To use this option, make sure the GTK 3 and Cairo development files
are installed, and configure Emacs with the option '--with-pgtk'.
Unlike the default X and GTK build, the resulting Emacs binary will
-work on any underlying window system supported by GDK, such as
-Wayland and Broadway.
+work on any underlying window system supported by GDK, such as Wayland
+and Broadway. We do not recommend that you use this configuration,
+unless you are running a window system that's supported by GDK other
+than X. Running this configuration on X is known to have problems,
+such as undesirable frame positioning and keyboard input of sequences
+such as "C-;" and "C-S-u".
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** The docstrings of preloaded files are not in "etc/DOC" any more.