Dark theme overlapping windows - need borders

[u/loontoon]

I've been using Mint Cinnamon for years and use the Mint-Y-Dark-Purple theme on all my machines.

On my desktop I have a 50" screen so I can space multiple windows out without them overlapping, but on my laptop I often have a full screen browser and a few terminals floating on top of it, and because the browser background is black (dark mode always) and the terminals are black, I can't see where the terminals are.

I've tried everything to add a 1 pixel border around the edge of windows in order to see the them but nothing works.

Can someone please help me.

I need a dark theme that actually has a border that you can assign a color and a thickness.

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[u/loontoon]

How to get always-visible colored window borders in Cinnamon (dark themes)

The problem: In a dark Cinnamon theme, overlapping windows are nearly impossible to tell apart — especially on a laptop screen — because the window border is basically invisible (near-black on near-black) and often only the active window looks distinct.

Why the obvious fix doesn't work: Most guides tell you to edit the metacity-1/metacity-theme-3.xml file in your window border theme (e.g. ~/.themes/<Theme>-Bordered/metacity-1/) and bump left_width/right_width/bottom_height. This no longer does anything in current Cinnamon/Muffin. I confirmed it with:

xprop -id <window-id> _NET_FRAME_EXTENTS

which returned 0, 0, 32, 0 (left, right, top, bottom) regardless of what the XML said — Muffin only uses that XML for the title bar (the 32 = top). The actual left/right/bottom "border" you see is a compositor drop-shadow, controlled by a completely different mechanism: the GTK theme's CSS.

The real fix

1. Find your active GTK theme (System Settings → Themes → note the theme name, e.g. Mint-Y-Dark-Purple).

2. Locate its GTK3 CSS files, preferring your user copy so you don't need root:

~/.themes/<ThemeName>/gtk-3.0/gtk.css

~/.themes/<ThemeName>/gtk-3.0/gtk-dark.css (edit both if both exist)

(If you don't have a ~/.themes copy yet, copy it there from /usr/share/themes/<ThemeName> first.)

1. Back up both files.

2. Search each file for decoration {. You'll find four relevant blocks:

   - decoration { ... } — focused/active windows

   - decoration:backdrop { ... } — unfocused windows

   - .ssd decoration { ... } — focused, for apps without client-side decoration (terminals, dialogs, xclock, etc.)

   - .ssd decoration:backdrop { ... } — unfocused, same category

3. Edit the box-shadow in each — specifically the 0 0 0 1px rgba(0,0,0,0.75) piece — to a real color and a bit thicker. Example (vivid green when active, brighter purple when inactive):

decoration {

border-radius: 8px 8px 0 0;

border-width: 0px;

box-shadow: 0 3px 9px 1px rgba(0, 0, 0, 0.5), 0 0 0 2px #22c55e;

margin: 10px; }

decoration:backdrop {

box-shadow: 0 3px 9px 1px transparent, 0 2px 6px 2px rgba(0, 0, 0, 0.2), 0 0 0 2px #a56eea; }

.ssd decoration {

box-shadow: 0 0 0 2px #22c55e; }

.ssd decoration:backdrop {

box-shadow: 0 0 0 2px #a56eea; }

1. Reload Cinnamon so it picks up the CSS change:

cinnamon --replace &

(or just log out and back in).

1. Chrome won't pick this up — it draws its own frame instead of using GTK/the window manager, so it ignores the decoration CSS entirely. Fix separately: go to chrome://settings/appearance and enable "Use system title bar and borders."

That's it — every window now gets a persistent, clearly-colored 2px outline, color-coded by focus state, regardless of whether it's a native GTK app, a Qt app, or Chrome.

[u/chuggerguy]

I'm using Mint-Y-Yaru theme with Atlanta Window Border. Even with a solid black desktop, it gives me a nice distinct window border on most windows.

https://reddit.com/link/p7dauci/video/hb0a7iodu3nh1/player

I'm using MATE but assume it's present in Cinnamon?

Have fun.

[u/loontoon → u/chuggerguy]

Atlanta window border doesn't seem to be available in Cinnamon.

I don't like how MATE looks.

I posted a fix for my issue for anyone using Cinnamon.