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# Copyright 2007-2008 Nanorex, Inc. See LICENSE file for details.
"""
DragBehavior.py - the DragBehavior API and some useful specific behaviors
@author: Bruce
@version: $Id$
@copyright: 2007-2008 Nanorex, Inc. See LICENSE file for details.
A DragBehavior
is a behavior in response to drag events
that a Drawable (called a "drag handle") can be given
(in addition to whatever highlighting and cursor behavior it has)
and that determines how drag events affect a position or position-determining state
(one which maps to a position, perhaps constrained to a line or plane, and/or a region, and/or quantized)
which this behavior is used to drag, and which usually (in part)
determines the drawn position of the drag handle.
"""
from exprs.instance_helpers import InstanceOrExpr
from exprs.attr_decl_macros import Arg, Instance
from exprs.__Symbols__ import Anything
from exprs.ExprsConstants import StateRef
from exprs.Highlightable import SavedCoordsys
class DragBehavior(InstanceOrExpr):
"""
abstract class
[#doc, maybe more defaults]
"""
# default implems
def on_press(self):
pass
def on_drag(self):
pass
def on_release(self):
pass
def on_release_in(self):
self.on_release()
return
def on_release_out(self):
self.on_release()
return
pass
# ==
class SimpleDragBehavior(DragBehavior): #works circa 070317; revised 070318
"""
the simplest kind of DragBehavior -- translate the passed state
just like the mouse moves (screen-parallel)
[#doc]
"""
##e rename to indicate what it does -- translate, 3d, screen-parallel
# (no limits, no grid, no constraint -- could add opts for those #e)
# note: for now, it probably doesn't matter if we are remade per drag event, or live through many of them --
# we store state during a drag (and left over afterwards) but reset it all when the next one starts --
# ASSUMING we actually get an on_press event for it -- we don't detect the error of not getting that!
# OTOH, even if we're newly made per drag, we don't detect or tolerate a missing initial on_press. ###BUG I guess
# args:
# a stateref to the translation state we should modify,
# and something to ask about the drag event (for now, highlightable, but later, a DragEvent object)
# (best arg order unclear; it may turn out that the DragEvent to ask is our delegate in the future -- so let it come first)
highlightable = Arg(Anything)
# for current_event_mousepoint (coordsys) -- will this always be needed? at least a DragEvent will be!
translation_ref = Arg(StateRef,
doc = "ref to translation state, e.g. call_Expr( LvalueFromObjAndAttr, some_obj, 'translation')" )
# state:
saved_coordsys = Instance( SavedCoordsys() ) # provides transient state for saving a fixed coordsys to use throughout a drag
def current_event_mousepoint(self, *args, **kws): #e zap this and inline it, for clarity? or move it into DragBehavior superclass??
return self.saved_coordsys.current_event_mousepoint(*args, **kws)
# note: the following methods are heavily modified from the ones in DraggableObject.
# [They are the methods of some interface, informal so far,
# but I don't know if it's exactly the one I've elsewhere called Draggable.]
def on_press(self):
self.saved_coordsys.copy_from( self.highlightable) # needed, since self.highlightable's coordsys changes during the drag!
point = self.current_event_mousepoint() # the touched point on the visible object (hitpoint)
self.oldpoint = self.startpoint = point
def on_drag(self):
# Note (for any on_drag method -- really about the interface it's in [###e refile]):
# we can assume this is a "real drag",
# not one which is too short to count (and is therefore treated as a click instead),
# since the caller is responsible for not calling on_drag until it decides this is a real drag.
oldpoint = self.oldpoint # was saved by prior on_drag or by on_press
point = self.current_event_mousepoint(plane = self.startpoint)
self.translation_ref.value = self.translation_ref.value + (point - oldpoint)
self.oldpoint = point
def on_release(self):
pass
pass # end of class SimpleDragBehavior
# end
|
