[]Struct gio::Resource

pub struct Resource(_);

Applications and libraries often contain binary or textual data that is really part of the application, rather than user data. For instance GtkBuilder .ui files, splashscreen images, GMenu 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 Resource API and the [glib-compile-resources][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 its 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 are 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.

Resource files can also be marked as compressed. Such files will be included in the resource bundle in a compressed form, but will be automatically uncompressed when the resource is used. This is very useful e.g. for larger text files that are parsed once (or rarely) and then thrown away.

Resource files can also be marked to be preprocessed, by setting the value of the preprocess attribute to a comma-separated list of preprocessing options. The only options currently supported are:

xml-stripblanks which will use the xmllint command to strip ignorable whitespace from the XML file. For this to work, the XMLLINT environment variable must be set to the full path to the xmllint executable, or xmllint must be in the PATH; otherwise the preprocessing step is skipped.

to-pixdata which will use the gdk-pixbuf-pixdata command to convert images to the GdkPixdata format, which allows you to create pixbufs directly using the data inside the resource file, rather than an (uncompressed) copy if it. For this, the gdk-pixbuf-pixdata program must be in the PATH, or the GDK_PIXBUF_PIXDATA environment variable must be set to the full path to the gdk-pixbuf-pixdata executable; otherwise the resource compiler will abort.

Resource bundles are created by the [glib-compile-resources][glib-compile-resources] program which takes an XML file that describes the bundle, and a set of files that the XML references. These are combined into a binary resource bundle.

An example resource description:

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/org/gtk/Example">
    <file>data/splashscreen.png</file>
    <file compressed="true">dialog.ui</file>
    <file preprocess="xml-stripblanks">menumarkup.xml</file>
  </gresource>
</gresources>

This will create a resource bundle with the following files:

/org/gtk/Example/data/splashscreen.png
/org/gtk/Example/dialog.ui
/org/gtk/Example/menumarkup.xml

Note that all resources in the process share the same namespace, so use Java-style path prefixes (like in the above example) to avoid conflicts.

You can then use [glib-compile-resources][glib-compile-resources] to compile the XML to a binary bundle that you can load with Resource::load. However, its more common to use the --generate-source and --generate-header arguments to create a source file and header to link directly into your application. This will generate get_resource(), register_resource() and unregister_resource() functions, prefixed by the --c-name argument passed to [glib-compile-resources][glib-compile-resources]. get_resource() returns the generated Resource object. The register and unregister functions register the resource so its files can be accessed using g_resources_lookup_data.

Once a Resource has been created and registered all the data in it can be accessed globally in the process by using API calls like g_resources_open_stream to stream the data or g_resources_lookup_data to get a direct pointer to the data. You can also use URIs like "resource:///org/gtk/Example/data/splashscreen.png" with File to access the resource data.

There are two forms of the generated source, the default version uses the compiler support for constructor and destructor functions (where available) to automatically create and register the Resource on startup or library load time. If you pass --manual-register two functions to register/unregister the resource is instead created. This requires an explicit initialization call in your application/library, but it works on all platforms, even on the minor ones where this is not available. (Constructor support is available for at least Win32, Mac OS and Linux.)

Note that resource data can point directly into the data segment of e.g. a library, so if you are unloading libraries during runtime you need to be very careful with keeping around pointers to data from a resource, as this goes away when the library is unloaded. However, in practice this is not generally a problem, since most resource accesses is for your own resources, and resource data is often used once, during parsing, and then released.

When debugging a program or testing a change to an installed version, it is often useful to be able to replace resources in the program or library, without recompiling, for debugging or quick hacking and testing purposes.

Since GLib 2.50, it is possible to use the G_RESOURCE_OVERLAYS environment variable to selectively overlay resources with replacements from the filesystem. It is a colon-separated list of substitutions to perform during resource lookups.

A substitution has the form

   /org/gtk/libgtk=/home/desrt/gtk-overlay

The part before the = is the resource subpath for which the overlay applies. The part after is a filesystem path which contains files and subdirectories as you would like to be loaded as resources with the equivalent names.

