# Sketch - A Python-based interactive drawing program
# Copyright (C) 1997, 1998 by Bernhard Herzog
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Library General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Library General Public License for more details.
#
# You should have received a copy of the GNU Library General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# Classes:
#
# WidgetWithModes
#
# A mix-in class for widgets with several input modes.
# Modes may be temporary or permanent.
#
# Temporary modes are usually only active until the user
# has pressed and released a mouse button. The zoom
# command in the SketchCanvas class is implemented as a
# temporary mode for example. When a temporary mode is
# deactivated (probably because the user released the
# mouse button or pressed ESC) the mode that was active
# before is activated again.
#
# The permanent modes are called `major modes' here and
# require an explicit command from the user to switch to
# another major mode. Examples are the selection mode and
# the edit mode the SketchCanvas.
#
# Temporary mode can even be nested: A user might select
# the `Update From...' button in the FillStyle dialog
# which activates the pick_object mode in the canvas
# widget. While this mode is active, indicated by a
# different cursor shape, she might also select the zoom
# button in the tool bar to make the area where the object
# she wants to pick is a little larger. When the zoom
# command is complete the pick_object mode is
# automatically activated again and the user can click on
# the object whose fill style should be copied into the
# fill style dialog.
#
#
# Mode
# MajorMode(Mode)
# TemporaryMode(Mode)
#
# These represent the modes of the widget. Each instance
# basically provides callable objects (methods usually)
# that are invoked when certain events occur.
#
#
def noop(*args, **kwargs):
pass
class Mode:
isMajorMode = 0
isTemporaryMode = 0
def __init__(self, enter, button_down, mouse_move, button_up,
exit = noop, cancel = noop, **rest):
self.enter = enter
self.button_down = button_down
self.mouse_move = mouse_move
self.button_up = button_up
self.exit = exit
self.cancel = cancel
for key, value in rest.items():
setattr(self, key, value)
class MajorMode(Mode):
isMajorMode = 1
class TemporaryMode(Mode):
isTemporaryMode = 1
class SketchModeError(Exception):
pass
class WidgetWithModes:
def __init__(self):
self.mode_stack = ()
self.mode = MajorMode(noop, noop, noop, noop, noop)
def push_mode(self, mode):
self.mode_stack = (self.mode, self.mode_stack)
self.mode = mode
def pop_mode(self):
try:
self.mode, self.mode_stack = self.mode_stack
except ValueError:
raise SketchModeError('mode stack empty')
def exit_temporary_mode(self, cancel = 0):
if self.mode.isTemporaryMode:
if cancel:
self.mode.cancel()
self.pop_mode()
def cancel_temporary_mode(self):
self.exit_temporary_mode(1)
def enter_mode(self, mode, *args):
if mode.isMajorMode:
# cancel all currently active temporary modes
while self.mode.isTemporaryMode:
self.cancel_temporary_mode()
if not self.mode.isMajorMode or self.mode_stack != ():
raise SketchModeError('mode stack corrupted')
self.mode.exit()
self.mode = mode
apply(self.mode.enter, args)
else:
self.push_mode(mode)
apply(self.mode.enter, args)
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