I'm using a multi-line
System.Windows.Forms.TextBox for a simple editor I'm working on. I didn't know how to get the cursor position, so I searched online and found (somewhere):
textbox.GetLineFromCharIndex ( textbox.SelectionStart )
for the line number and
textbox.SelectionStart - textbox.GetFirstCharIndexOfCurrentLine
for the position within the line. And they seemed to work properly until I noticed that I got some negative values for the position within the line when I selected some text.
A little experimentation and exploration resulted in abandoning the
GetFirstCharIndexOfCurrentLine* method in favor of the
GetFirstCharIndexFromLine method. So now I get the cursor position this way:
public static partial class LibExt
{
public static System.Drawing.Point
CurrentCharacterPosition
(
this System.Windows.Forms.TextBox TextBox
)
{
int s = TextBox.SelectionStart ;
int y = TextBox.GetLineFromCharIndex ( s ) ;
int x = s - TextBox.GetFirstCharIndexFromLine ( y ) ;
return ( new System.Drawing.Point ( x , y ) ) ;
}
}
* It appears that
GetFirstCharIndexOfCurrentLine uses the position of the caret to determine which line is "
current", whereas we're trying to use the
SelectionStart position.
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