Remove a boatload of "or %NULL" from nullable parameters
and return values. gi-docgen generates suitable text from
the annotation that we don't need to duplicate.
This adds a few missing nullable annotations too.
In GTK 3, it was pretty much always better to use
gtk_builder_new_from_whatever() rather than
gtk_builder_add_from_whatever(). But in GTK 4, this is no longer
generally true. Let's add some context on when you want to use one or
the other.
With the exception of gtk_buildable_get_id(), those are only used
to construct objects from XML descriptions, which is functionality
internal to GTK.
The API is therefore unlikely to be missed, and keeping it internal
means they can no longer unintentionally shadow object methods in
bindings with less namespacing; for example it's currently ambiguous
whether `infoBar.add_child()` refers to gtk_info_bar_add_child() or
gtk_buildable_add_child().
https://gitlab.gnome.org/GNOME/gtk/-/issues/3191
GtkBuildable's get_name()/set_name() methods may shadow
GtkWidget's methods. Avoid that by renaming the API to
get_buildable_id()/set_buildable_id(), which also reflects
the name of the XML attribute the API refers to.
https://gitlab.gnome.org/GNOME/gtk/-/issues/3191
Use GTK_DEBUG=builder-objects to make GtkBuilder warn
if a named object from a ui files doesn't get claimed
by gtk_builder_get_object(). This is useful for finding
dead wood in .ui files.
Since it's a type with sub-classes, we need to use GTypeInstance (at the
very least), otherwise we won't be able to address each sub-class as
such.
This is similar to how GskRenderNode and GdkEvent are handled, with the
added difficulty that GtkExpression is meant to be used in properties,
in order to be deserialised by GtkBuilder. This requires adding a
GParamSpec sub-class that we can match on from within GtkBuilder,
alongside some convenience API for storing a GtkExpression inside a
GValue.
I couldn't come up with a better way to automatically inherit the scope
in the builder list item factory that didn't involve a magic
incantation in the XML file. And I do not want developers to know magic
incantations to do a thing that should pretty much always be done.
The lightweight inheritance mechanism used for GtkShortcutTrigger is not
going to be usable by bindings, because boxed types cannot have derived
types.
We could use GTypeInstance and derive everything from that, like
GParamSpec, but in the end shortcuts are not really a performance
critical paths, unlike CSS values or render nodes.
If icon lookup fails or if loading it fails later, just always
fall back to the built in image-missing icon. Nobody is handling
missing icons in a sane way anyway.
If you *truly* need to handle missing icons, you need to manually
use gtk_icon_theme_has_icon().
While changing the loading code I also fixed an issue where it
was always passing "png" to pixbuf, now it also handles "xpm" if
that is the filename suffix.
