Double Split Headerbar
After a number of experiments with adaptive solutions for the sidebar, I think the best thing to do short-term is to give up on the simple two-panel layout concept, and instead split the header bar a second time.
This has a number of advantages over other solutions:
- It's not very invasive in terms of changing the basic UI elements or workflow on the desktop
- It allows for a clean split into 3 separate views for mobile
- It doesn't require developing any new widgets
So at large widths we'd have 3 column with 2 header bar splits:
At smaller widths we'd show either sidebar + conversation list, or a message thread:
On mobile sizes we'd only show one view at a time:
On mobile, we'd use the conversation list view as the primary view (e.g. when the app opens), not the sidebar.