As some may have noticed I have lately patched “Primary Display” support into a few of our components. It all started with the display settings dialog… But let me start right at the beginning.
“Primary” is a setting of X11’s RandR extension that “is expected to be used by desktop environments to mark the screen that should hold the primary menu bar or panel” (quoted from the specification). So in short: the “Primary Display” should hold your panels, your desktop icons, your notifications, potentially your presenter’s screen (if you use LibreOffice) etc. in a multi-display setup.
In 2016 I started by introducing a hidden setting in xfce4-notifyd. This meant your notifications wouldn’t pop up during presentations on external displays anymore (because the default setting before was to follow the mouse pointer’s location). I personally needed/wanted this and it felt like an easy fix.
In 2017 I added the feature to xfce4-panel. Before that you had to either hard-code the location of the panels or use the “Automatic” setting, which always puts your panels at the left top part of the screen (x=0, y=0). In combination with the display settings option this provided an easy way of moving the panel around and keeping it on certain displays even when connecting new additional ones.
In late 2018 I started working on the big missing piece of the puzzle, which is xfdesktop. At the time of writing, my patches are still in review in this bugreport (testing welcome!), but things work ok or at least well enough to give me hope that we will see this in the next development release.
In parallel to the xfdesktop patch I also picked up the display settings dialog again after gathering some input from friends at work and decided to pull in all the information about the usage and configuration of the “Primary Display”, as its settings are spread across several components and dialogs. The point of this popover is to show the current configuration status as well as adding a shorthand for accessing all those settings dialogs.
I also went with a new way of highlighting which display is configured as “Primary Display” that is hopefully more easily understandable than the panel I added in the 4.13.5 release. The star is shown both in the displays widget as well as in the properties list of each display, so users can easily visually match which display is primary and what that means.