I have a program displaying a few marks (short vertical lines) on screen. The whole drawing is in logical world using scaling transform. In most cases it works nicely. However I found sometimes the drawing is not expected, they marks (short lines) all disappered while everything else is drawn properly. After dig into the issue, I found a strange thing like this,
I draw the marks with method Graphics.DrawLine (pen, x1, y1, x2, y2). they are vertical lines, so x1 supposes to equal to x2. However, if x1 really equals to x2, the line will be invisilbe. If I just make x1 lightly off to x2, for example, x2 = x1 + 1, the line will be visible, but the line will be not exactly vertial as expected.
This problem will happen only occasionly when the Graphics object is scaled to some extent.