(Originally created as https://git.reviewboard.kde.org/r/127162/ - in contrast to the older review, this here only changes the looks of the window, it leaves the kill prompt alone)
I'm absolutely certain there is a bug/wish on bko about this. X only right now, I don't think we have ping/kill infrastructure on Wayland yet?
VDG: When an application freezes and I click the close button, after 2.5s it will desaturate the window, after another 2.5s it will show the "do you want to kill $app" prompt. If I then choose "Wait longer", the prompt closes and the window remains desaturated until the app responds again. I can click the close button again, and get the "do you want to kill $app" prompt again (after 2.5s, for subsequent calls, though). It doesn't happen if you interact with the window in any other way, only the close button "pings" the client.
* Running the timer twice is probably more of a hack, when the client is already marked unresponsive, which halves the timeout when the kill dialog is triggered on subsequent invocations
{F3429932}
Screenshots of a less colorful app (always 10% Saturation), proposals:
125% Brightness (original attempt)
{F3431234}
80% Brightness (I don't really like this, looks mostly like the "dialog parent" effect; while this somewhat teaches people "dark window cannot be interacted with", I don't like it :p)
* Not sure about the "(Not Responding)" part in title bar (also do we have Message.sh for deco?), I chose not to manipulate the client's caption but do it only in the decoration.{F3431316}
150% Brightness (my favorite, Maybe we can improve the lookimplemented in this updated patch, even?
{F3429932}causes separator lines to fully wash out)
{F3431546}