import random
import tkinter

class RandomBall():
    '''
    定義球的類
    '''

    def __init__(self, canvas, scrnwidth, scrnheight):
        #canvas：畫布
        self.canvas = canvas
        #圓心座標
        self.xpos = random.randint(10, int(scrnwidth)-20)
        self.ypos = random.randint(10, int(scrnheight)-20)
        #球的速度，分速度為2個軸
        self.xvelocity = random.randint(2, 5)
        self.yvelocity = random.randint(2, 5)
        #半徑
        self.radius = random.randint(20, 120)
        #顏色RGB
        c = lambda: random.randint(0, 255)
        self.color = '#%02x%02x%02x'%(c(), c(), c())
        #螢幕長寬
        self.scrnwidth = scrnheight
        self.scrnheight = scrnheight

        #在畫布上畫球
    def create_ball(self):
        x1 = self.xpos - self.radius
        y1 = self.ypos + self.radius
        x2 = self.xpos + self.radius
        y2 = self.ypos - self.radius
        self.item = self.canvas.create_oval(x1, y1, x2, y2, fill=self.color, outline=self.color)

    #球的移動
    def move_ball(self):
        self.xpos += self.xvelocity
        self.ypos += self.yvelocity
        #球碰到螢幕邊緣彈回
        if self.xpos + self.radius >= self.scrnwidth\
                or self.xpos + self.radius <= 20:
            self.xvelocity = -self.xvelocity
        if self.ypos + self.radius >= self.scrnheight\
                or self.ypos + self.radius <= 20:
            self.yvelocity = -self.yvelocity
        #球的移動函式，就是移動複製
        self.canvas.move(self.item, self.xvelocity, self.yvelocity)

class ScreenSanver():
    '''
    定義屏保
    '''
    def __init__(self):
        #把N個球放在佇列中
        self.balls = []
        #球的數量
        self.num_balls = random.randint(6, 20)
        #生成框架
        self.root = tkinter.Tk()
        #取消邊框
        self.root.overrideredirect(1)
        #製作透明視窗
        self.root.attributes('-alpha', 0.3)
        #任何滑鼠移動都退出屏保
        self.root.bind('<Motion>', self.myquit)
        #任何鍵盤動作都可以退出屏保
        self.root.bind('<Key>', self.myquit)
        #得到螢幕大小規格
        w, h = self.root.winfo_screenwidth(), self.root.winfo_screenheight()
        #建立畫布
        self.canvas = tkinter.Canvas(self.root, width=w, height=h)
        self.canvas.pack()

        #畫布上畫球
        for i in range(self.num_balls):
            ball = RandomBall(self.canvas, scrnwidth=w, scrnheight=h)
            ball.create_ball()
            self.balls.append(ball)

        self.run_screen_saver()
        self.root.mainloop()

    #球的運動函式
    def run_screen_saver(self):
        for ball in self.balls:
             ball.move_ball()
        self.canvas.after(20, self.run_screen_saver)

    #解構函式
    def myquit(self, e):
        self.root.destroy()

if __name__ == "__main__":
    ScreenSanver()