GResource ​

GResource is a resource bundle that includes application data like:

• UI files
• Icons
• CSS

There are quite a few ways to bundle such assets in Crystal (including manually loading them using macros), however GResource offers something important that they don't - being integrated with GTK.

That allows you to e.g. directly set css & icons to those loaded from the bundle (Widget#icon_name = "path/in/bundle/icon.svg").

Getting Started ​

• Create a data/APP_ID.gresource.xml with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/path/for/bundle">
    <file compressed="true">css/style.css</file>
    <file compressed="true" preprocess="xml-stripblanks">icons/my_app.svg</file>
    <file compressed="true" preprocess="xml-stripblanks">ui/my_app.ui</file>
  </gresource>
</gresources>

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/path/for/bundle">
    <file compressed="true">css/style.css</file>
    <file compressed="true" preprocess="xml-stripblanks">icons/my_app.svg</file>
    <file compressed="true" preprocess="xml-stripblanks">ui/my_app.ui</file>
  </gresource>
</gresources>

• That will bundle the following files: data/css/style.css, icons/my_app.svg & ui/my_app.ui, compress them and strip their whitespace.

• You should replace /path/for/bundle with the path you want, usually the APP_ID (e.g. dev.geopjr.My_app => /dev/geopjr/My_app).

• And now you can load them as if they are at that location, e.g.:

Gtk::CssProvider#load_from_resource("/dev/geopjr/My_app/css/style.css")`.

Gtk::CssProvider#load_from_resource("/dev/geopjr/My_app/css/style.css")`.

Debugger should also be able to list them under Global > Resources.

Creating & Loading the binary ​

You can either create and load it manually or use the Gio#register_resource macro that does both of them for you:

Gio#register_resource ​

We just call it in prerequisites:

Gio.register_resource("data/dev.geopjr.My_app.gresource.xml", "data")

Gio.register_resource("data/dev.geopjr.My_app.gresource.xml", "data")

Manually ​

Creating the binary ​

The binary is being created with the use of an external tool, glib-compile-resources.

The full command is:

$ glib-compile-resources --sourcedir BASE_FOLDER --target PATH/TO/COMPILED.gresource PATH/TO/FILE.gresource.xml

$ glib-compile-resources --sourcedir BASE_FOLDER --target PATH/TO/COMPILED.gresource PATH/TO/FILE.gresource.xml

Having the above locations as examples, it should look like:

$ glib-compile-resources --sourcedir data --target data/dev.geopjr.My_app.gresource data/dev.geopjr.My_app.gresource.xml

$ glib-compile-resources --sourcedir data --target data/dev.geopjr.My_app.gresource data/dev.geopjr.My_app.gresource.xml

Loading the binary ​

There should now be a data/dev.geopjr.My_app.gresource binary.

We load it in memory using macros and then register it in prerequisites. Follow Gio#register_resource's source.