在Pygame中沿光标方向绘制无限长度的线

我正在寻找有关 pygame 的帮助。我正在用 Python 开发简单的游戏来学习 Pygame。我想制作一个可以旋转并且可以用激光线射击的宇宙飞船。 我已经完成了方向键控制，我们也可以用鼠标位置旋转飞船，但是我在射击方面遇到了问题。我想从宇宙飞船位置到鼠标方向画一条无限长的线。我怎样才能做到这一点？这是我的代码：

  def draw_objects(self):
        SCREEN.fill(BLACK)
        self.target = pygame.mouse.get_pos()
        self.x = self.player.position[0] #player x position
        self.y = self.player.position[1] #player y position
        self.mx = self.target[0] #mouse x position
        self.my = self.target[1] #mouse y position
        self.slope=float(float(self.y-self.my)/float(self.x-self.mx+0.1)) #slope
        self.x_new =  DISPLAY_WIDTH #ray length
        self.y_new = self.y + self.slope * (self.x_new - self.x) 
        self.player.draw()
        self.draw_columns()
        for agent in self.all_agents:
            agent.draw()
            agent.draw_vectors()
        if self.player.shoot == True:
            pygame.draw.line(SCREEN, GREEN, self.player.position,(self.x_new, self.y_new), 2)

        pygame.display.update()

它无法正常工作，因为它只能在宇宙飞船的右侧工作。在其他情况下，它会绘制一条反射到光标的线。

我将感谢您的帮助。

slope不保持方向。
你必须得到以下标志player_x - mouse_x + 0.1并与使用x_new

    dx = player_x - mouse_x + 0.1

    reversed_sign_x = 1 if dx < 0 else -1

    x_new = reversed_sign_x * DISPLAY_WIDTH

完整的工作示例：

• 移动鼠标来移动线，
• 单击左按钮设置玩家新位置。

.

import pygame

# --- constants ---

BLACK = (0, 0, 0)
GREEN = (0, 255, 0)
DISPLAY_WIDTH = 800
DISPLAY_HEIGHT = 600

# --- functions ---

def calculate(player_x, player_y, mouse_x, mouse_y):
    dx = player_x - mouse_x + 0.1
    dy = player_y - mouse_y

    reversed_sign_x = 1 if dx < 0 else -1
    #reversed_sign_y = 1 if dy < 0 else -1

    slope = dy/dx

    x_new = reversed_sign_x * DISPLAY_WIDTH
    y_new = player_y + slope * (x_new - player_x)

    return x_new, y_new

# --- main ---

# - init -

pygame.init()
SCREEN = pygame.display.set_mode((DISPLAY_WIDTH, DISPLAY_HEIGHT))

# - objects -

player_x = DISPLAY_WIDTH // 2
player_y = DISPLAY_HEIGHT // 2

mouse_x = player_x
mouse_y = player_y

x_new, y_new = calculate(player_x, player_y, mouse_x, mouse_y)

# - mainloop -

clock = pygame.time.Clock()
running = True

while running:

    # - events -

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONDOWN:
            player_x, player_y = event.pos
        elif event.type == pygame.MOUSEMOTION:
            x_new, y_new = calculate(player_x, player_y, event.pos[0], event.pos[1])

    # - updates -

    # empty

    # - draws -

    SCREEN.fill(BLACK)
    pygame.draw.line(SCREEN, GREEN, (player_x, player_y), (x_new, y_new), 2)
    pygame.display.flip()

    # - FPS -

    clock.tick(25)

# - end -

pygame.quit()