#2 Administration graphical user interface to use and edit the karaoke playlist

[Julien Gouesse]

The karaoke playlist is the list of karaoke songs that are going to be played on multiple screens. The karaoke player is the element that plays each karaoke song in a window or a tab. The administrator must be able to edit the playlist in order to add, play and remove some karaoke songs. The administrator must be able to open multiple karaoke players to play one karaoke song at a time on multiple screens.

The a HTML anchor element with the attribute target at _blank and the attribute rel at opener must be used to open a new karaoke player in order to avoid using window.open() that doesn't work under Safari, to open it in a new window or tab and to set the field window.opener in the child window to the parent window containing the karaoke playlist.

The relationship previously set can be used to communicate between the parent window and the child windows. The former can use window.postMessage() to send some messages to the latter, the latter can use window.addEventListener("message", event => {}) to receive those messages and the latter can use event.source === window.opener to ensure that it treats only the messages coming from the former.

Actually, an administrator will probably use only one karaoke player and physically duplicate the screen display in order to avoid video software synchronization problems. In other words, LibreKaraoke will only see one screen for the administrator and another screen for the public even though a karaoke place can use multiple screens for the public.