Package ch.bailu.gtk.gio

Class Resource

java.lang.Object
ch.bailu.gtk.type.Type
ch.bailu.gtk.type.Pointer
ch.bailu.gtk.type.Record
ch.bailu.gtk.gio.Resource
All Implemented Interfaces:
PointerInterface
public class Resource extends Record
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 #GResource 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 #GResource
supports embedding modern image formats just as well. Instead of using it,
embed a PNG or SVG file in your #GResource.

`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 g_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 #GResource object. The register and unregister functions
register the resource so its files can be accessed using
g_resources_lookup_data().

Once a #GResource 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 #GFile 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 #GResource 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.

https://docs.gtk.org/gio/struct.Resource.html

  • Constructor Details

  • Method Details

    • getClassHandler

      public static ClassHandler getClassHandler()

    • newFromDataResource

      public static Resource newFromDataResource(@Nonnull Bytes data) throws AllocationError
      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().

      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, %G_RESOURCE_ERROR_INTERNAL will be returned.
      Parameters:
      data - A #GBytes
      Returns:
      a new #GResource, or %NULL on error
      Throws:
      AllocationError

    • register

      public void register()
      Registers the resource with the process-global set of resources.
      Once a resource is registered the files in it can be accessed
      with the global resource lookup functions like g_resources_lookup_data().

    • unregister

      public void unregister()
      Unregisters the resource from the process-global set of resources.

    • enumerateChildren

      public Strs enumerateChildren(@Nonnull Str path, int lookup_flags) throws AllocationError
      Returns all the names of children at the specified @path in the resource.
      The return result is a %NULL terminated list of strings which should
      be released with g_strfreev().

      If @path is invalid or does not exist in the #GResource,
      %G_RESOURCE_ERROR_NOT_FOUND will be returned.

      @lookup_flags controls the behaviour of the lookup.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      an array of constant strings
      Throws:
      AllocationError

    • enumerateChildren

      public Strs enumerateChildren(String path, int lookup_flags) throws AllocationError
      Returns all the names of children at the specified @path in the resource.
      The return result is a %NULL terminated list of strings which should
      be released with g_strfreev().

      If @path is invalid or does not exist in the #GResource,
      %G_RESOURCE_ERROR_NOT_FOUND will be returned.

      @lookup_flags controls the behaviour of the lookup.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      an array of constant strings
      Throws:
      AllocationError

    • getInfo

      public boolean getInfo(@Nonnull Str path, int lookup_flags, @Nullable Int64 size, @Nullable Int flags) throws AllocationError
      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.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      size - a location to place the length of the contents of the file, or %NULL if the length is not needed
      flags - a location to place the flags about the file, or %NULL if the length is not needed
      Returns:
      %TRUE if the file was found. %FALSE if there were errors
      Throws:
      AllocationError

    • getInfo

      public boolean getInfo(String path, int lookup_flags, @Nullable Int64 size, @Nullable Int flags) throws AllocationError
      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.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      size - a location to place the length of the contents of the file, or %NULL if the length is not needed
      flags - a location to place the flags about the file, or %NULL if the length is not needed
      Returns:
      %TRUE if the file was found. %FALSE if there were errors
      Throws:
      AllocationError

    • lookupData

      public Bytes lookupData(@Nonnull Str path, int lookup_flags) throws AllocationError
      Looks for a file at the specified @path in the resource and
      returns a #GBytes 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.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      #GBytes or %NULL on error. Free the returned object with g_bytes_unref()
      Throws:
      AllocationError

    • lookupData

      public Bytes lookupData(String path, int lookup_flags) throws AllocationError
      Looks for a file at the specified @path in the resource and
      returns a #GBytes 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.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      #GBytes or %NULL on error. Free the returned object with g_bytes_unref()
      Throws:
      AllocationError

    • openStream

      public InputStream openStream(@Nonnull Str path, int lookup_flags) throws AllocationError
      Looks for a file at the specified @path in the resource and
      returns a #GInputStream that lets you read the data.

      @lookup_flags controls the behaviour of the lookup.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      #GInputStream or %NULL on error. Free the returned object with g_object_unref()
      Throws:
      AllocationError

    • openStream

      public InputStream openStream(String path, int lookup_flags) throws AllocationError
      Looks for a file at the specified @path in the resource and
      returns a #GInputStream that lets you read the data.

      @lookup_flags controls the behaviour of the lookup.
      Parameters:
      path - A pathname inside the resource
      lookup_flags - A #GResourceLookupFlags
      Returns:
      #GInputStream or %NULL on error. Free the returned object with g_object_unref()
      Throws:
      AllocationError

    • ref

      public Resource ref()
      Atomically increments the reference count of @resource by one. This
      function is MT-safe and may be called from any thread.
      Returns:
      The passed in #GResource

    • unref

      public void unref()
      Atomically decrements the reference count of @resource by one. If the
      reference count drops to 0, all memory allocated by the resource is
      released. This function is MT-safe and may be called from any
      thread.

    • load

      public static Resource load(@Nonnull Str filename) throws AllocationError
      Loads a binary resource bundle and creates a #GResource 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().

      If @filename is empty or the data in it is corrupt,
      %G_RESOURCE_ERROR_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.
      Parameters:
      filename - the path of a filename to load, in the GLib filename encoding
      Returns:
      a new #GResource, or %NULL on error
      Throws:
      AllocationError

    • getTypeID

      public static long getTypeID()

    • getParentTypeID

      public static long getParentTypeID()

    • getTypeSize

      public static TypeSystem.TypeSize getTypeSize()

    • getParentTypeSize

      public static TypeSystem.TypeSize getParentTypeSize()

    • getInstanceSize

      public static int getInstanceSize()