Phosh is graphical shell for mobile, touch based devices like smart phones. It’s the default graphical shell on Purism’s Librem 5.
Here is an overview over phosh.
Phosh's source code can be found here.
From this article of early experiences with conversion:
Once in convergence mode you can drag applications over to the larger screen with a mouse, however there are also already a number of useful key bindings using the “Super” key (the key between the left Fn and Alt keys) that make convergence mode very keyboard friendly:
Super + (Left|Right): Tile the focused window to the left or right side of the active screen Super + Shift + (Left|Right): Move the focused window to the left or right display Super + (Up|Down): Maximize or unmaximize the focused window Super + a: Open the App Launcher, where you can type in the name of the application to launch, or select it with arrow keys Super + s: Open the App Switcher (similar to hitting the bottom section of the touchscreen on the phone). This allows you to switch between running applications using the arrow keys