAsInteger:Integer;
  begin
    TryStrToInt(Text, result);
  end;

  procedure TCustomEdit.SetAsInteger(aVal: Integer);
  begin
     Text := IntToStr(aVal);
  end;

  function TCustomEdit.GetAsFloat:Extended;
  begin
    if Text = '' then result := 0
    else if not TryStrToFloat(Text, result) then
      Raise Exception.Create(rsInvalidNumbe);
  end;

  procedure TCustomEdit.SetAsFloat(aVal: Extended);
  begin
     Text := FloatToStr(aVal);
  end;

  function TCustomEdit.GetAsCurrency:Currency;
  begin
    if Text = '' then result := 0
    else if not TryStrToCurr(Text, result) then
      raise Exception.Create(rsInvalidNumbe);
  end;

  procedure TCustomEdit.SetAsCurrency(aVal: Currency);
  begin
     Text := CurrToStr(aVal);
  end;

VK_DECIMAL keypad dot by comma

When writing lazarus applications to non english locales there is a problem with the keypad "." (dot) when locale uses "," (comma) as decimal separator. I've been looking for a solution and couldn't find one here so after some research on internet and some experiments I endup setting with this:

Form.KeyPreview := True; Form.OnKeyDown := @FormKeyDown; Form.OnKeyPress := @FormKeyPress;

  { TFormBase }

  TFormBase = class(TForm)
    ...
  protected
    { protected declarations }
    fVK_Decimal : Boolean;
    ...
  end;

procedure TFormBase.FormKeyPress(Sender: TObject; var Key: char);
begin
   if fVK_Decimal and (key = '.') then key := DecimalSeparator;
end;

procedure TFormBase.FormKeyDown(Sender: TObject; var Key: word; Shift: TShiftState);
begin
  if (Shift = []) and (key = VK_DECIMAL) then
    fVK_Decimal := True; 
end;