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# Enthought library imports
from enable.api import BaseTool, KeySpec
from traits.api import Enum, Float, Instance
class SelectTool(BaseTool):
""" Base class for tools that handle some level of click-to-select
interaction. Handles the logic of different kinds of selection
modes. Subclasses only need to implement a few concrete methods
to handle actual selection/deselection.
"""
# The threshold, in pixels, around the cursor location to search for points.
threshold = Float(5.0)
# How selections are handled:
#
# "toggle"
# The user clicks on points (while optionally holding down a modifier
# key) to select or deselect them. If the point is already selected,
# clicking it again deselects it. The modifier key to use is set by
# **multiselect_modifier**. The only way to deselect points is by
# clicking on them; clicking on a screen space outside of the plot does
# not deselect points.
# "multi"
# Like **toggle** mode, except that the user can deselect all points
# at once by clicking on the plot area away from a point.
# "single"
# The user can only select a single point at a time.
# "off"
# The user cannot select points via clicking.
selection_mode = Enum("toggle", "multi", "single", "off")
# The modifier key to use to multi-select points. Only used in **toggle**
# and **multi** selection modes.
multiselect_modifier = Instance(KeySpec, args=(None, "control"), allow_none=True)
def _get_selection_state(self, event):
""" Returns a tuple reflecting the current selection state
Parameters
----------
event : enable KeyEvent or MouseEvent
Returns
-------
(already_selected, clicked) : tuple of Bool
clicked is True if the item corresponding to the input event has
just been clicked.
already_selected indicates that the item corresponding to the
input event is already selected.
"""
raise NotImplementedError
def _get_selection_token(self, event):
""" Returns a token corresponding to the selection event. This token
is passed in to the select and deselect methods. By default, this
just returns the event itself.
"""
return event
def _select(self, token, append=True):
""" Selects the given token.
"""
raise NotImplementedError
def _deselect(self, token, append=True):
""" Deselects the given token.
"""
raise NotImplementedError
def normal_left_down(self, event):
""" Handles the left mouse button being pressed when the tool is in the
'normal' state.
If selecting is enabled and the cursor is within **threshold** of a
data point, the method calls the subclass's _select" or _deselect
methods to perform the appropriate action, given the current
selection_mode.
"""
if self.selection_mode != "off":
already_selected, clicked = self._get_selection_state(event)
modifier_down = self.multiselect_modifier.match(event)
token = self._get_selection_token(event)
if (self.selection_mode == "single") or\
(self.selection_mode == "multi" and not modifier_down):
if clicked and not already_selected:
if self.selection_mode == "single" or not modifier_down:
self._select(token, append=False)
else:
self._select(token, append=True)
event.handled = True
else:
self._deselect(token)
else: # multi or toggle, and modifier_down is true
if clicked:
if already_selected:
self._deselect(token)
else:
self._select(token)
event.handled = True
return
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