Stubbed ZoomChanged callback code and supporting class, demo.
Merge remote-tracking branch 'upstream/master' into zoomChanged
Found an easier way to set selection of cursor on mousedown.
  Doesn't seem to break any functionality.
Got rudimentary ZoomChanged callback with relevant boundaries.
Subscribed to XXXChanging events for testing. Comments in the code.
Clearer text on statusbar labels indicating what they'll show and how.
Merge branch 'master' into zoomChangedScaledView
Callback for ZoomChanged seems to be in all the right places and giving correct coords.
Cleaned up.
Fixed regression; wasn't checking for null callback.
Decided that usage of ZoomChanged would be improved by being called also when data is first visible.
Added extension method to return same data as ZoomChanged so user
  doesn't need to recreate view-querying code.
Merge pull request #7 from pckujawa/zoomChangedScaledView

ZoomChanged callback plus clarifications and refactoring