* add examples

examples/easyx/mystify.py

@@ -0,0 +1,106 @@
+# https://codebus.cn/zhaoh/post/screensaver-mystify
+# 该程序模仿的 Windows 经典屏幕保护程序“变幻线”，并使用了面向对象技术编写，初学面向对象时可以作为参考。
+#
+# 程序中，由多个连续的节点构成一个顶点对象，由四个顶点构成一个多边形对象，主程序有两个多边形在各自运动。更详细的，请参考源代码。
+import random
+from typing import List
+
+from easygraphics import *
+from dataclasses import dataclass
+
+WIDTH = 800
+HEIGHT = 600
+MAX_STEP = 9
+
+@dataclass
+class Point:
+    x:int
+    y:int
+
+class Vertex:
+    def __init__(self,count:int):
+        self.step_x = random.choice([-1,1])*random.randint(1,MAX_STEP)
+        self.step_y = random.choice([-1,1])*random.randint(1,MAX_STEP)
+        self.points = []
+        self.points.append(Point(random.randrange(WIDTH), random.randrange(HEIGHT)))
+        self._index = 0
+        for i in range(1,count):
+            p = self.points[i-1]
+            self.points.append(Point(p.x-self.step_x,p.y-self.step_y))
+
+    def get_head(self):
+        return self.points[self._index]
+
+    def get_next(self):
+        i = self._index+1
+        if i >= len(self.points):
+            i=0
+        return self.points[i]
+
+    def move(self):
+        p_head = self.get_head()
+        p_next = self.get_next()
+
+        p_next.x = p_head.x + self.step_x
+        p_next.y = p_head.y + self.step_y
+        self._index += 1
+        if self._index >= len(self.points):
+            self._index = 0
+
+        p = self.get_head()
+        if p.x < 0:
+            p.x = 0
+            self.step_x = random.randint(1,MAX_STEP)
+        elif p.x >= WIDTH:
+            p.x = WIDTH-1
+            self.step_x = -random.randint(1,MAX_STEP)
+        if p.y < 0:
+            p.y = 0
+            self.step_y = random.randint(1,MAX_STEP)
+        elif p.y >= HEIGHT:
+            p.y = HEIGHT-1
+            self.step_y = -random.randint(1,MAX_STEP)
+
+class Polygon:
+    def __init__(self,lines:int):
+        self.color = color_hsl(random.randrange(360),255,127)
+        self.vertex=[]
+        for i in range(4):
+            self.vertex.append(Vertex(lines))
+
+    def move(self):
+        # erase polygon tail
+        set_color(Color.BLACK)
+        move_to(self.vertex[3].get_next().x,self.vertex[3].get_next().y)
+        for i in range(4):
+            line_to(self.vertex[i].get_next().x,self.vertex[i].get_next().y)
+
+        # move every vertex
+        for i in range(4):
+            self.vertex[i].move()
+
+        # draw polygon head
+        set_color(self.color)
+        move_to(self.vertex[3].get_head().x,self.vertex[3].get_head().y)
+        for i in range(4):
+            line_to(self.vertex[i].get_head().x,self.vertex[i].get_head().y)
+
+        # 1% chance to change color
+        if random.randrange(100)==0:
+            self.color = color_hsl(random.randrange(360),255,127)
+
+def main():
+    init_graph(WIDTH,HEIGHT)
+    set_render_mode(RenderMode.RENDER_MANUAL)
+    set_background_color(Color.BLACK)
+    s1 = Polygon(7)
+    s2 = Polygon(12)
+
+    while is_run():
+        s1.move()
+        s2.move()
+        delay_fps(30)
+
+    close_graph()
+
+easy_run(main)