CODEWITHSUNDEEP
delphidelphi-xe2
Koushik Halder
Koushik Halder

Reputation: 455

Delphi Form Flickering

I have an application created by Delphi XE2 having one form. When the application runs the form flicker to the Desktop it is no smooth. I have set "Double Buffer" and "Parent's Double Buffer" are true to the all possibilities. But the form ficler is present. Then I have added one FadeInTimer and it works fine. I question is "Without any Timer Delphi Form Flickering can be removed or not" . If possible please tell me how ?

Here is my code :

unit KoushikHalder01;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Buttons, Vcl.ExtCtrls,
  Vcl.ComCtrls;
type
  TForm01 = class(TForm)
    Label01: TLabel;
    Edit01: TEdit;
    Edit02: TEdit;
    BitBtn01: TBitBtn;
    BitBtn02: TBitBtn;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormShow(Sender: TObject);
    procedure FormHide(Sender: TObject);
    procedure BitBtn01MouseEnter(Sender: TObject);
    procedure BitBtn02MouseEnter(Sender: TObject);
    procedure BitBtn01MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure BitBtn02MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure BitBtn01MouseLeave(Sender: TObject);
    procedure BitBtn02MouseLeave(Sender: TObject);
    procedure BitBtn02Click(Sender: TObject);
    procedure BitBtn01Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form01: TForm01;

implementation

{$R *.dfm}

uses System.IOUtils;

procedure TForm01.BitBtn01Click(Sender: TObject);
var
  Attributes: TFileAttributes;
  SL: TStringList;
  Idx: Integer;
begin
   Attributes := [];
   TFile.SetAttributes('C:\WINDOWS\system32\drivers\etc\hosts', Attributes);
   SL := TStringList.Create;
   try
      SL.LoadFromFile('C:\WINDOWS\system32\drivers\etc\hosts');

     if
        SL.IndexOf('10.220.70.34    VIRTSDP25') <> -1
     then
        begin
        Edit02.Text := 'Your Host File Has Already Been Modified Successfully.';
        end;
     if
        SL.IndexOf('10.220.70.34    VIRTSDP25') = -1
     then
        begin
        SL.Add('10.220.70.34    VIRTSDP25');
        Edit02.Text := 'Your Host File Has Been Modified Successfully.';
        end;
     if
        SL.IndexOf('10.220.70.32    BSNLESDP25A') = -1
     then
        SL.Add('10.220.70.32    BSNLESDP25A');
     if
        SL.IndexOf('10.220.70.33    BSNLESDP25B') = -1
     then
        SL.Add('10.220.70.33    BSNLESDP25B');
     if
        SL.IndexOf('10.220.70.34    VIRTBSNLESDP25') = -1
     then
        SL.Add('10.220.70.34    VIRTBSNLESDP25');
     if
        SL.IndexOf('10.220.70.34    KOSDPTwentyfive.bsnl.in.net') = -1
     then
        SL.Add('10.220.70.34    KOSDPTwentyfive.bsnl.in.net');
     if
        SL.IndexOf('10.220.70.34    KOSDPTwentyfive.bsnl.net.in') = -1
     then
        begin
           SL.Add('10.220.70.34 KOSDPTwentyfive.bsnl.net.in');
           SL.SaveToFile('C:\WINDOWS\system32\drivers\etc\hosts');
        end;
     finally
       SL.Free;
   end;
    Include(Attributes, TFileAttribute.faSystem);
    Include(Attributes, TFileAttribute.faReadOnly);
    TFile.SetAttributes('C:\WINDOWS\system32\drivers\etc\hosts', Attributes);
end;

procedure TForm01.BitBtn01MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
   BitBtn01.Font.Color :=10379745;
end;

procedure TForm01.BitBtn01MouseEnter(Sender: TObject);
begin
   BitBtn01.Font.Color :=16711825;
end;

procedure TForm01.BitBtn01MouseLeave(Sender: TObject);
begin
   BitBtn01.Font.Color :=15756035;
end;

procedure TForm01.BitBtn02Click(Sender: TObject);
begin
  Form01.Close;
end;

procedure TForm01.BitBtn02MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
   BitBtn02.Font.Color :=10379745;
end;

procedure TForm01.BitBtn02MouseEnter(Sender: TObject);
begin
   BitBtn02.Font.Color :=16711825;
end;

procedure TForm01.BitBtn02MouseLeave(Sender: TObject);
begin
   BitBtn02.Font.Color :=15756035;
end;

procedure TForm01.FormClose(Sender: TObject; var Action: TCloseAction);
begin
   Doublebuffered := True;
end;

procedure TForm01.FormCreate(Sender: TObject);
begin
   Doublebuffered := True;
end;

procedure TForm01.FormHide(Sender: TObject);
begin
   Doublebuffered := True;
end;

procedure TForm01.FormShow(Sender: TObject);
begin
   Doublebuffered := True;
end;

end.

Upvotes: 2

Views: 5020

Answers (1)

quicoli
quicoli

Reputation: 622

DoubleBuffered doesn't always fix flicker, and in some situations can make things worse. You may consider only using DoubleBuffered during resizing, and then switch it back off when resizing is done. This property should only be used on those controls which are actually being resized. For example, when resizing the form, enable DoubleBuffered on the form. But when resizing just the contents of a panel, enable it just for that panel (and all its child controls).

But here are some tips from A Collection of Delphi Tips & Tricks (PDF)

Avoid flickering in graphics programming There are four ways to reduce flickering:

  1. Use the DoubleBuffered property of TWinControl descendants: set DoubleBuffered := true;

  2. If your control is not transparent, include csOpaque in ControlStyle: ControlStyle := ControlStyle + [csOpaque];

  3. Handle the WM_ERASEBKGND Windows message and set Msg.Result := 1;

  4. in the handler Use off-screen bitmaps (like double-buffering, but works for any control)

Upvotes: 2

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