gi-gio-0.2.46.13: Gio bindings

CopyrightWill Thompson, Iñaki García Etxebarria and Jonas Platte
LicenseLGPL-2.1
MaintainerIñaki García Etxebarria (garetxe@gmail.com)
Safe HaskellNone
LanguageHaskell2010

GI.Gio.Structs.Resource

Contents

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 #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` 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: |[ version="1.0" encoding="UTF-8"? gresources prefix="/org/gtk/Example" filedatasplashscreen.png<file> compressed="true"dialog.ui/file preprocess="xml-stripblanks"menumarkup.xml/file /gresource /gresources ]|

This will create a resource bundle with the following files: |[ orggtkExampledata/splashscreen.png orggtkExampledialog.ui orggtkExamplemenumarkup.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 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://orggtkExampledata/splashscreen.png" with #GFile 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 #GResource 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.

Synopsis

Exported types

newtype Resource Source

Constructors

Resource (ForeignPtr Resource) 

Instances

BoxedObject Resource Source 

Methods

boxedType :: Resource -> IO GType

((~) * info (ResolveResourceMethod t Resource), MethodInfo * info Resource p) => IsLabel t (Resource -> p) Source 

Methods

fromLabel :: Proxy# Symbol t -> Resource -> p

((~) * info (ResolveResourceMethod t Resource), MethodInfo * info Resource p) => IsLabelProxy t (Resource -> p) Source 

Methods

fromLabelProxy :: Proxy Symbol t -> Resource -> p

((~) (TYPE Lifted) signature (m ()), MonadIO m) => MethodInfo (TYPE Lifted) ResourceUnrefMethodInfo Resource signature Source 
((~) (TYPE Lifted) signature (m Resource), MonadIO m) => MethodInfo (TYPE Lifted) ResourceRefMethodInfo Resource signature Source 
((~) (TYPE Lifted) signature (Text -> [ResourceLookupFlags] -> m InputStream), MonadIO m) => MethodInfo (TYPE Lifted) ResourceOpenStreamMethodInfo Resource signature Source 
((~) (TYPE Lifted) signature (Text -> [ResourceLookupFlags] -> m Bytes), MonadIO m) => MethodInfo (TYPE Lifted) ResourceLookupDataMethodInfo Resource signature Source 
((~) (TYPE Lifted) signature (Text -> [ResourceLookupFlags] -> m (Word64, Word32)), MonadIO m) => MethodInfo (TYPE Lifted) ResourceGetInfoMethodInfo Resource signature Source 
((~) (TYPE Lifted) signature (Text -> [ResourceLookupFlags] -> m [Text]), MonadIO m) => MethodInfo (TYPE Lifted) ResourceEnumerateChildrenMethodInfo Resource signature Source 

noResource :: Maybe Resource Source

Methods

resourceEnumerateChildren

data ResourceEnumerateChildrenMethodInfo Source

Instances

resourceEnumerateChildren :: MonadIO m => Resource -> Text -> [ResourceLookupFlags] -> m [Text] Source

resourceGetInfo

data ResourceGetInfoMethodInfo Source

Instances

resourceGetInfo :: MonadIO m => Resource -> Text -> [ResourceLookupFlags] -> m (Word64, Word32) Source

resourceLoad

resourceLoad :: MonadIO m => [Char] -> m Resource Source

resourceLookupData

data ResourceLookupDataMethodInfo Source

Instances

resourceLookupData :: MonadIO m => Resource -> Text -> [ResourceLookupFlags] -> m Bytes Source

resourceNewFromData

resourceNewFromData :: MonadIO m => Bytes -> m Resource Source

resourceOpenStream

data ResourceOpenStreamMethodInfo Source

Instances

resourceOpenStream :: MonadIO m => Resource -> Text -> [ResourceLookupFlags] -> m InputStream Source

resourceRef

data ResourceRefMethodInfo Source

Instances

resourceRef :: MonadIO m => Resource -> m Resource Source

resourceUnref

data ResourceUnrefMethodInfo Source

Instances

resourceUnref :: MonadIO m => Resource -> m () Source