Second physical display

[riban-bw]

Is your feature request related to a problem? Please describe.
It may be advantageous to display engines, desktop, etc. on a physically attached display monitor. This would allow full user experience without requiring separate computer.

Describe the solution you'd like
Ability to display the second (Engines) display on a monitor plugged into one of the HDMI outlets.

Describe alternatives you've considered
Using VNC.

Additional context
I have not requested this before because of DIY builds that use the only HDMI output of a RPi3 but there may be a simple solution. Due to the extra overhead of a second display and associated engine GUIs running, it is not desirable to run second (VNC) screen unless required, e.g. for sound design. The configuration of this is in webconf. The configuration could allow enabling second display on second monitor. It would need to consider the current display configuration and hardware, e.g. if RPi3 and using HDMI for main output then only allow enable second display on VNC. Similarly if second display enabled on physical output, constrain selecting HDMI as a main display output (or automatically disable second display when selecting HDMI as main output on single HDMI devices).

Technically this could be achieved by choosing whether to run an extra X11 physical display with x11vnc connection or using tightvnc to display second screen. Configuration in webconf could offer various options in a list or have an extra checkbox:

• Enable second physical display
• Enable VNC

Logic would decide which displays to enable.

It would be advantageous to present these in admin page to allow full configuration from within the box, i.e. never needing external computer. This would work well if second physical display was enabled by default, i.e. could plug a monitor in on first boot and see second display. Then add a web browser that can be launched on the second display to access webconf.

Need to consider mouse and keyboard access. These may be advantageous on both displays so may need a method to switch between the two (rather than access both like a dual display desktop). Keyboard control of Zynthian may be desirable whilst also having keyboard input on the second display (desktop).

We currently call first display "UI" and second display "Engines" but maybe the second display could be called "Desktop" or similar.