Parameter Lists : porting to 0.13.4

[pijyoi]

Documenting some behavior changes to Parameter list types since 0.13.4.

1. Previously, it was possible to use values. Now limits must be used. (limits was added in 0.12.3)
2. Previously, it was possible to not specify value, the first value from limits would be used. Now if you don't specify it, the first value from limits will still be used but sigTreeStateChanged gets fired upon instantiation.

import pyqtgraph as pg
import pyqtgraph.parametertree as ptree

## If anything changes in the tree, print a message
def change(param, changes):
    print("tree changes:")
    for param, change, data in changes:
        print('  parameter: %s'% param.name())
        print('  change:    %s'% change)
        print('  data:      %s'% str(data))
        print('  ----------')
    
params = [
    # on 0.13.3, all four of the following work and callback doesn't fire

    # first two no longer work since 0.13.4
    # callback fires upon instantiation
    {'name': 'List A', 'type': 'list', 'values': [1,2,3]},
    {'name': 'List B', 'type': 'list', 'values': [1,2,3], 'value': 1},
    # third one works on 0.13.4 but callback fires upon instantiation
    {'name': 'List C', 'type': 'list', 'limits': [1,2,3]},
    # fourth one works and doesn't fire a callback upon instantiation
    {'name': 'List D', 'type': 'list', 'limits': [1,2,3], 'value': 1},
]

pg.mkQApp()
p = ptree.Parameter.create(name='params', type='group', children=params)
p.sigTreeStateChanged.connect(change)
t = ptree.ParameterTree()
t.setParameters(p, showTop=False)
t.show()

# don't need to run event loop
# pg.exec()