Resource File

Inside the src directory are a collection of files and an images directory. One of the files is an XML file called app_resources.gresource.xml that describes the resources to be included with the application.

The Resource Description

The app_resources.gresource.xml file is an XML resource description file that will be compiled by the build system to produce the app_resources.gresource resource bundle file. This file is then packaged with the application and can be loaded at run-time.

The XML file itself provides a manifest of the data files to be included in the resource bundle.

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/com/example/app_resources">
    <file>images/picture.svg</file>
  </gresource>
</gresources>

Two details are important in this description:

  • The gresource element’s prefix attribute defines the path to the resources for this application. Everything provided by the resource bundle will be accessible inside the virtual /com/example/app_resources directory.
  • The image file we want to include in the resource bundle is specified as a file path inside the file element. The path is relative to the location of the resource description file on the workstation’s file system.

When the app_resources.gresource.xml file is processed by the build system, the tool used to compile it to a bundle locates the image in the directory structure:

  • app_resources.gresource.xml
  • images/
    • picture.svg

Because the file is specified as images/picture.svg in the description, an images directory will be included in the virtual directory structure contained in the app_resources.gresource resource bundle file.

Accessing Resources

Since the resource description included a prefix and the picture.svg image is stored in the images directory, the application needs to combine the prefix and the path in order to access its data:

/com/example/app_resources/images/picture.svg

The use of a prefix means that an application can load multiple resources file from different producers and, in theory, the paths used to access resources should not overlap. This provides a unified way to access resources via a single mechanism.

Summary

In this part of the tutorial we saw that resource description files provide information about the files to be included in a resource bundle, and we looked at how they specify a directory structure for them. More details about this type of file can be found in Application Resources.

Next, we will look at the application’s source code and see how resources are accessed at run-time.