This made me curious, and I checked by attaching a debugger to Messages.
The content view with the bubbles is a web view. All the other views (sidebar, input field, etc.) are native controls.
I guess this is a sort of "best of both worlds" approach. You have all the flexibility of HTML & CSS for complex content layout, and you get performance and usability of native sidebars and text fields.
The content view with the bubbles is a web view. All the other views (sidebar, input field, etc.) are native controls.
I guess this is a sort of "best of both worlds" approach. You have all the flexibility of HTML & CSS for complex content layout, and you get performance and usability of native sidebars and text fields.