Re: Another small problem

Posted by Gregory on August 07, 2007

In Reply to Another small problem posted by Chris Nevin on August 04, 2007

: I have now run across the problem that using copying and pasting frequently in memo's causes a flicker on the text, does anyone know how to avoid this? I have seen ticker components (effectively what I am doing) that say they are 'flickerless' so I guess it must be a known problem with a solution?
: Thanks
: Chris

I did tests with following code and have no flicker with Delay at 100 milliseconds or higher. Just very little bit flicker when Delay is less then 50 to 60 msec.

procedure TForm1.Button1Click(Sender: TObject);
const
  Delay = 100; // smaller = faster, greater = slower
var
  S: string;
  i: integer;
  Start: DWORD;
begin
  S := Memo1.Text;
  Memo2.SetFocus;
  i := 0;
  while i < Length(S) do begin
    inc(i);
    if S[i] >= ' ' then begin // printable character
      Memo2.SelStart := Memo2.GetTextLen;
      Memo2.SelText := S[i];
    end
    else if S[i] = #13 then // carriage return
      Memo2.Lines.Add('');
    Start := GetTickCount;
    while GetTickCount < Start + Delay do
      Application.ProcessMessages;
  end;
end;

Completely flickerless is not possible by adding text to Delphi TMemo. You should output text direcly to Canvas and redraw only changed part of Canvas, more complicated ;)
Or draw directly using OpenGL or DirectX, still more complicated, or else obtain special component ;)

Follow Ups

Post a Followup

Name:
Password:

Subject:

Comments:
: : I have now run across the problem that using copying and pasting frequently in memo's causes a flicker on the text, does anyone know how to avoid this? I have seen ticker components (effectively what I am doing) that say they are 'flickerless' so I guess it must be a known problem with a solution? : : Thanks : : Chris : -------------------- : I did tests with following code and have no flicker with Delay at 100 milliseconds or higher. Just very little bit flicker when Delay is less then 50 to 60 msec. : procedure TForm1.Button1Click(Sender: TObject); : const : Delay = 100; // smaller = faster, greater = slower : var : S: string; : i: integer; : Start: DWORD; : begin : S := Memo1.Text; : Memo2.SetFocus; : i := 0; : while i < Length(S) do begin : inc(i); : if S[i] >= ' ' then begin // printable character : Memo2.SelStart := Memo2.GetTextLen; : Memo2.SelText := S[i]; : end : else if S[i] = #13 then // carriage return : Memo2.Lines.Add(''); : Start := GetTickCount; : while GetTickCount < Start + Delay do : Application.ProcessMessages; : end; : end; : Completely flickerless is not possible by adding text to Delphi TMemo. You should output text direcly to Canvas and redraw only changed part of Canvas, more complicated ;) : Or draw directly using OpenGL or DirectX, still more complicated, or else obtain special component ;)

DelphiLand Club members: enter your Membership password.
Guests can get a Forum Guest password by subscribing to the DelphiLand Newsletter.