#[repr(transparent)]pub struct Resource { /* private fields */ }Expand description
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 (deprecated since gdk-pixbuf 2.32) 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 of 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.
to-pixdata has been deprecated since gdk-pixbuf 2.32, as Resource
supports embedding modern image formats just as well. Instead of using it,
embed a PNG or SVG file in your Resource.
json-stripblanks which will use the json-glib-format command to strip
ignorable whitespace from the JSON file. For this to work, the
JSON_GLIB_FORMAT environment variable must be set to the full path to the
json-glib-format executable, or it must be in the PATH;
otherwise the preprocessing step is skipped. In addition, at least version
1.6 of json-glib-format is required.
Resource files will be exported in the GResource namespace using the
combination of the given prefix and the filename from the file element.
The alias attribute can be used to alter the filename to expose them at a
different location in the resource namespace. Typically, this is used to
include files from a different source directory without exposing the source
directory in the resource namespace, as in the example below.
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>
<file alias="example.css">data/example.css</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
/org/gtk/Example/example.css
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 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
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 resources_open_stream() to stream the data or 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.
Some higher-level APIs, such as GtkApplication, will automatically load
resources from certain well-known paths in the resource namespace as a
convenience. See the documentation for those APIs for details.
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 are created
instead. This requires an explicit initialization call in your application/library, but it works on all platforms,
even on the minor ones where constructors are not supported. (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 are 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 G_SEARCHPATH_SEPARATOR-separated list of substitutions to perform
during resource lookups. It is ignored when running in a setuid process.
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.
Implementations§
source§impl Resource
impl Resource
sourcepub fn from_data(data: &Bytes) -> Result<Resource, Error>
pub fn from_data(data: &Bytes) -> Result<Resource, Error>
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 resources_register().
Note: data must be backed by memory that is at least pointer aligned.
Otherwise this function will internally create a copy of the memory since
GLib 2.56, or in older versions fail and exit the process.
If data is empty or corrupt, ResourceError::Internal will be returned.
data
Returns
source§impl Resource
impl Resource
sourcepub fn enumerate_children(
&self,
path: &str,
lookup_flags: ResourceLookupFlags
) -> Result<Vec<GString>, Error>
pub fn enumerate_children( &self, path: &str, lookup_flags: ResourceLookupFlags ) -> Result<Vec<GString>, Error>
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
Returns
an array of constant strings
sourcepub fn info(
&self,
path: &str,
lookup_flags: ResourceLookupFlags
) -> Result<(usize, u32), Error>
pub fn info( &self, path: &str, lookup_flags: ResourceLookupFlags ) -> Result<(usize, u32), Error>
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
Returns
true if the file was found. false if there were errors
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
sourcepub fn lookup_data(
&self,
path: &str,
lookup_flags: ResourceLookupFlags
) -> Result<Bytes, Error>
pub fn lookup_data( &self, path: &str, lookup_flags: ResourceLookupFlags ) -> Result<Bytes, Error>
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
Returns
glib::Bytes or None on error.
Free the returned object with g_bytes_unref()
sourcepub fn open_stream(
&self,
path: &str,
lookup_flags: ResourceLookupFlags
) -> Result<InputStream, Error>
pub fn open_stream( &self, path: &str, lookup_flags: ResourceLookupFlags ) -> Result<InputStream, Error>
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
Returns
InputStream or None on error.
Free the returned object with g_object_unref()
sourcepub fn load(filename: impl AsRef<Path>) -> Result<Resource, Error>
pub fn load(filename: impl AsRef<Path>) -> Result<Resource, Error>
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 resources_register().
If filename is empty or the data in it is corrupt,
ResourceError::Internal will be returned. If filename doesn’t exist, or
there is an error in reading it, an error from g_mapped_file_new() will be
returned.
filename
the path of a filename to load, in the GLib filename encoding
Returns
Trait Implementations§
source§impl Ord for Resource
impl Ord for Resource
source§impl PartialEq<Resource> for Resource
impl PartialEq<Resource> for Resource
source§impl PartialOrd<Resource> for Resource
impl PartialOrd<Resource> for Resource
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self and other) and is used by the <=
operator. Read moresource§impl StaticType for Resource
impl StaticType for Resource
source§fn static_type() -> Type
fn static_type() -> Type
Self.