Very low framerate on osx at any window size above 320x240

[agdt3]

Hello,

I've attempted to implement the most basic example on a screen size above the given 320x240, and my framerate plunged significantly.

Code:

import sys, pygame

pygame.init()

size = width, height = 640, 480
speed = [2, 2]
black = 0, 0, 0

screen = pygame.display.set_mode(size)

ball = pygame.image.load("intro_ball.gif").convert()
ballrect = ball.get_rect()
clock = pygame.time.Clock()

while 1:
    clock.tick(60)
    pygame.display.set_caption("FPS: " + str(clock.get_fps()))
    for event in pygame.event.get():
        if event.type == pygame.QUIT: sys.exit()

    ballrect = ballrect.move(speed)
    if ballrect.left < 0 or ballrect.right > width:
        speed[0] = -speed[0]
    if ballrect.top < 0 or ballrect.bottom > height:
        speed[1] = -speed[1]

    screen.fill(black)
    screen.blit(ball, ballrect)
    pygame.display.flip()

Specs:
System: OSX Mojave 10.14.6
Python: 3.7.4 (installed from python bin, not brew, but path shows it to be using the )
Pygame: 1.9.6
SDL: 2.0.9_1 (installed via brew)

Framerates:
320x240 = ~60fps
640x480 = ~17fps
1024x768 = ~6.8fps

I've tried both clock.tick() and clock.tick(60).

Is there anything I'm obviously missing here? Thank you for your help!

Possibly related to #1032, but no solution was provided in that ticket either. I tried enabling SDL_HINT_RENDER_DRIVER=metal SDL_HINT_RENDER_VSYNC=1 as well, with no difference.

[agdt3]

After a bit of experimentation, it looks like changing the display settings to pygame.FULLSCREEN fixes this issue for some reason. Windowed mode remains slow.