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How to scroll richedit smoothly?

ScrollBy function can only scrool the visible part of the richedit component,and richedit.perform(WM_VSCROLL,SB_LINEDOWN,0) can only scroll it by one line.
I want to scroll it smoothly,how to do it?
0
limin_chen
Asked:
limin_chen
1 Solution
 
mike_tippingCommented:
Place the richedit in a panel and increase the size of the richedit box to the full length of the RE document (either at design time or dinamically according to what is load into it). Only the section of the REB in the pannelo will be visible but if you increase and devrease the value of the rich edits top property the richedir box will slide up and down within the panel and give the impression of scrolling.

This may sound a bit of a cheat but it's the only way I could find to do it and it has worked fine so far.
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edeyCommented:
Another method would be to keep a full sized, hidden, rich edit, draw the thing to an off screen bmp and blt chunks of it to a scrollable control.  Note, this would work *muc* better with a read-only rich edit, in this case you wouldn't even have to keep the rich edit at all


Gl
Mike
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bryan7Commented:
listenning
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limin_chenAuthor Commented:
To edey:
  I like your method more.
  But if the richedit box is invisible or if it was created in program,the program here:
var
    back:tbitmap;
begin
  back:=tbitmap.create;
  back.canvas.width:=richedit.width;
  back.canvas.heigth:=richedit.height;
  bitblt(back.canvas.handle,0,0,back.canvas.width,back.canvas.height,getdc(richedit.handle),0,0,SRCCOPY);
  bitblt(mainform.canvas.handle,0,0,richedit.width,richedit.height,back.canvas.handle,0,0,SRCCOPY);
end;
  It could not get the correct image of the current richedit box,It is just filled with white color.I dont know the reason.
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limin_chenAuthor Commented:
Mike tipping:
  could you please tell me how to get the full lenght of the RE document displayed in RE box?
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mike_tippingCommented:
Increase The Height, the following code is probably not a brilliant as it could be but it works. Hide the Richedit box or Panel, and set

richedit1.height := Reditlength;

Then Show whichever you hid. If you don't do this you se the Reditlength function scanning the text.



Function TForm1.Reditlength;
Var
  nHeight, i, nSelStart : Integer;
Begin
  nSelStart := 1;
  {character to start scanning from}
  nHeight := 6;{this is the gap
                before the first text}
  For i:= 0 to Pred(Richedit1.Lines.Count) do
  begin
    Richedit1.SelStart := nSelStart;
    Richedit1.SelLength := 5;
    {scan 5 Characters in each line}
    nHeight := nHeight + RichEdit1.SelAttributes.Height + 3;
    {+3 for the gap between lines}
    nSelStart := nSelStart + Length(Richedit1.Lines.Strings[1]);
  end{for};
  REditLength := nHeight;
End;
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limin_chenAuthor Commented:
I found a better method to get the actul lines in pixel.Does it work right?

var
  h:integer;
begin
 richedit.peform    (wm_vscroll,sb_bottom,0);
 h:=getscrollpos(richedit.handle,sb_vert);
 inc(h,richedit.height);
{So ,I think the var h is the total lines in pixel}
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mike_tippingCommented:
It looks like this gives the position on the screen of the scroll bar toggle (thumb), not the length on the rich edit box

I presume your trying to scroll the richedit box with scroll bars switched off which would mean that getscrollpos returns 0 as there are no scroll 'thumbs' to get the position of.

I guess with ebey's solution your going to need to expand the rich edity box to it's full height as well, which gives us the same problem, how to get the length of the contents of the richedit box in pixels.
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duke_nCommented:
Var
Line:integer;
begin
Line:=20;//or something
SendMessage(RE.Handle, EM_LINESCROLL,0,MAKELONG(word(Line-(GetScrollPos(RE.Handle,SB_VERT)div 13)),0));//13-My Richedit's linesize
end;

this one works smoothly for me
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mike_tippingCommented:
so who gets the points?
0
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