In Plasma (or just KWin), if you want to have window decorations, of an application that doesn’t like having anything outside its own, behave in a uniform way that you configured in your setup, you launch yourself the “Window Rules” by either
- Clicking on the titlebar of some normal window and picking “More Actions” and “Configure Special Window Settings” or “Configure Special Application Settings”, then going the arrow back to get out of creating a new rule or customizing an existing one (the window name, however, will remain referring to which fo the two options did you pick), or, more reasonably,
- Going to Plasma System Settings, from there under Workspace to Window Management, and picking Window Rules.
There, you use “Add new…” to create a new rule, use the Detect Window Properties tool to pick a window and select what scope do you want, consider the “matching whole window class” selector at random (occasionally giving it more thought), and then picking “No titlebar and frame” and setting it to “Force” with “No”, then picking “Instantly” above the Apply button and clicking Apply.
This lets you comfortably shade/unshade (feature only active in X11… https://bugs.kde.org/show_bug.cgi?id=377162) a maximized jetbrains-idea or code code with your mouse scroll wheel if you configured your KWin so; you may also want to do the same for “Ignore global shortcuts” so that your Alt-drag works for moving and resizing these even if they like having Alt for themselves.
Descent into the Microsoft Edge madness
But then if you do the same for Microsoft Edge…
Say you had “GTK+” picked in the “GTK+/Light/Dark” picker. At first attempt applying the Force rule may have you see an MS Edge floating anchored surrounded by one centimeter of padding all around — within a frame of proper decorations — as if to let it render its transparent shadow gradient.
Some search result told me I should disable “Show Windows 11 Visual effects in browser” option in flags. It was supposed to show me an option in Appearance settings, but didn’t.
Later I found that if I click Edge’s own titlebar, there is an action to “USe system title bar and borders”. Every time throughout all my next steps I kept attempting to have it do the thing.
Then I fiddled with the “GTK+/Light/Dark” theme picker in Appearance… and it turned out that switching to Light or Dark reliably makes all the Edge windows (including PWA) about once centimeter larger towards each side.
At this point applying the Window Rule no longer does anything. Not even rules like blocking compositing and restricting geometry cause anything else than at most odd glitches of transparency, replacing transparency with black/garbage or some really old transparency in between tabs (I switched to horizontal tabs in my attempts). Just a brief few-millimiter black/garbage frame around the windows for a few seconds shows it does something.
Setting “custom_chrome_frame” to false under “browser” in the “Preferences” file within the profile directory, as per another online advice, also didn’t show any difference.
Found nothing about currently existing CLI switches to deal with this.
I then tried pressing Alt+F3 to bring up Window Operations Menu of KWin… saw “No Border” checked and greyed out in there.
Maybe I will have more attempts after I restart Plasma later, for now I feel done with this.