Panel Separator (Theme) 1.0
Wow. A lot of people have worked on the separator. With my luck someone will already have the ultimate Separator up while I finish typing this.
I created two implementations, Panel Separator (Theme) and Panel Separator (Icon), and I have a third idea in the works. Icon Applets and themable applets both have problems when it comes to separators, but I won't get into that too much here. Zyzz uploaded Separator2 first. Kudos for him and everyone else who put up solutions. Since my implementation of the Separator Icon idea is slightly different than his, I'll put both of my Panel Separators up on different listings. I was going to offer a combo pack, but I don't want to interfere with the UUID listed on this site.
Panel Separator (Theme) takes care of the problem that you may not want all that padding that is caused by using a square icon for a separator. With a themable separator you can use background images, choose your own spacing around the separators, change colors, etc., etc. just by changing css. There's a detailed README file in the zipball. It dteails installation, multiple, separators, theming.
Panel Separator (Theme) which creates a separator by creating a themeable class ".panel-separator". There is a sample theme of the css that creates a white 1px separator as shown in the screenshot. Just extract the applet to the applets folder and copy the contents of stylesheet.sample to the end of your favorite theme.
The example css included in stylesheet.sample.
Just a few notes on theming. You can use background-image: url("your_favorite_picture") instead of background, but width must be >= the width of the picture.
Just as a proof of concept, I tried the ankh icon I used for my Clove-Black theme.
Increase padding to increase the spacing around the separators. Have fun experimenting with the theme. Please let me know what you think of themeable separators. The other concept to make it easier for people to tailor the separator to their needs is to use gsettings, but that's more than I understand right now.
Finally a couple of notes/warnings:
As of now, Cinnamon 1.3.1, you cannot have multiple instances of the same applet. The way to get around that is to rename multiple copies of the same applet so that each folder has a unique identifier, e.g. panel-separator-theme1@mordant23, panel-separator-theme2@mordant23. MAKE SURE YOU CHANGE THE UUID METADATA.JSON file if you do that. more details .
Yes, that means you'll have a nice long list of Separators in Cinnamon Settings if you're like me and need a lot of separators for a crowded panel. But that's ok.
MAKE SURE YOU COPY THE CSS CODE TO THE CINNAMON.CSS FILE IN YOUR THEME FOLDER
I'm not sure how clear the README is on this, but it needs emphasis. Sure you can always rename stylesheet.sample to stylesheet.css, but you'll have to 'Alt+F2', 'r' after you change themes. It's probably easier to just cut and paste the css code to the end of your favorite theme but it's your decision.
SETUP CAN BE TRICKY
If you're like me and you have a lot of separators to organize a very crowded panel, then you're going to either have fun with gsettings to get everything configured or you'll want to increase the padding to make it easier to drag and drop.Cinnamon's drag and drop is still not completely ironed out and trying to maneuver 7 3px wide applets with drag and drop is not fun. It was easier for me to just empty the panel and then just add the applets, including the separators from left to right, in the sequence I wanted. Af ter that it was just a breeze to go to the dconf-editor, use my favorite text editor to cut and paste and change all the centers to left and rights. If you don't know what I mean with all of the dconf stuff, don't worry. If you don't know by now, you probably don't need to.
As always, please let me know if I made any mistakes, especially any infractions against the style guide for the gjs in the applet. I've been using using the applets as a way to teach myself gjs, and I'm still fairly new to this.
Package it for the repos
Make script to make it easier to do multiple installs
Change sample css to have more padding to make it easier to do the initial set up.
Figure out why the gnome-panel-separator icon looks so different as a background image after it's narrowed down to 3px.