External display as secondary monitor
@eloli
Submitted by Eugenia Loli-Queru
Description
Feature request: Please add an icon in the preview toolbar that looks like a monitor. When you click that icon, the video preview will now be rendered in a secondary X display -- if one is available -- full screen. Right clicking on that secondary full screen playback display and there should be a small menu to ask me if I want the playback to be 1:1 size, or resized to fill the screen. If for example I have a 1366x768 secondary screen, my project settings are set to 1280x720 (no matter the source resolution), and I choose to display as 1:1, then the video should playback as 1280x720, centered in the monitor, with black borders around it. If I choose to resize it, then just take over that screen.
If it's too difficult programmatically to add the right-click menu on the playback screen itself, add it as a drop-down menu (the ones with the arrow) next to the monitor icon in the main preview toolbar.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=603205