Reset causes flash of incorrect position in tutorial

[cdeil]

I was going through the platformer tutorial. It's really nice, thank you!

One small issue I noticed is that when using ESC to reset it works, but there's a fraction of a second where the player is in the lower left before it jumps to the center. This is with Python 3.13 on MacOS.

Is there a way to restructure the code to avoid this "flash of mispositioned content"?

To reproduce run this:

python -m arcade.examples.platform_tutorial.06_reset

Here's a screen screenshot showing the incorrect positioning:

Here's a recording:

Screen.Recording.2025-01-31.at.19.56.56.mov

[einarf]

Just calling setup() from the key input callback function is a bit brutal because all state changes should ideally always be done in on_update.

If we instead set a reset flag

        if key == arcade.key.ESCAPE:
            self.reset = True

.. and pick up the reset state in on_update

    def on_update(self, delta_time):
        if self.reset:
            self.setup()
            self.reset = False

What happens here is that you get the default camera position at 0, 0 because you re-create it completely so you get one frame with default camera.. then next frame with centered camera. The is usually on_update, on_draw, process input BUT this is never guaranteed. on_draw can happen more than once per cycle depending on os, environment and all window update settings.

An even better solution is to create a smarter and more light weight reset function but that would probably look very different based on what game you are creating?

[einarf]

This might also be somewhat related to pyglet/pyglet#1268 since events can be skipped BUT you can also configure a custom draw an update rate so the fact still stands that on_update is always where scene changes should be done.