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# Songwrite
# Copyright (C) 2001-2002 Jean-Baptiste LAMY
#
# This program is free software. See README or LICENSE for the license terms.
"""Cancel -- A framework for multiple undo/redo.
"""
NUMBER_OF_CANCEL = 20
class CancelmentStack:
def __init__(self, previous = None):
self.closures = []
self.previous = previous
def append(self, closure):
self.closures.append(closure)
add_cancel = add_redo = append
def prepend(self, closure):
self.closures.insert(0, closure)
def is_noop(self): return not self.closures
def __call__(self):
self.closures.reverse() # Operation must be undoed in the reverse order !!!
for closure in self.closures: closure()
class RootCancelmentStack(CancelmentStack):
def __init__(self):
self.closures = []
def append(self, closure):
self.closures.append(closure)
if len(self.closures) > NUMBER_OF_CANCEL: del self.closures[0]
def prepend(self, closure):
self.closures.insert(0, closure)
def pop_and_call(self):
if not self.closures: return 0
closure = self.closures.pop()
if isinstance(closure, CancelmentStack) and closure.is_noop(): return self.pop_and_call()
else:
closure()
return 1
class Context:
def __init__(self):
self.cancels = self.cur_cancels = RootCancelmentStack()
self.redos = self.cur_redos = RootCancelmentStack()
self.redoing = 0
def add_cancel(self, closure):
self.cur_cancels.append(closure)
#if (not self.redoing) and self.redos.closures:
# self.redos.closures *= 0
def add_post_cancel(self, closure):
self.cur_cancels.prepend(closure)
def add_redo(self, closure):
self.cur_redos.append(closure)
def add_post_redo(self, closure):
self.cur_redos.prepend(closure)
def get_last_cancelable(self):
if self.cancels.closures: return self.cancels.closures[-1]
return None
def cancel(self):
self.push_redo()
try: return self.cancels.pop_and_call()
finally: self.pop_redo()
def redo(self):
self.redoing = 1
self.push()
try: return self.redos.pop_and_call()
finally:
self.pop()
self.redoing = 0
def push(self):
new_stack = CancelmentStack(self.cur_cancels)
self.add_cancel(new_stack)
self.cur_cancels = new_stack
def pop(self):
if self.cur_cancels.is_noop():
try: self.cancels.closures.remove(self.cur_cancels)
except ValueError: pass
self.cur_cancels = self.cur_cancels.previous
def push_redo(self):
new_stack = CancelmentStack(self.cur_redos)
self.add_redo(new_stack)
self.cur_redos = new_stack
def pop_redo(self):
if self.cur_redos.is_noop():
try: self.redos.closures.remove(self.cur_redos)
except ValueError: pass
self.cur_redos = self.cur_redos.previous
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