Gio::Resource och glib-compile-resources

Applications and libraries often contain binary or textual data that is really part of the application, rather than user data. For instance Gtk::Builder .glade files, splashscreen images, Gio::Menu markup xml, CSS files, icons, etc. These are often shipped as files in $datadir/appname, or manually included as literal strings in the code.

The Gio::Resource API and the glib-compile-resources program provide a convenient and efficient alternative to this, which has some nice properties. You maintain the files as normal files, so it's easy to edit them, but during the build the files are combined into a binary bundle that is linked into the executable. This means that loading the resource files is efficient (as they are already in memory, shared with other instances) and simple (no need to check for things like I/O errors or locate the files in the filesystem). It also makes it easier to create relocatable applications.

Resursbuntar skapas av programmet glib-compile-resources som tar en xml-fil som beskriver bunten, och en uppsättning filer som xml-filen refererar till. Dessa kombineras till en binär resursbunt.

Referens för Gio::Resource

Ett exempel:

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/toolbar">
    <file preprocess="xml-stripblanks">toolbar.glade</file>
    <file>rain.png</file>
  </gresource>
</gresources>

You can then use glib-compile-resources to compile the xml to a binary bundle that you can load with Gio::Resource::create_from_file(). However, it's more common to use the --generate-source argument to create a C source file to link directly into your application. E.g.

$ glib-compile-resources --target=resources.c --generate-source toolbar.gresource.xml

Once a Gio::Resource has been created and registered all the data in it can be accessed globally in the process by using API calls like Gio::Resource::open_stream_from_global_resources() to stream the data or Gio::Resource::lookup_data_in_global_resources() to get a direct pointer to the data. You can also use URIs like resource:///toolbar/rain.png with Gio::File to access the resource data.

Ofta behöver du ingen Gio::Resource-instans eftersom resursdata kan läsas in med metoder som Gdk::Pixbuf::create_from_resource(), Gtk::Builder::add_from_resource() och Gtk::Image::set_from_resource().