Gnuplot canvas terminal

### Mouse interaction with gnuplot canvas

Mouse movement
  Track mouse coordinates
Left-click
  Mark current coordinates on plot

| Toggle grid lines (if present)
| Unzoom (restores original plot)
| Rezoom
1 | Display/Hide plot #1

Zooming
  Firefox - Click and drag with right mouse button
  Opera - Mouse buttons are problematic. To zoom you must set the middle-button mode to "Gestures". Click and release the middle button once to select one corner of the zoom box; then click a second time in the same place and drag to define the other corner.
  Safari - Untested
  IE - Untested