# animation.py
# Walker M. White (wmw2)
# November 8, 2012
"""Module to show off a touch application.

Touch events are broken into three broad categories:

    on_touch_down: use recently pressed the mouse/finger

    on_touch_up: user released mouse/finger
    
    on_touch_move: used moved mouse/finger while holds it down.
    
All three of these are a necessary part of a touch application."""
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.graphics.vertex_instructions import Line, Rectangle, Ellipse
from kivy.graphics.context_instructions import Color
from kivy.properties import ObjectProperty
from kivy.factory import Factory
from kivy.config import Config
from kivy.app import App

# RGB Colors for our various drawings
LINE_COLOR = Color(1,0,0)
SPOT_COLOR = Color(0,0,1)

SPOT_RADIUS = 20

class TouchPanel(FloatLayout):
    """Drawing canvas to display the shape."""
    # Necessary fields to represent state

    # Coordinates of last touch event
    # Invariant: 2-element tuple of float or None.  If None, either _state
    # is 'spots' or the mouse/finger is not down.
    _anchor = None
    
    # Current shape to draw
    # Invariant: Either 'line' or 'spots'
    _state = 'line'
    
    def drawLine(self,x0,y0,x1,y1,color):
        """Draw a line from (x0,y0) to (x1,y1) of the given color.
        
        Precondition: x0, y0, x1, y1 are all floats.  color is a
        Kivy color object."""
        self.canvas.add(color)
        self.canvas.add(Line(points=[x0,y0,x1,y1],width=2))

    def drawSpot(self,x,y,color):
        """Draw a circle of radius SPOT_RADIUS centered at (x,y) with the given color.
        
        Precondition: x, y are both floats.  color is a Kivy color object."""
        self.canvas.add(color)
        self.canvas.add(Ellipse(pos=(x-SPOT_RADIUS/2.0,y-SPOT_RADIUS/2.0),size=(SPOT_RADIUS,SPOT_RADIUS)))

    def setState(self,state):
        """Change the state of this drawing panel to state.
        
        Changing the state automatically sets the _anchor to None.
        
        Precondition: state is one of 'line' or 'spots' """
        assert state == 'line' or state == 'spots', `state`+' is an invalid state'
        self._state = state
        self._anchor = None
        
        # Work around for weird bug I do not understand.
        self.canvas.ask_update()

    def on_touch_down(self,touch):
        """Called when the user presses the mouse or a finger (on touch screens)
        
        Precondition: touch is a Kivy MotionEvent object"""
        print 'Touch down at point '+str((touch.x,touch.y))

        # Only need to track previous touches if drawing lines.
        if self._state == 'line':
            self._anchor = (touch.x,touch.y)
        elif self._state == 'spots':
            # Spots can be drawn immediately
            self.drawSpot(touch.x,touch.y,SPOT_COLOR)
        
    def on_touch_up(self,touch):
        """Called when the user releases the mouse or a finger (on touch screens)
        
        Precondition: touch is a Kivy MotionEvent object"""
        print 'Touch up at point '+str((touch.x,touch.y))

        # Only need to track previous touches if drawing lines.
        if self._state == 'line':
            self._anchor = None
 
    def on_touch_move(self,touch):
        """Called when the user moves the mouse or a finger (on touch screens)

        Precondition: touch is a Kivy MotionEvent object"""
        print 'Touch move to point '+str((touch.x,touch.y))
        
        # Only need to track previous touches if drawing lines.        
        if self._state == 'line' and not self._anchor is None:
            self.drawLine(self._anchor[0],self._anchor[1],touch.x,touch.y,LINE_COLOR)
            self._anchor = (touch.x,touch.y)
        elif self._state == 'spots':
            # Just draw a spot in place
            self.drawSpot(touch.x,touch.y,SPOT_COLOR)


class TouchMain(BoxLayout):
    """Main panel with buttons.
    
    Defined entirely in the touch.kv file."""
    # Kivy property for coordination with .kv file.
    panel = ObjectProperty(None)


class TouchApp(App):
    """Instance is an application that draws according to touch."""
    
    def build(self):
        """Build application with a single internal panel"""
        """Build application with a single internal panel"""
        Config.set('graphics', 'width', '400')
        Config.set('graphics', 'height', '400')
        return TouchMain(size=(400,400))

# Register UI elements for .kv files.
Factory.register("TouchPanel", TouchPanel)

# Application Code
if __name__ == '__main__':
    TouchApp().run()