The weird effect on the dialog's backgorund is because the dialog is semi transaparent (which according to my kwin settings probably means its a dialog and not a normal window) and it is disaplayed over a part of the background that has a sharp brightness change.
Screenshot showing the dialog.
The weird effect on the dialog's backgorund is because the dialog is semi transaparent (which according to my kwin settings probably means its a dialog and not a normal window) and it is disaplayed over a part of the background that has a sharp brightness change.