background color does not work for most components

[AlexanderGrathIBO]

Describe the bug
For some components (I can confirm label, image and container) the background color does not appear.

To Reproduce
Steps to reproduce the behavior:

1. create a LVGL project (8.x)
2. add a label to the screen
3. change background color
4. nothing happens, neither in the preview, nor when you click run, nor when I upload it to my device/screen

Expected behavior
For the background color to change.

Screenshots

Desktop (please complete the following information):

• OS: [macOS]
• Version [15.1.1]
• Apple M2

** LVGL version (if used)**

• 8.x

Additional context
It will change the code of screens.c, button works without problems and the code looks basically identical.
Potentially related issue: #644

[RamasyaR]

Change the opacity to 255 and you will see the background

[AlexanderGrathIBO]

Oh, that is an embarrassing oversight on my side, thanks for the fast response.

I would suggest setting that to 255 on default (when color is set).

[AlexanderGrathIBO]

So for anybody finding this with similar problems:
First check the opacity, some components have it set to 255 as the default value, some don't. You can set a new style, change it to the default value you want and than use that as the new default for the component.

The issue I had and why I opened this issue:
If you have a smaller screen make sure you can actually see all the UI elements. There is a button at the top right (within every sub-window) to enlarge it.
I thought I was going insane, sometimes things would work sometimes not, turns out I couldn't see all the settings and I was changing things in 'selected part'/'Ticks part' etc. and was wondering why none of the changes would do anything to the default behavior.

[mvladic]

We are using LVGL default values for the opacity. For example, Button widget has 255 opacity by default and Label widget has 0.

[mvladic]

I would suggest setting that to 255 on default (when color is set).

This makes sense. We can change opacity to 255 if it was 0 when color is changed.