CODEWITHSUNDEEP
delphitexttimervertical-scrollingtmemo
Rafik Bari
Rafik Bari

Reputation: 5037

Scrolling a Memo text using TTimer shows only the first 3 Lines

what i am trying to do right now is to create a scroling credit text using the TMemo component and TTimer 

 procedure TAboutBox.Timer1Timer(Sender: TObject);
 begin
 Memo1.ScrollBy(0,-1);
 end;

the Tmemo lines contain the text of the credit, something like :

Thankyou to :
Junifer lamda
Exemple user 2
Coder Monalisa
etc etc

Everything work as expected, i've set the timer.interval to 1ms , the text scroll smoothly but it displays only the 3 first lines then it displays a blank space, unless i click and drag manually using the mouse inside the memo, then it displays some lines then it disappears again when i release.

I tried with both TRichedit and TListBox but the problem persist. How could this be ?

Upvotes: 3

Views: 1654

Answers (1)

David Heffernan
David Heffernan

Reputation: 612993

It seems to me that ScrollBy is not designed to do what you desire. What's more I don't think that TMemo is necessary either.

I'd probably do this with a label and move it on the timer event. Like this:

procedure TScrollingTextForm.FormCreate(Sender: TObject);
begin
  Label1.Caption :=
    'Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do '+
    'eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad '+
    'minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip '+
    'ex ea commodo consequat. Duis aute irure dolor in reprehenderit in '+
    'voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur '+
    'sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt '+
    'mollit anim id est laborum.';
  Label1.Top := ClientHeight;
end;

procedure TScrollingTextForm.Timer1Timer(Sender: TObject);
begin
  Label1.Top := Label1.Top - 1;
end;

I found that I needed to make the form double buffered (DoubleBuffered := True) to avoid flicker when scrolling.

Upvotes: 4

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