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...get the first/last visible line of a TRichEdit?
Autor: Thomas Stutz
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Tip Rating (13):  
     


function RE_GetLastVisibleLine(RichEdit: TRichEdit): Integer;
const
  
EM_EXLINEFROMCHAR = WM_USER + 54;
var
  
r: TRect;
  i: Integer;
begin
  
{
   The EM_GETRECT message retrieves the formatting rectangle
   of an edit control.
  }
  
RichEdit.Perform(EM_GETRECT, 0, Longint(@r));
  r.Left := r.Left + 1;
  r.Top  := r.Bottom - 2;
  {
    The EM_CHARFROMPOS message retrieves information about the character
    closest to a specified point in the client area of an edit control
  }
  
i := RichEdit.Perform(EM_CHARFROMPOS, 0, Integer(@r.topleft));
  {
    The EM_EXLINEFROMCHAR message determines which
    line contains the specified character in a rich edit control
  }
  
Result := RichEdit.Perform(EM_EXLINEFROMCHAR, 0, i);
end;

{
  Sending the EM_GETFIRSTVISIBLELINE message to a multi-line edit control
  finds out which line is the first line visible.
  This is the line that is currently displayed at the top of the control.
}

function RE_GetFirstVisibleLine(RichEdit: TRichEdit): Integer;
begin
  
Result := RichEdit.Perform(EM_GETFIRSTVISIBLELINE, 0, 0);
end;

 

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