New api needs documentation.

The implementation of this function was removed in
44cb3ccf.

These no longer exist.

New api needs documentation.

Add a few things, reword some others.

Some functions have been renamed here.

And document how it works now.

Deemphasize GdkPixbuf in the docs.

Ting-Wei Lan authored Dec 25, 2017 and Matthias Clasen committed Dec 25, 2017

https://bugzilla.gnome.org/show_bug.cgi?id=791926

This has been broken since the inconsistent state
was moved here in 2aea8dfe.

https://bugzilla.gnome.org/show_bug.cgi?id=791927

We no longer have GtkClipboard.

Add the CSS font level 3 properties that we support now
to the docs.

GdkDisplay is missing various annotations, and the introspection scanner
is complaining about it.

The GdkEvent API is missing some gtk-doc stanzas, as well as some
introspection annotations.

The `flags` parameter is missing, and the introspection scanner is
complaining about it.

The documentation and annotations for some of the print API is defined
in platform-specific source files, so we need to ensure we're passing
those files to the introspection scanner in order to avoid warnings, and
to get the appropriate introspected API.

We're missing the gtk-doc stanza, as well as the transfer annotation for
the returned pointer.

Transfer annotations do not apply to integral types.

The new type propagation for g_object_ref() is raising a compiler
warning for an assignment with a different type.

Still fall back in cases we can't handle that way.

This fixes both the wrong headerbar color and the broken border color in
of the circular button in the widget-factory.

This way, we can use the very same coloring program to draw text shadows
of fonts with colored glyphs.

We already ceil() the given float texture sizes here, so if they are
valid, the result should definitely be > 0. Textures with size 0 can't
be properly used, especially not as render targets, where they will
trigger an assertion failure later in a glCheckFramebuffer call.