Move with a Scrolling Screen - Margins

Unlike the Move with a Scrolling Screen - Centered which centers the camera on the player, this example only moves the camera if the user gets within so many pixels of the edge. It allows for a ‘box’ in the middle where the user can move around and NOT move the camera.

Screen shot of using a scrolling window
sprite_move_scrolling_box.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
"""
Scroll around a large screen.

Artwork from https://kenney.nl

If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.sprite_move_scrolling
"""

import random
import arcade

SPRITE_SCALING = 0.5

DEFAULT_SCREEN_WIDTH = 800
DEFAULT_SCREEN_HEIGHT = 600
SCREEN_TITLE = "Sprite Move with Scrolling Screen Example"

# How many pixels to keep as a minimum margin between the character
# and the edge of the screen.
VIEWPORT_MARGIN = 200

# How fast the camera pans to the player. 1.0 is instant.
CAMERA_SPEED = 0.1

# How fast the character moves
PLAYER_MOVEMENT_SPEED = 7


class MyGame(arcade.Window):
    """ Main application class. """

    def __init__(self, width, height, title):
        """
        Initializer
        """
        super().__init__(width, height, title, resizable=True)

        # Sprite lists
        self.player_list = None
        self.wall_list = None

        # Set up the player
        self.player_sprite = None

        self.physics_engine = None

        # Used in scrolling
        self.view_bottom = 0
        self.view_left = 0

        self.camera_sprites = arcade.Camera(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT)
        self.camera_gui = arcade.Camera(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT)

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.player_list = arcade.SpriteList()
        self.wall_list = arcade.SpriteList()

        # Set up the player
        self.player_sprite = arcade.Sprite(":resources:images/animated_characters/female_person/femalePerson_idle.png",
                                           scale=0.4)
        self.player_sprite.center_x = 256
        self.player_sprite.center_y = 512
        self.player_list.append(self.player_sprite)

        # -- Set up several columns of walls
        for x in range(200, 1650, 210):
            for y in range(0, 1600, 64):
                # Randomly skip a box so the player can find a way through
                if random.randrange(5) > 0:
                    wall = arcade.Sprite(":resources:images/tiles/grassCenter.png", SPRITE_SCALING)
                    wall.center_x = x
                    wall.center_y = y
                    self.wall_list.append(wall)

        self.physics_engine = arcade.PhysicsEngineSimple(self.player_sprite, self.wall_list)

        # Set the background color
        arcade.set_background_color(arcade.color.AMAZON)

        # Set the viewport boundaries
        # These numbers set where we have 'scrolled' to.
        self.view_left = 0
        self.view_bottom = 0

    def on_draw(self):
        """
        Render the screen.
        """

        # This command has to happen before we start drawing
        arcade.start_render()

        # Select the camera we'll use to draw all our sprites
        self.camera_sprites.use()

        # Draw all the sprites.
        self.wall_list.draw()
        self.player_list.draw()

        # Select the (unscrolled) camera for our GUI
        self.camera_gui.use()

        # Draw the GUI
        arcade.draw_rectangle_filled(self.width // 2, 20, self.width, 40, arcade.color.ALMOND)
        text = f"Scroll value: ({self.camera_sprites.position[0]:5.1f}, {self.camera_sprites.position[1]:5.1f})"
        arcade.draw_text(text, 10, 10, arcade.color.BLACK_BEAN, 20)

        # Draw the box that we work to make sure the user stays inside of.
        # This is just for illustration purposes. You'd want to remove this
        # in your game.
        left_boundary = VIEWPORT_MARGIN
        right_boundary = self.width - VIEWPORT_MARGIN
        top_boundary = self.height - VIEWPORT_MARGIN
        bottom_boundary = VIEWPORT_MARGIN
        arcade.draw_lrtb_rectangle_outline(left_boundary, right_boundary, top_boundary, bottom_boundary,
                                           arcade.color.RED, 2)

    def on_key_press(self, key, modifiers):
        """Called whenever a key is pressed. """

        if key == arcade.key.UP:
            self.player_sprite.change_y = PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.DOWN:
            self.player_sprite.change_y = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.LEFT:
            self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.RIGHT:
            self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED

    def on_key_release(self, key, modifiers):
        """Called when the user releases a key. """

        if key == arcade.key.UP or key == arcade.key.DOWN:
            self.player_sprite.change_y = 0
        elif key == arcade.key.LEFT or key == arcade.key.RIGHT:
            self.player_sprite.change_x = 0

    def on_update(self, delta_time):
        """ Movement and game logic """

        # Call update on all sprites (The sprites don't do much in this
        # example though.)
        self.physics_engine.update()

        # Scroll the screen to the player
        self.scroll_to_player()

    def scroll_to_player(self):
        """
        Scroll the window to the player.
        This method will attempt to keep the player at least VIEWPORT_MARGIN
        pixels away from the edge.

        if CAMERA_SPEED is 1, the camera will immediately move to the desired position.
        Anything between 0 and 1 will have the camera move to the location with a smoother
        pan.
        """

        # --- Manage Scrolling ---

        # Scroll left
        left_boundary = self.view_left + VIEWPORT_MARGIN
        if self.player_sprite.left < left_boundary:
            self.view_left -= left_boundary - self.player_sprite.left

        # Scroll right
        right_boundary = self.view_left + self.width - VIEWPORT_MARGIN
        if self.player_sprite.right > right_boundary:
            self.view_left += self.player_sprite.right - right_boundary

        # Scroll up
        top_boundary = self.view_bottom + self.height - VIEWPORT_MARGIN
        if self.player_sprite.top > top_boundary:
            self.view_bottom += self.player_sprite.top - top_boundary

        # Scroll down
        bottom_boundary = self.view_bottom + VIEWPORT_MARGIN
        if self.player_sprite.bottom < bottom_boundary:
            self.view_bottom -= bottom_boundary - self.player_sprite.bottom

        # Scroll to the proper location
        position = self.view_left, self.view_bottom
        self.camera_sprites.move_to(position, CAMERA_SPEED)

    def on_resize(self, width, height):
        """
        Resize window
        Handle the user grabbing the edge and resizing the window.
        """
        self.camera_sprites.resize(int(width), int(height))
        self.camera_gui.resize(int(width), int(height))


def main():
    """ Main function """
    window = MyGame(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT, SCREEN_TITLE)
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()