How to reduce flicker from TImage on TForm

Question

I have a Delphi application with a couple of forms. For each form I used a TImage for a background, to give it a different look from the standard form look. The TImage is aligned to the client. The problem I have is that every time I click a button to open a new form, the form flickers. I do create the forms with the

frmSomeForm : TmfrSomeForm.create(self);
frmSomeForm.ShowModal;
frmSomeForm.Free;

I have tried to use the following code in the onCreate of the forms

DoubleBuffered := true;

but that does not seem to solve the problem, plus if I do use the dubbelbuffered then it makes my groupboxes that appear on my form to not be transparent. Can anyone please help.

I'm using Delphi XE2

How about you give up on TImage and paint the background in response to WM_ERASEBACKGROUND? As an aside why don't you use try finally? — David Heffernan, Feb 25 '14 at 19:32
I would typically use the Form's `OnPaint` event instead of intercepting the `WM_ERASEBKGND` message. — Remy Lebeau, Feb 25 '14 at 19:39
You can always try and set the ControlStyle = ControlStyle+ [csOpaque] at the Form's **OnPaint** procedure. — Filipe.Fonseca, Feb 25 '14 at 19:39
@DavidHeffernan I have no idea on how to do that, how to paint the background onto the form with a image in either jpg or png format — Japster, Feb 25 '14 at 19:40
@Remy That is still susceptible to flicker. Not sure why you wouldn't paint the background in WM_ERASEBACKGROUND. That's what it is for. — David Heffernan, Feb 25 '14 at 19:41
possible duplicate of [Tile/Center image in the forms background](http://stackoverflow.com/questions/15132326/tile-center-image-in-the-forms-background) — David Heffernan, Feb 25 '14 at 19:43
I would definitely advise you to avoid DoubleBuffered where possible and never to use it on a form. — David Heffernan, Feb 25 '14 at 19:46
@DavidHeffernan I did not even know you can paint an image on a form using the WM_ERASEBACKGROUND. I will start looking into this as the flicker with the TImage makes the application look bad — Japster, Feb 25 '14 at 19:47
Use the code from the near dupe I linked to. It is flicker free. — David Heffernan, Feb 25 '14 at 19:50
@DavidHeffernan Thanks David I will try this solution tomorrow morning, it is already late here in South Africa :-) — Japster, Feb 25 '14 at 19:58

Stijn Sanders · Accepted Answer · 2014-03-12T10:24:14.857

Catch the WM_ERASEBKG message and make it do nothing. Below code example should work. Windows fires a WM_ERASEBKG event to the window before WM_PAINT, and the default behaviour is 'clear' the form with clBtnFace (or clWindow depending on Windows version and/or theming). By causing WM_ERAGEBKG to do nothing (in advance of the WM_PAINT) the flicker should be avoided.

type
  TForm1 = class(TForm)
  private
    { Private declarations }
  protected
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd);
      message WM_ERASEBKGND;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

procedure TForm1.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
  Message.Result:=0;
end;

How to reduce flicker from TImage on TForm

1 Answers1