Rectangles

from fltk import *

class MyApp(Fl_Window):
    def __init__(self, x,y, w, h, label=None):
        Fl_Window.__init__(self, x, y, w, h, label)
        self.color(FL_BLACK)
        self.end()
        self.sqrsiz=100

    def handle(self, event):
        r=super().handle(event)
        if event==FL_RELEASE:
            x=Fl.event_x()
            y=Fl.event_y()
            if ((x//self.sqrsiz)+(y//self.sqrsiz))%2 == 1 :
                print('Black')
            else:
                print('White')

            return 1
        return r

    def draw(self):
        Fl_Window.draw(self)
        color=[FL_WHITE,FL_DARK3]
        #color=[7,0]
        for x in range(0,self.w(),self.sqrsiz):
            for y in range(0, self.h(), self.sqrsiz):
                c=color[(x+y)//100%2]
                fl_rectf(x,y,self.sqrsiz,self.sqrsiz,c)

height=500
app = MyApp(0,0, height, height)
app.show()
Fl.run()