If a line is not selected it is aware of being grabbed at different positions along its length. At either end, in the middle or off middle (between the middle and the end). If it is grabbed at either of its ends the other end will stay where it is and the grabbed end will move to follow the mouse. If it is grabbed at its middle the whole line will move to follow the mouse. The lines length and its angle to the horizontal will not change. If the line is grabbed at any other point (off middle) then both ends of the line will remain anchored to their original positions and the line will behave like a rubber band (the line will break into two parts connected at the mouse)
If the line is selected, grabbing it at any point will cause the whole line to move to follow the mouse (exactly as if it had been grabbed in the middle).
| grabbing the line at its middle moves the whole line |
| grabbing the line at its end resizes the line and moves only the grabbed end |
| grabbing the line off center breaks the line in two and moves only the grabbed section of line (like a rubber band) |