Firemonkey Grid Control - Aligning a column to the right

Question

I am using the FireMonkey Grid control but have an on-going issue in trying to right align a column. From other users postings, I have managed to create a new TColumn type, apply a style to this (text as HorzAlign=taTrailing) and in theory - thought that this would be solution. The values are provided by the OnGetValue function to the Grid control.

The problem is however that although at first it looks OK, if you scroll the bar/mouse wheel etc. the new TColumn type column does not appear to refresh correctly using the method/code below. It could be a bug/feature of the Grid (or the way I am doing it). I have tried .ReAlign etc...; but to no avail. The only way to get the grid back in line is do a column resize for example - which then redraws correctly?

The code below shows that it is a simple TGrid, with 2 cols, 1 the standard StringColumn and 1 my new StringColNum (wuth right alignment applied). - Any help appreciated as this one is a basic requirement of any grid work.

unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.Objects, FMX.Grid,
  FMX.Layouts, FMX.Edit;

type
  TForm1 = class(TForm)
    Grid1: TGrid;
    Button1: TButton;
    StyleBook1: TStyleBook;
    procedure Grid1GetValue(Sender: TObject; const Col, Row: Integer;
      var Value: Variant);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TStringColNum = class(TStringColumn)
  private
    function CreateCellControl: TStyledControl; override;
  public
    constructor Create(AOwner: TComponent); override;
  published
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}

constructor TStringColNum.Create(AOwner: TComponent);
begin
  inherited;
end;

function TStringColNum.CreateCellControl: TStyledControl;
var
  t:TEdit;
begin
  Result:=TStringColNum.Create(Self);
  Result.StyleLookup := 'textrightalign';
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Grid1.AddObject(TStringColumn.Create(Self));
  Grid1.AddObject(TStringColNum.Create(Self)); // Right Aligned column?

  Grid1.RowCount:=5000;
  Grid1.ShowScrollBars:=True;
end;

procedure TForm1.Grid1GetValue(Sender: TObject; const Col, Row: Integer;
  var Value: Variant);
var
  cell: TStyledControl;
  t: TText;
begin
  if Col=0 then
    Value:='Row '+IntToStr(Row);;

  if Col=1 then
    begin
      cell := Grid1.Columns[Col].CellControlByRow(Row);
      if Assigned(cell) then
        begin
          t := (Cell.FindStyleResource('text') as TText);
          if Assigned(t) then
            t.Text:='Row '+IntToStr(Row);
        end;
    end;
end;

end.

Kind regards. Ian.

Answer 1

All of which reminds me that I still haven't written my blog post about this.

Anyway, a grid cell can be any descendant of TStyledControl (basically any control). The default for a text cell is TTextCell, which is simply a TEdit. Being a TEdit means changing the alignment is really easy: just change the TextAlign property. No need to mess with styles (unless you really want to).

Your column needs to create your cells in the CreateCellControl method. You're actually creating an instance of your column which is your main problem.

You don't need the Create method for your column (it's doing nothing), so delete it (unless you need it for something else) and amend your CreateCellControl.

function TStringColNum.CreateCellControl: TStyledControl;
begin
  Result:=inherited;
  TTextCell(Result).TextAlign := taTrailing;
end;

Finally, your GetValue event handler needs do nothing more than return the value:

procedure TForm1.Grid1GetValue(Sender: TObject; const Col, Row: Integer;
  var Value: Variant);
begin
  if Col=0 then
    Value:='Row '+IntToStr(Row);

  if Col=1 then
    Value := 'Row '+IntToStr(Row);
end;

Answer 2

I think it is a laziness of Embarcadero.

adding/modifying 3 lines in FMX.Grid.pas solves this problem.

instead of modifiying original FMX.Grid pas, I recommend copying original FMX.Grid pas to your Project directory, including in your Project (add to Project) and adding/modifiying following lines.

TColumn = class(TStyledControl)
  private const
    HorzTextMargin = 2;
    VertTextMargin = 1;
  private
    FReadOnly: Boolean;
    FHorizontalAlign:TTextAlign;//Add this Line *********
    FEditMode: Integer;
    FApplyImmediately: boolean;
    ...
    ...
    procedure UpdateCell(ARow: Integer);
  published
    property HorizontalAlign: TTextAlign read FHorizontalAlign write FHorizontalAlign;//add this line *******
    property Align;
    property ClipChildren default False;

---

procedure TColumn.DefaultDrawCell(const Canvas: TCanvas; const Bounds: TRectF; const Row: Integer;
  const Value: TValue; const State: TGridDrawStates);
var
  R: TRectF;
  Layout: TTextLayout;
  LocalRow: Integer;
begin
  if FDrawable <> nil then
    FDrawable.DrawCell(Canvas, Bounds, Row, Value, State)
  else
...
...
      Layout.Opacity := AbsoluteOpacity;
      (*remark this line *****************
      Layout.HorizontalAlign := Grid.TextSettingsControl.ResultingTextSettings.HorzAlign;
      *)
      Layout.HorizontalAlign := HorizontalAlign;//add this line *****

finally you can set the new property in your Project. e.g:

MyColumn.HorizontalAlign:=TTextAlign.taCenter;