Changing the color of button changes the tint of the background image

This is the code for creating the upper right button:

    button = Button(size_hint_y=None, text='Einstellungen')
    # button.color = get_color_from_hex('#e0080d')

and the resulting app: (please ignore the crappy pixel art etc. 😉)

but when I uncomment the line to change the text color of the button, this is what it looks like:

[Dalker]

@inclement Thanks for taking the time to reply.

I now see that it does make sense that the order between the properties can matter in this situation. Well, not “properties” per se, but “canvas instructions”, as you point out, which I guess is the initial source of confusion: when looking at a .kv file for the first time, these really do “look” like if they were “properties” (and that’s why the newcomer can be confused by the “contamination” behaviour).

I’m not sure you’ve understood it fully

I definitely didn’t.

May I suggest adding a little paragraph around the end of the Pong tutorial (as an extra bullet to the Where to go now? section, where suggested extra features are mentioned, inviting the reader to try and modify/improve the game) explicitly mentioning something similar to:

• Make the ball yellow while keeping everything else white. Warning: anything under canvas: in a .kv file is not a class property, but rather a canvas instruction. This can have effects that seem unexpected to the newcomer. For instance, a Color: canvas instruction changes the color of the “brush” globally, and can thus affect other objects drawn by any subsequent canvas instructions of any object. It is therefore good practice to always specify a Color: explicitly at the beginning of the canvas: section of every class. In this suggested improvement to Pong, this is however not necessary: it is enough to surround the Ellipse: instruction of the ball’s canvas to change the brush to yellow right before drawing it, and then back to the default white right afterwards.

That way, the newcomer would immediately have the opportunity to be confronted to this behaviour and understand what to be aware of.

[CreamyCookie]

@inclement I can’t reopen this AFAIK.

It did work with your suggestion of using a Color instruction, but it doesn’t make any sense to me, why setting the color of a button changes the default color for other instructions. This certainly is neither user-friendly nor does it follow the Principle of least astonishment. Please expand on this.