While working at Canonical I worked on many different things such as reporting and resolving bugs, implementing drag and drop of tabs and creating a printing framework which works under confinement.
Drag and drop tabs
The component was initially written for the web-browser app, but then moved to the common ubuntu-ui-extras package.
Printing framework
This was made of many parts, as described below, to ensure that printing could be done under confinement.
A printing plugin to Qt (called qtubuntu-print) which generated PDF documents and sent via the use of content-hub.
The document would then be received by the ubuntu-printing-app which displays the print dialog, it also provides the notifications and queue dialog.
To configure printers, a panel was added to the ubuntu-system-settings app which allows for add, remove and editing of printer options.
The ubuntu-printing-app and ubuntu-system-settings both used a shared component for interacting with CUPS, this was stored in the ubuntu-ui-extras package.