CoeSwd6: User Def Axis Units: ScaledUnit-based axis units [1]
Bug Number: n/a
Release notes (y/n): no
For Release Nums: 7.1

Plot axes units are now based on Scaled Units (ScaledUnitPtr) rather 
than unit character string.  This means that, for example, a set of 
series slots with a mixture of FLOW units of cms, cfs, acre-ft/month 
and acre-feet/month are all mapped to the same vertical axes. (See the 
screenshot links below).

This development involved three fundamental changes:

  (a) Plot axes units are now based on Scaled Units rather than unit 
      character strings.
  (b) Slots are assigned to axes based on the slot's Unit Type rather 
      than their unit description (unit name) string.
  (c) Slot values are mapped to plot coordinates using the Scaled Units 
      associated with the axes to which Slot Curves are assigned, rather 
      than to the slot's current display units.

*Technical notes:

  (a) Change from unit character strings to ScaledUnitPtr in both 
      Sim/PlotInfo (class AxisInfo) and Q3GUI/SlotPlot (class SlotPlot::
      AxisItem).  See also related changes throughout the SlotPlot and 
      SlotCurve classes.
  (b) See method: bool SlotPlot::setAxes (SlotCurve* newSlotCurve).
  (c) See the updateCurveData() methods in each of the six SlotCurve 
      subclasses.

This still uses the same algorithm of establishing axes units in the 
process of dynamically adding slots to a plot -- EVEN FOR saved plots.
So, still, no persistent data exists for the units of any axis.

The following screenshots demonstrate adding two series slots to a plot 
-- one using CMS units, and the other using CFS.  Notice that, in 
RiverWare 7.0, the two slots are assigned to different vertical axes 
using unrelated scales.  In the new 7.1 development version, they are 
both assigned to the same axis, whose units are those of the FIRST SLOT 
added to the plot.

 http://cadswes2.colorado.edu/~philw/2017/CoeSwd6/2017-02-08/CmsCfsPlot-70.png
 http://cadswes2.colorado.edu/~philw/2017/CoeSwd6/2017-02-08/CmsCfsPlot-71a.png
 http://cadswes2.colorado.edu/~philw/2017/CoeSwd6/2017-02-08/CmsCfsPlot-71b.png

This is a coherent level of functionality, though it has some usability 
limitations.

Major subsequent development steps:

  (2) Preserving for each Axis: Unit Type and current Scaled Unit, and 
      adjusting the slot curve insertion algorithm to honor the axis Unit 
      Type assignments.

  (3) Support selection of a different Scaled Unit for non-time axes 
      (within the axis' Unit Type).

  (4) Support moving curves to the opposite axis (when the other axis is 
      either not yet used, or is of the same unit type).  Note that the 
      vertical scales of such axes will _not_ be synchronized (as it 
      currently true in RiverWare 7.0, see the screenshot above).

  (5) Adding an optionally shown visual indication in Legend Items of 
      which vertical axes a slot curve is associated with.

Note-1: My plan is to limit the support for (4) and (5) to vertical axis 
assignment, even though it could also apply to horizontal axis assignment.
The applicability of the latter would be very limited.

Note-2: An additional possible feature would be SWAPPING the vertical axes.
(That, actually, wouldn't be difficult to do also for the horizontal axes).

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