Compatible plotyy and colorbar (or Confusion about Position, OuterPosition and ActivePositionProperty)

[David Bateman]

My colorbar/plotyy changes were recently added, and when implementing it 
I had some issues with the treatment of the position, outerposition and 
activepositionproperty properties of axes objects.

The behavior in matlab is described on the page

http://www.mathworks.com/access/helpdesk/help/techdoc/creating_plots/f1-32495.html

The actual size of the plot window is always determined by Position, 
whereas the space allocated for the plot window and text is always 
determined by OuterPosition. The ActivePositionProperty property is only 
used to determine how the difference between Position and OuterPosition 
are changed if the window is resized, so as gnuplot at the moment gives 
no means to feedback this information (or rather octave's interface to 
gnuplot), ActivePositionProperty is of no use.

Now how Octave treated these values before my change is that

* Octave's gnuplot interface uses OuterPosition in almost all cases to 
define the position as gnuplot's origin/size paradigm bests fits with 
use of OuterPosition. The exception is the plotyy function where 
currently ActivePositionProperty is abused to force gnuplot to have 
overlaying plots.

* The graphics.cc (void axes::properties::sync_positions (void)) 
function maintains a constant relationship between Position and 
OuterPosition. This is incorrect as adding a colorbar maintains the 
OuterPosition and adjusts position.

* The subplot function uses the OuterPosition property to recognize 
subplots that are to an existing axis.

So the correct implementation of the colorbar/plotyy function means that 
we'll have to fix this to be more Matlab like. Basically what this means 
is that

* Octave should base its decision on the window placement in the 
backends solely on the position property of the axis. This means that 
the intelligence for the axis size needs to be placed in Octave and not 
gnuplot.

* The synchronization code between the position and outerposition 
properties should be disabled till it is more intelligent and capable of 
handling colorbars. For now this means that space for the title, axis 
labels, legend, etc need to be hard coded into the default position of 
the axes.

I did that in the applied patch and fixed a couple of other issues and 
now have a fully working plotyy and colorbar command. In particular the 
mathworks example

surf(peaks(30))
colorbar('YTickLabel',{'Freezing','Cold','Cool','Neutral','Warm','Hot','Burning','Nuclear'})

works as expected when it didn't previously. However, the confusion 
about the Position, OuterPosition and ActivePositionProperty remains in 
the sense that the intelligence to calculate the size of the plot to 
allow for the axis labels, etc isn't in Octave and so its possible to 
make the plots label either fall outside the boundaries of the plot. At 
some point, we'll need to add this intelligence to Octave.

Regards
David

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