The SynEdit control has an event OnGutterGetText. I would like to use this to make the gutter only display every 10th line number (also line 1 and currently selected line). The same way that the Delphi (XE7) IDE works. How do I determine whether to show the line or not using this event?
The question transpires to be nothing to do with the edit control in reality. You simply want to know if a is an exact multiple of b. That is so if the remainder of a divided by b is zero. And the remainder operator in Delphi is mod.
if a mod b = 0 then
Now, in your case you want
if LineNum mod 10 = 0 then
This assumes that LineNum is one based. If it is zero based then you need
if (LineNum + 1) mod 10 = 0 then