NOTE: This patch aims to implement roughly what was in the 2.8 mockups: https://developer.blender.org/T57234#617574. However, as far as i know there's no proper design defined yet so it's outlined here.
# Design
Currently a viewport can be toggled into cameramode which shows either the scene's active camera or the viewport's local camera (when use_local_camera is enabled). This means it's not possible to directly view a camera without also activating it or setting it as the local camera first.
This can be improved by allowing to view any camera which is available in the viewport. A selector to choose which camera to show could replace the viewport name that is already displayed and make it interactive instead. This would make it something like a enum menu of what the viewport can display which could also present different view options like the viewpoints or persp/otho toggle.
{F8821246}
## Open questions
- When setting up a workspace one might want a viewport which always shows a certain camera. When accidentally leaving the cameraview the exact camera has to be chosen again. Maybe there could be a generic "lock viewport" option to solve this?
- When rendering from the cameraview it might be confusing that the active camera is used. Maybe it should be easily possible to render the camera that is currently viewed?
# Implementation
This patch allows the view3d.view_camera operator to switch to any camera by accepting a camera_id string. The operator won't affect the scene's active camera but rather store the camera local per viewport with the already existing view3d.camera property.
As the viewport then always uses a local camera the use_local_camera option becomes obsolete.
{F8817477}