Florian Müllner authored Sep 08, 2018 and Georges Basile Stavracas Neto committed Nov 26, 2018

It's a UI pattern that has been superseded by client-side decorations,
apps that used to set the hint have generally moved on to headerbars.
Given that and the limitation to server-side decorated X11 windows,
GTK4 removed the client-side API for setting the hint, it's time to
follow suite and retire the feature.

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