How to customise the ComboBox PopupMenu

Hello everyone!

I’m currently working on a new UI for my plugins and I have a question about the customization of the ComboBox dropdown popup menu. I have created a custom lookandfeel for my plugin that rounds the corners of comboboxes.

I now want to achieve the same effect for the popup menu that comes up when you select an item. I got it to work for the menu items (as shown in the screenshot), however, there’s a white rectangle with a drop shadow that I cannot seem to get rid of (or customize).

In the screenshot, I have overwritten all methods I could find regarding the combobox including:

drawPopupMenuBackground, drawMenuBarBackground, drawPopupMenuItemWithOptions, drawMenuBarBackground, drawCallOutBoxBackground, drawTabButton, drawTabAreaBehindFrontButton and drawPopupMenuItem

yet, there’s still the rectangle visible.

(the little red rectangle sticking out ist just a leftover from experimenting with the methods, It is the box behind that I’m trying to edit)

Does anyone have an idea where I could find and customize this component that is being drawn?

I have also tried setting the PopupMenu::backgroundColourId of that ComboBox to another value with no effect.

Thanks for your help!
Best,
Thomas

Screenshot 2024-08-09 at 18.46.07

To disable the white background, you also need to set the PopupMenu::backgroundColourId to a transparent colour on the popup menu’s LookAndFeel.