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""" Defines the base class for various types of zoom tools.
"""
from numpy import allclose, inf
# Enthought library imports
from traits.api import Enum, Float, HasTraits
class BaseZoomTool(HasTraits):
""" Defines traits and methods to actually perform the logic of zooming
onto a plot.
"""
# If the tool only applies to a particular axis, this attribute is used to
# determine which range to use.
axis = Enum("x", "y")
# The maximum ratio between the original data space bounds and the zoomed-in
# data space bounds. If None, then there is no limit (not advisable!).
max_zoom_in_factor = Float(1e5, allow_none=True)
# The maximum ratio between the zoomed-out data space bounds and the original
# bounds. If None, then there is no limit.
max_zoom_out_factor = Float(1e5, allow_none=True)
def _zoom_limit_reached(self, orig_position, orig_bounds, new_position, new_bounds):
""" Returns True if the new low and high exceed the maximum zoom
limits
"""
if orig_bounds == inf:
# There isn't really a good way to handle the case when the
# original bounds were infinite, since any finite zoom
# range will certainly exceed whatever zoom factor is set.
# In this case, we just allow unbounded levels of zoom.
return False
if allclose(orig_bounds, 0.0):
return True
if allclose(new_bounds, 0.0):
return True
if (new_bounds / orig_bounds) > self.max_zoom_out_factor or \
(orig_bounds / new_bounds) > self.max_zoom_in_factor:
return True
return False
#------------------------------------------------------------------------
# Utility methods for computing axes, coordinates, etc.
#------------------------------------------------------------------------
def _get_range_index(self):
""" Returns the index into the view_position and view_bounds
depending on value of self.axis.
"""
if self.axis == 'x':
return 0
else:
return 1
def _get_axis_coord(self, event, axis="x"):
""" Returns the coordinate of the event along the axis of interest
to the tool (or along the orthogonal axis, if axis="value").
"""
event_pos = (event.x, event.y)
if axis == "x":
return event_pos[ self._determine_axis() ]
else:
return event_pos[ 1 - self._determine_axis() ]
def _determine_axis(self):
""" Determines whether the index of the coordinate along the axis of
interest is the first or second element of an (x,y) coordinate tuple.
"""
if self.axis == "x":
return 0
else:
return 1
# EOF
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