Workshop: Pan and Zoom

Add panning and zooming to main panel in ButtonApp4

Panning

• Square should remembers its "real" position, as in previous code

• Somebody (Model) should remembers current X and Y panning offsets

  • Can hard code them for initial test

• Then apply the panning offsets as a correction factor whenever you:

  • draw()

  • pick, i.e. isInside()

• Provide user controls to change the panning offsets (in ControlGlobal)

• Choose range suitable for actual panel size ... preferably dynamically

• Could use direct mouse dragging to pan

• (Don't clobber "loc", make deep copy instead)

  • ie temp = new Rectangle(loc) not temp = loc

• Alternatives:

  • Could implement using Java2D transforms

  • Lay out the scroll bars on side and bottom of panel

  • Use a JScrollPane

Zooming

• Trickier: First, decide what does user mean by zoom? What is center point?

• Again, objects remember "real" position

• Again, apply zoom factor for draw() and isInside()

• Provide a user control for amount of zoom

Note

• When you download ButtonApp4, you won't get the GIF files for the arrows, so just change the ArrowButton code

  • From: setIcon (new ImageIcon ("leftArrow.gif"))

  • To: setText ("Left")

  • (and the same for rightArrow)