# This program creates a single cell at the top left corner of a wxPython window, and
# flickers it. At every step, the value of 'cell_state', a scalar variable, is incremented. Then,
# depending on whether the value is odd or even, the color of the cell is determined, and
# a fresh cell is drawn with the new paint color.

# You may find this code useful when your CA has a 2D space, e.g., 'game of life'.
# Thus, at every time step the state of the 2D CA changes, and therefore you would have to
# paint a fresh 2D grid at each step.

# NOTE: As in '2Dcells.py', you have to write logic to populate 'cell_state' here. In this program,
# 'cell_state' is a simple scalar variable that holds a single number. For the game of life problem,
# 'cell_states' would have to be a matrix just like the one in '2Dcells.py'. In that program, you
# populate 'cell_states' only once since it represents the full space-time diagram, and paint it once.
# In the case of game of life, the 'cell_states' would represent a single state of the 2 dimensional CA.

# wxPython NOTE: Most of the code here is similar to '2Dcells.py' provided for the 1st problem.
# This program has two additional things: 'Timer' and 'PostEvent'. The flickering happens every half
# second, which is controlled by a 'Timer' whose event is bound to the 'Update' method. In that
# method, the cell is freshly painted. Once the painting is done, it explicitly generates a 'EVT_PAINT'
# event in order to invoke the 'OnPaint' method. In that method, a new timer is set that is stopped
# in the 'Update' method.

import wx

app = wx.App()
frame = wx.Frame(None, title="Draw on Panel", size = (640, 480))
panel = wx.Panel(frame)
panel.SetBackgroundColour("black")

def OnPaint(event):
    panel.dc = wx.PaintDC(panel)
    timer.Start(500)

def Update(event):
    if (frame.cell_state % 2 == 0): col = "red"
    else: col = "green"
    frame.cell_state += 1
    panel.dc.SetBrush(wx.Brush(col, wx.SOLID))
    panel.dc.DrawRectangle(0, 0, 50, 50)
    timer.Stop()
    wx.PostEvent(panel, wx.PaintEvent())

frame.cell_state = 0
panel.Bind(wx.EVT_PAINT, OnPaint)
timer = wx.Timer(panel)
panel.Bind(wx.EVT_TIMER, Update, timer)
        
frame.Center()
frame.Show(True)

# A mainloop is an endless cycle that catches up all events coming up to your application.
# It is an integral part of any windows GUI application.
app.MainLoop()