Why does turtle open an even smaller screen when the canvas is small?

问题

I'm trying to draw on a small 200x200 screen using turtle, however the drawing doesn't pop up as full size, it opens a smaller window and I have to scroll up/down, left/right (just a bit) to see the whole drawing. I don't have this problem with larger windows. How do I prevent this?

import turtle
import random

height, width = 200, 200
screen = turtle.Screen()
screen.setup(width, height)
screen.setworldcoordinates(0, 0, width, height)

t = turtle.Turtle()
t.speed(1)

for _ in range(5):
    t.penup()
    t.goto(random.randint(20, width-20), random.randint(0, height-40))
    t.pendown()
    t.circle(20)

edit: screenshot, I want the actual size window instead of the scrolls

回答1:

Using small windows in turtle is a can of worms. If @TheOneMusic's simple solution (+1) is good enough for your purposes, go for it! On my system, your setworldcoordinates() call gets rid of the scroll bars, so I don't even see the issue. So, another approximate solution might be to upgrade to current Python and tkinter.

However, neither is an exact solution. If we add code to draw a 200 x 200 box around our drawing area:

t.penup()
t.color('red')
t.goto(0, 0)  # because of setworldcoordinates()
t.pendown()
for _ in range(4):
    t.forward(200)
    t.left(90)

We get the box skewed:

To solve this problem more precisely, involves uglier code:

from turtle import Screen, Turtle
from random import randint

TRUE_WIDTH, TRUE_HEIGHT = 200, 200

CURSOR_SIZE = 20  # for drawing frame around edge
RADIUS = 20
CHROME = 14  # magic number possibly derivable from tkinter

width, height = TRUE_WIDTH + CHROME, TRUE_HEIGHT + CHROME # needs to be slightly larger than 200 target

offset_x = CHROME / -2 + 2
offset_y = CHROME / 2 - 2

screen = Screen()
screen.setup(width, height)
screen.screensize(width/2, height/2)  # backing store needs to be smaller than window
screen.setworldcoordinates(0, 0, TRUE_WIDTH, TRUE_HEIGHT)

# Draw red frame around edge to "prove" drawing area
frame = Turtle(shape='square', visible=False)
frame.shapesize(TRUE_HEIGHT / CURSOR_SIZE, TRUE_WIDTH / CURSOR_SIZE)  # 200 x 200 frame
frame.color('red', 'white')
frame.penup()
frame.goto(TRUE_WIDTH/2 + offset_x, TRUE_HEIGHT/2 + offset_y)
frame.stamp()

turtle = Turtle()
turtle.speed('fastest')  # because I have no patience

for _ in range(5):
    turtle.penup()
    turtle.goto(randint(RADIUS, TRUE_WIDTH - RADIUS) + offset_x, randint(0, TRUE_HEIGHT - RADIUS*2) + offset_y)
    turtle.pendown()
    turtle.circle(RADIUS)

screen.exitonclick()

But this sort of detail work could easily be undone by a future release of turtle and/or tkinter. If you can live with turtle's default window, life gets easier.

回答2:

You could resize the window to 420×420.

If you don't want to resize your window, I suggest modifying the values for the keys "canvwidth" and "canvheight" keys in the turtle._CFG dictionary:

import turtle
import random

height, width = 200, 200
screen = turtle.Screen()
screen.setup(width, height)
screen.setworldcoordinates(0, 0, width, height)

turtle._CFG.update({"canvwidth": width-20, "canvheight": height-20}) # Removing the scroll bars

t = turtle.Turtle()
t.speed(1)


for _ in range(5):
    t.penup()
    t.goto(random.randint(20, width-20), random.randint(0, height-40))
    t.pendown()
    t.circle(20)

screen.exitonclick()

来源：https://stackoverflow.com/questions/62062749/why-does-turtle-open-an-even-smaller-screen-when-the-canvas-is-small

标签

python

turtle-graphics