How do I determine the height of a line of text in a TMemo programmatically?

Question

I\'ve got a TMemo, and I want to always make it exactly high enough to display the number of lines it contains. Unfortunately, I don\'t quite know how to calculate that. I

Answer 1

You can write your own implementation of TCanvas.TextHeight for TMemo:

function CountMemoLineHeights(Memo: TMemo): Integer;
var
  DC: HDC;
  SaveFont: HFont;
  Size: TSize;
  I: Integer;

begin
  DC:= GetDC(Memo.Handle);
  SaveFont:= SelectObject(DC, Memo.Font.Handle);
  Size.cX := 0;
  Size.cY := 0;
//  I have not noticed difference in actual line heights for TMemo,
//    so the next line should work OK
  Windows.GetTextExtentPoint32(DC, 'W', 1, Size);
//  BTW next (commented) line returns Size.cY = 0 for empty line (Memo.Lines[I] = '') 
//    Windows.GetTextExtentPoint32(DC, Memo.Lines[I], Length(Memo.Lines[I]), Size);
  Result:= Memo.Lines.Count * Size.cY;
  SelectObject(DC, SaveFont);
  ReleaseDC(Memo.Handle, DC);
end;