downthemall | WebExtension | Browser Plugin library

I'm customizing my awesome-wm taskbar and what I'm trying to achieve is :

• have a tasklist with fixed items width, which can shrink if there is not enough space
• have a button right after the tasklist to open a program launcher on click (rofi), this button should never shrink

For debugging purpose, the button was replace by the red textbox

This is how it looks when there is only few items, exactly what I want :

When there is a lot of clients, the tasklist items shrink as expected, but the textfield too :

here is my complete rc.lua, which is mainly the same as the default one :