Delphi FMX Android FillText is Slow and Resource intensive

Question

I am drawing a (large) Boolean Table (Binary 0,1 values in a large grid pattern) with a PaintBox. As in the code below. Note: The code is simplified, only drawing random 0 and 1, to represent the problem. Also I have updated the question with the full code, since the commenter stated the initial question was vague.

Utilising the FillText to draw the (hundreds) of individual binary (0 or 1) values turned out to be SLOW!. Also when doing a lot of panning across the PaintBox, the app would freeze, and force close on the Android device.

So clearly the FillText is not sufficient for this case, and are wondering if anyone knows of a better technique?

procedure TMainWin.PaintBoxPaint(Sender: TObject; Canvas: TCanvas);
VAR Fcstroke:TStrokeBrush;
    xp,yp,Tsze:INTEGER;
    tw,th:SINGLE;
    p1,p2:TPointF;
    MyRect:TRectF;
begin
   Canvas.BeginScene;
   // Clear
   Canvas.Clear(TAlphaColorRec.Beige);
   Canvas.Fill.Color:= TAlphaColorRec.Black;
   Canvas.Fill.Kind:= TBrushKind.Solid;
   // Text Prop
   Canvas.Font.Family:= 'Roboto';
   Canvas.Font.Style:= [];
   Canvas.Font.Size:= 40;
   Canvas.Stroke.Thickness:= 2;
   Canvas.Stroke.Kind:= TBrushKind.Solid;
   Canvas.Stroke.DefaultColor:= TAlphaColorRec.Black;
   tw:= Canvas.TextWidth('0')*1.2;
   th:= Canvas.TextHeight('0');
   Fcstroke:= TStrokeBrush.Create(TBrushKind.Solid,TAlphaColorRec.Green);
   Fcstroke.DefaultColor:= TAlphaColorRec.Green;
   Fcstroke.Thickness:= 2;
   // Table
   Tsze:= 50;
   FOR yp:= 1 TO Tsze DO
   BEGIN
      // Horz table Line
      p1:= TPointF.Create(         tw,yp*th);
      p2:= TPointF.Create((Tsze+1)*tw,yp*th);
      Canvas.DrawLine(p1,p2,1,Fcstroke);
      // Vert table Line
      p1:= TPointF.Create(yp*tw,         th);
      p2:= TPointF.Create(yp*tw,(Tsze+1)*th);
      Canvas.DrawLine(p1,p2,1,Fcstroke);
      // Text
      FOR xp:= 1 TO Tsze DO
      BEGIN
         MyRect:= TRectF.Create(xp*tw,yp*th,xp*tw+tw,yp*th+th);
         IF (Random(10)>5) THEN
           Canvas.FillText(MyRect,'0',False,100,[],TTextAlign.Center,TTextAlign.Center)
         ELSE
           Canvas.FillText(MyRect,'1',False,100,[],TTextAlign.Center,TTextAlign.Center);
      END;
   END;
   // End
   Canvas.EndScene;
end;

Answer 1

You must encapsulate your your drawing by BeginScene and EndScene, or else the drawing will be very slow:

Canvas.BeginScene;
try
  //all your painting routines here
  Canvas.FillText(...);
  ... 
finally
  Canvas.EndScene;
end;