# -*- coding: utf-8 -*-

# Copyright (C) 2003-2006 by Igor E. Novikov
# Copyright (C) 1997, 1998 by Bernhard Herzog 
#
# This library is covered by GNU Library General Public License.
# For more info see COPYRIGHTS file in sK1 root directory.

#
#	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)

