Delphi Printer.Canvas.TextWidth property - delphi

Question

I'm trying to set the column width for printing with my Delphi application. Whatever I type for the string doesn't make the width fewer. Actually I don't understand why the property returns a string, it should return width in pixels.
My code is
Printer.Canvas.TextWidth('M');
Edit: i understood it doesn't return a string but what does 'M' mean? what i m trying to do is making a column narrower. my code is located at sudrap.org/paste/text/19688
Edit: i m afraid i couldn t explain the problem clearly, i m sorry. i want it to print like this:
not like this:

Answer 1

Try to check TextRect function. Using this function you can specify the target rectangle where the text should be printed, so you can narrow your column.
uses Graphics;
var
Text: string;
TargetRect: TRect;
begin
Printer.BeginDoc;
Text := 'This is a very long text';
// now I'll specify the rectangle where the text will be printed
// it respects the rectangle, so the text cannot exceed these coordinates
// with the following values you will get the column width set to 50 px
TargetRect := Rect(Margin, Y, Margin + 50, Y + LineHeight);
Printer.Canvas.Font.Size := 11;
Printer.Canvas.Font.Name := 'Arial';
Printer.Canvas.Font.Style := [fsBold];
Printer.Canvas.TextRect(TargetRect, Text);
Printer.EndDoc;
end;
Except this you can get with the TextRect function set of the formatting flags which can help you to specify e.g. text alignment, word wrap etc. For instance if you would like to center the text horizontally in the specified rectangle [100;100], [250;117] you can use the following.
Text := 'Centered text';
TargetRect := Rect(100, 100, 250, 117);
Printer.Canvas.TextRect(TargetRect, Text, [tfCenter]);
Or in your case might be more useful word wrap. Here's an example with rectangle [100;100], [200;134] where the text is automatically wrapped by the TextRect function.
Text := 'This is a very long text';
TargetRect := Rect(100, 100, 200, 134);
Printer.Canvas.TextRect(TargetRect, Text, [tfWordBreak]);

Answer 2

If you use a fixed width font on the canvas, you should get the same result for all single-character strings. If you use a variable width font, each character will return a different width.
Printer.Canvas.Font.Name = 'Courier New';
Printer.Canvas.Font.Size = 13;
ColumnWidth := Printer.Canvas.TextWidth('M');
For different fonts or different font sizes, you will get different results.

Answer 3

I don't see how you're saying it returns text. If it were returning text your code wouldn't even compile, you would be getting errors when you tried to multiply a number by text. You even convert it to a string for display purposes.
Are you being mislead by the fact that with a variable-width font that you'll get different answers for different strings? You can even get different answers for the same letters in a different order. For some fonts "WAM" will produce a different answer than "WMA" because of how the W and A fit together.
Also, you're simply assuming that your labels are narrower than 15 M's. While this is generally the case it's not good programming practice. Instead, you should be asking for the width of each label and using something a bit above the biggest answer.
Finally, your handling of LineHeight is atrocious. Simply add 300 to y if that's what you really want although it should be some multiple of your line height, not a fixed value. You'll get VERY different results from your code off printers with different DPI settings.
Have you even tried stepping through this code with the debugger to see what's going on internally? Your output of the position to the printout suggests you aren't using the debugger.