support external displays on controllers

[RJ Skerry-Ryan]

More hardware is equipped with external LCDs these days, for example the Maschine Mikro Mk2. Some folks have figured out how to write to the display over HID:
https://github.com/wrl/maschine.rs

We can already write to these via Javascript but the script author would need to write a rendering system in Javascript. An alternate option would be to allow a script to specify a skin XML file for an off-screen window / widget that we would then render to a pixmap when the window changes. By exposing the display pixmap to script, the script file could then deal with sending the pixmap to the device in a device-specific format.

[Be (be.ing)]

"An alternate option would be to allow a script to specify a skin XML file for an off-screen window / widget that we would then render to a pixmap when the window changes. By exposing the display pixmap to script, the script file could then deal with sending the pixmap to the device in a device-specific format."

It may be a good idea to implement this by making the JS able to define properties (like width and height) that change how Mixxx renders the pixmap rather than rendering it and then sending it to the JS engine to have the script manipulate it.

[Be (be.ing)]

FWIW, someone hacked Traktor's QML to manipulate what it sends to controllers with screens. Not sure if this has any info that would be helpful for making these controllers work with Mixxx:
https://github.com/ErikMinekus/traktor-kontrol-screens

[Be (be.ing)]

Changed the title of the bug to clarify that this is not about external monitors.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8695