As there doesn't seem to be an easy way to predict the maximized window's content size across platforms and renderers (you can get it with the window decoration included, but not easily without), the animation thread is blocked from starting until the window has actually maximized, and the correct content size has been established. This means that width and height have their correct values in setup().
If the user picks a renderer that doesn't support this, the sketch will start normally after a 2500ms delay, and they'll see an error message, naming their renderer as the culprit. The code for the JavaFX renderer is hacky; there just doesn't seem to be a better way.
Fixes #4181.