Starting from the pictures models provided below, you will be able to suggest interfaces to your taste.
Original 1:

Original 2 (main screen et messages screen):

Original button 1:

Original button 2:

The added purple lines delimit vertical and horizontal areas that are not stretched.
Definition of the stretch.
Demonstration:
If (in addition to recolor the title bar) we draw two lines in areas stretch:

with new button :

we get:


The objects colors are not yet editable, it will remain fairly close in tone to the current theme.