All,
I have been looking at some of the recent z-order changes and have found an
issue that breaks previous behavior. Previously when
items were added to a Figure or an Axes with the same z-order value, they were
rendered in order of when they were added, so that
the first one added is 'underneath' the others and the last one added is
rendered 'over' all the other items of the same z-order
value. This no longer is the case. The following snippet of code demonstrates
the problem:
#===============================================================
class ZSortClass( object ):
def __init__( self, name, zorder = 0 ):
self.name = name
self.zorder = zorder
def doit( self ):
print "z-order [%s] = %s" % (self.name, self.zorder)
# Instantiate out of order to prove a point
a = ZSortClass( 'a', 0 )
c = ZSortClass( 'c', 0 )
b = ZSortClass( 'b', 0 )
all = [ a, b, c ]
dsu = [ (x.zorder, x.doit, x.name) for x in all ]
print dsu
dsu.sort()
print dsu
#===============================================================
All three instances have the same 'zorder' value, which causes the sort command
to resort to sorting on the memory address. This
can change from run to run. In simple cases the memory addresses typically
increase in order of instantiation, but in larger blocks
of code, python can perform garbage collection at any time and this would no
longer hold true, and cause the effect to appear random
(This is also affecting the rendering of filled continents in basemap). I
couldn't think of an easy solution without making some
intrusive changes to what is already in place, so I thought that I'd post my
findings for further discussion.
--James Evans
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