Achille PACE

Delphi 11 - Windows 64 bits I am trying to draw various things in a TPaintBox using TDirect2D. I need to constantly update what's drawn inside. Unfortunately, my TPaintBox is flickering when I'm modifying it. I reproduced my problem in a small simpler project. .dfm: object FormMain: TFormMain Left = 0 Top = 0 Caption = 'FormMain' ClientHeight = 968 ClientWidth = 1470 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -12 Font.Name = 'Segoe UI' Font.Style = [] TextHeight = 15 object PaintBox: TPaintBox AlignWithMargins = True Left = 20 Top = 20 Width = 1389 Height = 928 Margins.Left = 20 Margins.Top = 20 Margins.Right = 20 Margins.Bottom = 20 Align = alLeft OnMouseMove = PaintBoxMouseMove OnPaint = PaintBoxPaint end end .pas: unit Main; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls; type TFormMain = class(TForm) PaintBox: TPaintBox; procedure PaintBoxMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer); procedure PaintBoxPaint(Sender: TObject); private { Déclarations privées } Index: Integer; public { Déclarations publiques } end; var FormMain: TFormMain; implementation uses Vcl.Direct2D, Winapi.D2D1; {$R *.dfm} procedure TFormMain.PaintBoxMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer); begin PaintBox.Invalidate(); end; procedure TFormMain.PaintBoxPaint(Sender: TObject); var LCanvas: TDirect2DCanvas; Poly: array of TPoint; begin LCanvas := TDirect2DCanvas.Create(PaintBox.Canvas, ClientRect); LCanvas.RenderTarget.SetAntialiasMode(D2D1_ANTIALIAS_MODE_PER_PRIMITIVE); LCanvas.BeginDraw; try { Drawing goes here } LCanvas.Pen.Color := clRed; LCanvas.Brush.Color := clNone; LCanvas.Pen.Width := 5; SetLength(Poly, 4); Poly[0] := Point(LCanvas.Pen.Width div 2 + Index, LCanvas.Pen.Width div 2 + Index); Poly[1] := Point(PaintBox.Width - LCanvas.Pen.Width, LCanvas.Pen.Width div 2); Poly[2] := Point(PaintBox.Width - LCanvas.Pen.Width, PaintBox.Height - LCanvas.Pen.Width); Poly[3] := Point(LCanvas.Pen.Width div 2, PaintBox.Height - LCanvas.Pen.Width); LCanvas.Polygon(Poly); inc(Index); LCanvas.MoveTo(10, 10); LCanvas.LineTo(PaintBox.Width - 10 - LCanvas.Pen.Width, PaintBox.Height - 10 - LCanvas.Pen.Width); finally LCanvas.EndDraw; LCanvas.Free; end; end; end. Putting the form's double buffered property to true stops the flickering. But if I put the TPaintBox inside a TPanel (whose double buffered property is also set to true), it starts flickering again, which makes me think there is another problem. I have also tried putting my TPaintBox in a frame, and adding that frame to my form (either by interface, or dynamically, and neither worked).

I used a TPaintBox because that's how mostly everything works in our 20 years old project. I'm a recent employee, but from what the senior dev told me, it was not possible to paint into a HWND and we had to paint into a TPaintBox's canvas. I have tried painting into a Panel's handle and it seems to work. Thanks !