TStringGrid cannot display very long (6K) strings

3
votes

I want to load some text in a TStringGrid. The strings are short except for a column where the string is over 100K. It seems that TStringGrid cannot handle this. The text does not appear in the cell until I double click the cell to edit it. But even then the behavior is erratic.

To reproduce: put a grid on the form, set goEdit= true. Run the application and double click a cell. Paste some text (should not contain enters) and press Enter to end the editing. The text disappear.

In the text I made, the limit is about 6208 ASCII chars.
Any quick fix/workaround for this?

2
delphidelphi-xe7
Why would you even want to show 6K long string in a single cell? To me that is just madnes. Your end user definitly won't be happy with the fact that he will have a verry long text which is wider than the screen shown in a single line. Why? Becouse he will bew forced to do lots of scrolling left and right in order to be able to read this text and he could quickly get lost and not know which part did he already read and which not. - SilverWarior
@SilverWarior - this is the format of the file I want to open and show to the user. Only on column is that big. And the user won't edit the 'big' text. Actually it is more like a viewer than an editor. But... anyway, I asked something, you answered something else :) - Beno
Display too long text shortened with ellipse . Make a custom event for editing/viewing the text in that cell somewhere outside of the grid, perhaps a popup window. - LU RD
What do you need to accomplish that requires displaying the whole 6k string in one cell? Some programs (for example, a database viewer program displaying a BLOB field) accomplish this by displaying a small subset of the string (or hex data) and then provide either a button or a contextual popup to get the original text in a specialized editor, copy it to clipboard, save it to disk, etc. Isn't that better than showing a huge string in a grid? - Leonardo Herrera
@Beno Even if you are making a viewer it is useless to try and show all that text in a single column becouse you can't show the entire text at the same time. So what I tried to point out was that you should probably find another more suitable way for showing your text. It would be much better if you go and show your long text in some other controll that has Word-warp functionality and can therefore show your text in multiple lines even thou it does not contain new line characters. it has to contain athleast spaces. - SilverWarior

2 Answers

9
votes

The text is painted with ExtTextOut. That is known to fail for very long strings. For instance: ExtTextOut fails with very long strings unless lower font quality specified. From what I can tell, it is tricky to work out exactly what length of string causes failure.

I suggest that if you need to support such long strings then you draw them yourself by implementing an OnDrawCell event handler. Don't draw the entire string, because after all the user won't be able to see anything outside the cell's rectangle. That way you will be able to avoid the problem of sending ExtTextOut a string that is too long for it to handle.

1
votes

you need to use Word break. of course without Word break nothing will be displayed. and of couse your text must contain spaces.

const
  N = 16000;
var
  R: TRect;
  s: String;
  i: Integer;
begin
  R := ClientRect;
  SetLength(s, N);
  for i := 1 to N do
    if Random(10) = 0 then
      s[i] := ' '
    else
      s[i] := Char(65 + Random(26));
  Canvas.Font.Color := clBlack;

  Canvas.TextRect(R, s, [tfCenter, tfVerticalCenter, tfWordBreak]);
end;