This is a for of a-parhom/LightlyShaders, which is a fork of Luwx's LightlyShaders, which in turn is a fork of ShapeCorners.

This fork fixes the infamous bug with blurred corners, though in a somehow hacky way.

Also, it adds the following functionality:

• an additional outer dark outline;
• an option to make dark outline totally black (good with dark themes);
• an option to disable plugin for maximized windows;
• an option to use squircled corners instead of rounded (based on code from ZacharyTalis's ShapeCorners fork).

Warnings:

1. This effect is basically a hack!

Due to the changes introduced in Plasma 5.23 there is no way to draw original shadows under rounded corners any more.

In order to work around that, this fork uses a hack that tries to restore the shadow in the cut out regions based on the data from the closest regions with shadows.

Because of this it may work differently with different themes, corner radiuses or shadow settings. Your mileage may vary.

2. This effect can be resource-hungry!

Thanks to recent changes the performance of this plugin has improved. But depending on your hardware, you still can have performance hit. See issue #6.

Dependencies:

Plasma >= 5.23.

Debian based (Ubuntu, Kubuntu, KDE Neon):

sudo apt install git cmake g++ gettext extra-cmake-modules qttools5-dev libqt5x11extras5-dev libkf5configwidgets-dev libkf5crash-dev libkf5globalaccel-dev libkf5kio-dev libkf5notifications-dev kinit-dev kwin-dev 

Fedora based

sudo dnf install git cmake gcc-c++ extra-cmake-modules qt5-qttools-devel qt5-qttools-static qt5-qtx11extras-devel kf5-kconfigwidgets-devel kf5-kcrash-devel kf5-kguiaddons-devel kf5-kglobalaccel-devel kf5-kio-devel kf5-ki18n-devel kf5-knotifications-devel kf5-kinit-devel kwin-devel qt5-qtbase-devel libepoxy-devel

Arch based

sudo pacman -S git make cmake gcc gettext extra-cmake-modules qt5-tools qt5-x11extras kcrash kglobalaccel kde-dev-utils kio knotifications kinit kwin

OpenSUSE based

sudo zypper install git cmake gcc-c++ extra-cmake-modules libqt5-qttools-devel libqt5-qtx11extras-devel kconfigwidgets-devel kcrash-devel kguiaddons-devel kglobalaccel-devel kio-devel ki18n-devel knotifications-devel kinit-devel kwin5-devel libQt5Gui-devel libQt5OpenGL-devel libepoxy-devel

Manual installation

git clone https://github.com/a-parhom/LightlyShaders

cd LightlyShaders; mkdir qt5build; cd qt5build; cmake ../ -DCMAKE_INSTALL_PREFIX=/usr && make && sudo make install && (kwin_x11 --replace &)