This is to go along with the newly introduced GdkDrop.
This commit includes the necessary updates to the X11, Wayland
and Broadway backends. Other backends have to be updated separately.
This is in preparation of using input streams to show that these
coordinates aren't needed most of the time and can otherwise be saved
during GtkWidget::drag-drop.
Instead of allowing people to pass a uint user-data, insist on them
comparing mime types.
The user data was a uint instead of a pointer anyway, so uniqueness
could not be guaranteed and it caused more issues than it was worth.
And that's ignoring the fact that it basically wasn't used.
Instead, add a function gtk_image_set_icon_size() for the cases where
overriding the icon size is necessary.
Treat icon sizes the same way as pixel sizes, too. So gtk_image_clear()
no longer unsets the icon size.
Instead of returning the icon size with them, make
gtk_image_get_icon_name() and gtk_image_get_gicon() only return the icon
itself.
As a benefit, we can turn them into regular getters that return values
instead of requiring out parameters.
Instead, provide gtk_image_get_icon_size() to query the icon size.
I added a new test function, but didn't actually use it.
No wonder I couldn't reproduce the lifecycle issues with
drag widgets that firefox is experiencing.