In the example above, if an application tried to load a resource with the resource path /org/gtk/libgtk/ui/gtkdialog.ui then GResource would check the filesystem path /home/desrt/gtk-overlay/ui/gtkdialog.ui. If a file was found there, it would be used instead. This is an overlay, not an outright replacement, which means that if a file is not found at that path, the built-in version will be used instead. Whiteouts are not currently supported.

Substitutions must start with a slash, and must not contain a trailing slash before the '='. The path after the slash should ideally be absolute, but this is not strictly required. It is possible to overlay the location of a single resource with an individual file.

Methods

impl Resource
[src]

Creates a GResource from a reference to the binary resource bundle. This will keep a reference to data while the resource lives, so the data should not be modified or freed.

If you want to use this resource in the global resource namespace you need to register it with g_resources_register.

data

A glib::Bytes

Returns

a new Resource, or None on error

impl Resource
[src]

Returns all the names of children at the specified path in the resource. The return result is a None terminated list of strings which should be released with g_strfreev.

If path is invalid or does not exist in the Resource, ResourceError::NotFound will be returned.

lookup_flags controls the behaviour of the lookup.

path

A pathname inside the resource

lookup_flags

A ResourceLookupFlags

Returns

an array of constant strings

Looks for a file at the specified path in the resource and if found returns information about it.

lookup_flags controls the behaviour of the lookup.

path

A pathname inside the resource

lookup_flags

A ResourceLookupFlags

size

a location to place the length of the contents of the file, or None if the length is not needed

flags

a location to place the flags about the file, or None if the length is not needed

Returns

true if the file was found. false if there were errors

Looks for a file at the specified path in the resource and returns a glib::Bytes that lets you directly access the data in memory.

The data is always followed by a zero byte, so you can safely use the data as a C string. However, that byte is not included in the size of the GBytes.

For uncompressed resource files this is a pointer directly into the resource bundle, which is typically in some readonly data section in the program binary. For compressed files we allocate memory on the heap and automatically uncompress the data.

lookup_flags controls the behaviour of the lookup.

path

A pathname inside the resource

lookup_flags

A ResourceLookupFlags

Returns

glib::Bytes or None on error. Free the returned object with glib::Bytes::unref

Looks for a file at the specified path in the resource and returns a InputStream that lets you read the data.

lookup_flags controls the behaviour of the lookup.

path

A pathname inside the resource

lookup_flags

A ResourceLookupFlags

Returns

InputStream or None on error. Free the returned object with gobject::ObjectExt::unref

Loads a binary resource bundle and creates a Resource representation of it, allowing you to query it for data.

If you want to use this resource in the global resource namespace you need to register it with g_resources_register.

filename

the path of a filename to load, in the GLib filename encoding

Returns

a new Resource, or None on error

Trait Implementations

impl PartialOrd<Resource> for Resource
[src]

impl Ord for Resource
[src]

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl PartialEq<Resource> for Resource
[src]

impl Clone for Resource

Performs copy-assignment from source. Read more

impl Eq for Resource
[src]

impl Debug for Resource
[src]

impl Hash for Resource
[src]

Feeds a slice of this type into the given [Hasher]. Read more

impl StaticType for Resource

Auto Trait Implementations

impl !Send for Resource

impl !Sync for Resource

Blanket Implementations

impl<T, U> Into for T where
    U: From<T>, 
[src]

impl<T> ToOwned for T where
    T: Clone
[src]

impl<T> From for T
[src]

impl<T, U> TryFrom for T where
    T: From<U>, 
[src]

🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
[src]

impl<T> BorrowMut for T where
    T: ?Sized
[src]

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
[src]

🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<'a, T> ToGlibContainerFromSlice for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
[src]

impl<'a, T> ToGlibContainerFromSlice for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
[src]

impl<'a, T> ToGlibContainerFromSlice for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
[src]

impl<T> ToValue for T where
    T: SetValue + ?Sized
[src]