Theme development

I'm making a subtheme and I need to replace a function of the parent theme (defined in .theme file) by my own. How can I do that?

for example if I want to replace
function theme_preprocess_html(&$variables)
by my own function?

thank you for your help

The banner on our (Drupal 8) town website is a photo image of autumn leaves.  I would like to be able to change the banner photo according to the season.  Could I use the Rotating Banner module to upload and sequence the photo images?  That is, can duration be set in days or weeks instead of minutes or hours?  If not via the Rotating Banner module, how else might a seasonal banner change be managed?

Hi.

I am very new to Drupal and Drupal's theme development.

I want to create my custom theme with my custom CSS framework so I don't want to select a base theme with already made classes.

I was reading about using Stark as it looks like a clean, base theme, but some says using it isn't a good idea as you can see here https://www.drupal.org/project/drupal/issues/2854576

Hi, I have a base theme in composer that I cannot edit. I want to remove a directory called "smartmenus" from the base theme using the libraries-override in my subtheme info.yml file.

My base theme is: drupal8_zymphonies_theme and its path is: themes/composer/drupal8_zymphonies_theme

My subtheme path is: themes/custom/lps

I want to remove: themes/composer/drupal8_zymphonies_theme/includes/smartmenus

My current info.yml has this:

I need to build a theme style with multiple tabs. But i found it anything theme similar with it.

Hi I can't insert class in child item of main menu and remove existing. Part of my code looks like this: