Handle

[class@Rsvg.Handle] loads an SVG document into memory.

This is the main entry point into the librsvg library. An [class@Rsvg.Handle] is an object that represents SVG data in memory. Your program creates an [class@Rsvg.Handle] from an SVG file, or from a memory buffer that contains SVG data, or in the most general form, from a GInputStream that will provide SVG data.

Librsvg can load SVG images and render them to Cairo surfaces, using a mixture of SVG's [static mode] and [secure static mode]. Librsvg does not do animation nor scripting, and can load references to external data only in some situations; see below.

Librsvg supports reading SVG 1.1 data, and is gradually adding support for features in SVG 2. Librsvg also supports SVGZ files, which are just an SVG stream compressed with the GZIP algorithm.

[static mode]: https://www.w3.org/TR/SVG2/conform.html#static-mode [secure static mode]: https://www.w3.org/TR/SVG2/conform.html#secure-static-mode

The "base file" and resolving references to external files

When you load an SVG, librsvg needs to know the location of the "base file" for it. This is so that librsvg can determine the location of referenced entities. For example, say you have an SVG in /foo/bar/foo.svg and that it has an image element like this:

<image href="resources/foo.png" .../>

In this case, librsvg needs to know the location of the toplevel /foo/bar/foo.svg so that it can generate the appropriate reference to /foo/bar/resources/foo.png.

Security and locations of referenced files

When processing an SVG, librsvg will only load referenced files if they are in the same directory as the base file, or in a subdirectory of it. That is, if the base file is /foo/bar/baz.svg, then librsvg will only try to load referenced files (from SVG's <image> element, for example, or from content included through XML entities) if those files are in /foo/bar/<anything> or in /foo/bar/<anything>\/.../<anything>. This is so that malicious SVG files cannot include files that are in a directory above.

The full set of rules for deciding which URLs may be loaded is as follows; they are applied in order. A referenced URL will not be loaded as soon as one of these rules fails:

1. All data: URLs may be loaded. These are sometimes used to include raster image data, encoded as base-64, directly in an SVG file.

2. All other URL schemes in references require a base URL. For example, this means that if you load an SVG with [ctor@Rsvg.Handle.new_from_data] without calling [method@Rsvg.Handle.set_base_uri], then any referenced files will not be allowed (e.g. raster images to be loaded from other files will not work).

3. If referenced URLs are absolute, rather than relative, then they must have the same scheme as the base URL. For example, if the base URL has a file scheme, then all URL references inside the SVG must also have the file scheme, or be relative references which will be resolved against the base URL.

4. If referenced URLs have a resource scheme, that is, if they are included into your binary program with GLib's resource mechanism, they are allowed to be loaded (provided that the base URL is also a resource, per the previous rule).

5. Otherwise, non-file schemes are not allowed. For example, librsvg will not load http resources, to keep malicious SVG data from "phoning home".

6. A relative URL must resolve to the same directory as the base URL, or to one of its subdirectories. Librsvg will canonicalize filenames, by removing ".." path components and resolving symbolic links, to decide whether files meet these conditions.

Loading an SVG with GIO

This is the easiest and most resource-efficient way of loading SVG data into an [class@Rsvg.Handle].

If you have a GFile that stands for an SVG file, you can simply call [ctor@Rsvg.Handle.new_from_gfile_sync] to load an [class@Rsvg.Handle] from it.

Alternatively, if you have a GInputStream, you can use [ctor@Rsvg.Handle.new_from_stream_sync].

Both of those methods allow specifying a GCancellable, so the loading process can be cancelled from another thread.

Loading an SVG from memory

If you already have SVG data in a byte buffer in memory, you can create a memory input stream with [ctor@Gio.MemoryInputStream.new_from_data] and feed that to [ctor@Rsvg.Handle.new_from_stream_sync].

Note that in this case, it is important that you specify the base_file for the in-memory SVG data. Librsvg uses the base_file to resolve links to external content, like raster images.

Loading an SVG without GIO

You can load an [class@Rsvg.Handle] from a simple filename or URI with [ctor@Rsvg.Handle.new_from_file]. Note that this is a blocking operation; there is no way to cancel it if loading a remote URI takes a long time. Also, note that this method does not let you specify [flags@Rsvg.HandleFlags].

Otherwise, loading an SVG without GIO is not recommended, since librsvg will need to buffer your entire data internally before actually being able to parse it. The deprecated way of doing this is by creating a handle with [ctor@Rsvg.Handle.new] or [ctor@Rsvg.Handle.new_with_flags], and then using [method@Rsvg.Handle.write] and [method@Rsvg.Handle.close] to feed the handle with SVG data. Still, please try to use the GIO stream functions instead.

Resolution of the rendered image (dots per inch, or DPI)

SVG images can contain dimensions like "5cm" or "2pt" that must be converted from physical units into device units. To do this, librsvg needs to know the actual dots per inch (DPI) of your target device. You can call [method@Rsvg.Handle.set_dpi] or [method@Rsvg.Handle.set_dpi_x_y] on an [class@Rsvg.Handle] to set the DPI before rendering it.

Rendering

The preferred way to render a whole SVG document is to use [method@Rsvg.Handle.render_document]. Please see its documentation for details.

API ordering

Due to the way the librsvg API evolved over time, an [class@Rsvg.Handle] object is available for use as soon as it is constructed. However, not all of its methods can be called at any time. For example, an [class@Rsvg.Handle] just constructed with [ctor@Rsvg.Handle.new] is not loaded yet, and it does not make sense to call [method@Rsvg.Handle.render_document] on it just at that point.

The documentation for the available methods in [class@Rsvg.Handle] may mention that a particular method is only callable on a "fully loaded handle". This means either:

* The handle was loaded with [method@Rsvg.Handle.write] and [method@Rsvg.Handle.close], and those functions returned no errors.

* The handle was loaded with [method@Rsvg.Handle.read_stream_sync] and that function returned no errors.

Before librsvg 2.46, the library did not fully verify that a handle was in a fully loaded state for the methods that require it. To preserve compatibility with old code which inadvertently called the API without checking for errors, or which called some methods outside of the expected order, librsvg will just emit a g_critical() message in those cases.

New methods introduced in librsvg 2.46 and later will check for the correct ordering, and panic if they are called out of order. This will abort the program as if it had a failed assertion.

class Handle : ObjectG {

protected

RsvgHandle* rsvgHandle;

RsvgHandle* getHandleStruct(bool transferOwnership);

void* getStruct();

this(RsvgHandle* rsvgHandle, bool ownedRef);

static GType getType();

this();

this(ubyte[] data);

this(string filename);

this(FileIF file, RsvgHandleFlags flags, Cancellable cancellable);

this(InputStream inputStream, FileIF baseFile, RsvgHandleFlags flags, Cancellable cancellable);

this(RsvgHandleFlags flags);

bool close();

void free();

string getBaseUri();

string getDesc();

void getDimensions(RsvgDimensionData dimensionData);

bool getDimensionsSub(RsvgDimensionData dimensionData, string id);

bool getGeometryForElement(string id, RsvgRectangle outInkRect, RsvgRectangle outLogicalRect);

bool getGeometryForLayer(string id, RsvgRectangle* viewport, RsvgRectangle outInkRect, RsvgRectangle outLogicalRect);

void getIntrinsicDimensions(bool outHasWidth, RsvgLength outWidth, bool outHasHeight, RsvgLength outHeight, bool outHasViewbox, RsvgRectangle outViewbox);

bool getIntrinsicSizeInPixels(double outWidth, double outHeight);

string getMetadata();

Pixbuf getPixbuf();

Pixbuf getPixbufSub(string id);

bool getPositionSub(RsvgPositionData positionData, string id);

string getTitle();

bool hasSub(string id);

void internalSetTesting(bool testing);

bool readStreamSync(InputStream stream, Cancellable cancellable);

bool renderCairo(Context cr);

bool renderCairoSub(Context cr, string id);

bool renderDocument(Context cr, RsvgRectangle* viewport);

bool renderElement(Context cr, string id, RsvgRectangle* elementViewport);

bool renderLayer(Context cr, string id, RsvgRectangle* viewport);

void setBaseGfile(FileIF baseFile);

void setBaseUri(string baseUri);

void setDpi(double dpi);

void setDpiXY(double dpiX, double dpiY);

void setSizeCallback(RsvgSizeFunc sizeFunc, void* userData, GDestroyNotify userDataDestroy);

bool setStylesheet(ubyte[] css);

bool write(char[] buf);

static void cleanup();

static void setDefaultDpi(double dpi);

static void setDefaultDpiXY(double dpiX, double dpiY);

}

Constructors

this this(RsvgHandle* rsvgHandle, bool ownedRef): Sets our main struct and passes it to the parent class.
this this(): Returns a new rsvg handle. Must be freed with [method@GObject.Object.unref]. This handle can be used to load an image.
this this(ubyte[] data): Loads the SVG specified by @data. Note that this function creates an [class@Rsvg.Handle] without a base URL, and without any [flags@Rsvg.HandleFlags]. If you need these, use [ctor@Rsvg.Handle.new_from_stream_sync] instead by creating a [class@Gio.MemoryInputStream] from your data.
this this(string filename): Loads the SVG specified by @file_name. Note that this function, like [ctor@Rsvg.Handle.new], does not specify any loading flags for the resulting handle. If you require the use of [flags@Rsvg.HandleFlags], use [ctor@Rsvg.Handle.new_from_gfile_sync].
this this(FileIF file, RsvgHandleFlags flags, Cancellable cancellable): Creates a new [class@Rsvg.Handle] for @file.
this this(InputStream inputStream, FileIF baseFile, RsvgHandleFlags flags, Cancellable cancellable): Creates a new [class@Rsvg.Handle] for @stream.
this this(RsvgHandleFlags flags): Creates a new [class@Rsvg.Handle] with flags @flags. After calling this function, you can feed the resulting handle with SVG data by using [method@Rsvg.Handle.read_stream_sync].

Members

Functions

close bool close(): This is used after calling [method@Rsvg.Handle.write] to indicate that there is no more data to consume, and to start the actual parsing of the SVG document. The only reason to call this function is if you use use [method@Rsvg.Handle.write] to feed data into the @handle; if you use the other methods like [ctor@Rsvg.Handle.new_from_file] or [method@Rsvg.Handle.read_stream_sync], then you do not need to call this function.
free void free(): Frees @handle.
getBaseUri string getBaseUri(): Gets the base uri for this [class@Rsvg.Handle].
getDesc string getDesc()
getDimensions void getDimensions(RsvgDimensionData dimensionData): Get the SVG's size. Do not call from within the size_func callback, because an infinite loop will occur.
getDimensionsSub bool getDimensionsSub(RsvgDimensionData dimensionData, string id): Get the size of a subelement of the SVG file. Do not call from within the size_func callback, because an infinite loop will occur.
getGeometryForElement bool getGeometryForElement(string id, RsvgRectangle outInkRect, RsvgRectangle outLogicalRect): Computes the ink rectangle and logical rectangle of a single SVG element.
getGeometryForLayer bool getGeometryForLayer(string id, RsvgRectangle* viewport, RsvgRectangle outInkRect, RsvgRectangle outLogicalRect): Computes the ink rectangle and logical rectangle of an SVG element, or the whole SVG, as if the whole SVG were rendered to a specific viewport.
getHandleStruct RsvgHandle* getHandleStruct(bool transferOwnership): Get the main Gtk struct
getIntrinsicDimensions void getIntrinsicDimensions(bool outHasWidth, RsvgLength outWidth, bool outHasHeight, RsvgLength outHeight, bool outHasViewbox, RsvgRectangle outViewbox): In simple terms, queries the width, height, and viewBox attributes in an SVG document.
getIntrinsicSizeInPixels bool getIntrinsicSizeInPixels(double outWidth, double outHeight): Converts an SVG document's intrinsic dimensions to pixels, and returns the result.
getMetadata string getMetadata()
getPixbuf Pixbuf getPixbuf(): Returns the pixbuf loaded by @handle. The pixbuf returned will be reffed, so the caller of this function must assume that ref.
getPixbufSub Pixbuf getPixbufSub(string id): Creates a GdkPixbuf the same size as the entire SVG loaded into @handle, but only renders the sub-element that has the specified @id (and all its sub-sub-elements recursively). If @id is NULL, this function renders the whole SVG.
getPositionSub bool getPositionSub(RsvgPositionData positionData, string id): Get the position of a subelement of the SVG file. Do not call from within the size_func callback, because an infinite loop will occur.
getStruct void* getStruct(): the main Gtk struct as a void*
getTitle string getTitle()
hasSub bool hasSub(string id): Checks whether the element @id exists in the SVG document.
internalSetTesting void internalSetTesting(bool testing): Do not call this function. This is intended for librsvg's internal test suite only.
readStreamSync bool readStreamSync(InputStream stream, Cancellable cancellable): Reads @stream and writes the data from it to @handle.
renderCairo bool renderCairo(Context cr): Draws a loaded SVG handle to a Cairo context. Please try to use [method@Rsvg.Handle.render_document] instead, which allows you to pick the size at which the document will be rendered.
renderCairoSub bool renderCairoSub(Context cr, string id): Renders a single SVG element in the same place as for a whole SVG document (a "subset" of the document). Please try to use [method@Rsvg.Handle.render_layer] instead, which allows you to pick the size at which the document with the layer will be rendered.
renderDocument bool renderDocument(Context cr, RsvgRectangle* viewport): Renders the whole SVG document fitted to a viewport.
renderElement bool renderElement(Context cr, string id, RsvgRectangle* elementViewport): Renders a single SVG element to a given viewport.
renderLayer bool renderLayer(Context cr, string id, RsvgRectangle* viewport): Renders a single SVG element in the same place as for a whole SVG document.
setBaseGfile void setBaseGfile(FileIF baseFile): Set the base URI for @handle from @file.
setBaseUri void setBaseUri(string baseUri): Set the base URI for this SVG.
setDpi void setDpi(double dpi): Sets the DPI at which the @handle will be rendered. Common values are 75, 90, and 300 DPI.
setDpiXY void setDpiXY(double dpiX, double dpiY): Sets the DPI at which the @handle will be rendered. Common values are 75, 90, and 300 DPI.
setSizeCallback void setSizeCallback(RsvgSizeFunc sizeFunc, void* userData, GDestroyNotify userDataDestroy): Sets the sizing function for the @handle, which can be used to override the size that librsvg computes for SVG images. The @size_func is called from the following functions:
setStylesheet bool setStylesheet(ubyte[] css): Sets a CSS stylesheet to use for an SVG document.
write bool write(char[] buf): Loads the next @count bytes of the image. You can call this function multiple times until the whole document is consumed; then you must call [method@Rsvg.Handle.close] to actually parse the document.

Static functions

cleanup void cleanup(): This function does nothing.
getType GType getType()
setDefaultDpi void setDefaultDpi(double dpi): Do not use this function. Create an [class@Rsvg.Handle] and call [method@Rsvg.Handle.set_dpi] on it instead.
setDefaultDpiXY void setDefaultDpiXY(double dpiX, double dpiY): Do not use this function. Create an [class@Rsvg.Handle] and call [method@Rsvg.Handle.set_dpi_x_y] on it instead.

Variables

rsvgHandle RsvgHandle* rsvgHandle;: the main Gtk struct

Inherited Members

From ObjectG

gObject GObject* gObject;: the main Gtk struct
ownedRef bool ownedRef;: Undocumented in source.
getObjectGStruct GObject* getObjectGStruct(bool transferOwnership): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
isGcRoot bool isGcRoot;: Undocumented in source.
signals DClosure[gulong] signals;: Undocumented in source.
destroyNotify void destroyNotify(ObjectG obj): Undocumented in source. Be warned that the author may not have intended to support it.
toggleNotify void toggleNotify(ObjectG obj, GObject* object, int isLastRef): Undocumented in source. Be warned that the author may not have intended to support it.
~this ~this(): Undocumented in source.
opCast T opCast()
getDObject RT getDObject(U obj, bool ownedRef): Gets a D Object from the objects table of associations.
removeGcRoot void removeGcRoot(): Undocumented in source. Be warned that the author may not have intended to support it.
setProperty void setProperty(string propertyName, T value)
unref deprecated void unref(ObjectG obj): Undocumented in source. Be warned that the author may not have intended to support it.
doref deprecated ObjectG doref(ObjectG obj): Undocumented in source. Be warned that the author may not have intended to support it.
addOnNotify gulong addOnNotify(void delegate(ParamSpec, ObjectG) dlg, string property, ConnectFlags connectFlags): The notify signal is emitted on an object when one of its properties has been changed. Note that getting this signal doesn't guarantee that the value of the property has actually changed, it may also be emitted when the setter for the property is called to reinstate the previous value.
getType GType getType()
compatControl size_t compatControl(size_t what, void* data)
interfaceFindProperty ParamSpec interfaceFindProperty(TypeInterface gIface, string propertyName): Find the #GParamSpec with the given name for an interface. Generally, the interface vtable passed in as @g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().
interfaceInstallProperty void interfaceInstallProperty(TypeInterface gIface, ParamSpec pspec): Add a property to an interface; this is only useful for interfaces that are added to GObject-derived types. Adding a property to an interface forces all objects classes with that interface to have a compatible property. The compatible property could be a newly created #GParamSpec, but normally g_object_class_override_property() will be used so that the object class only needs to provide an implementation and inherits the property description, default value, bounds, and so forth from the interface property.
interfaceListProperties ParamSpec[] interfaceListProperties(TypeInterface gIface): Lists the properties of an interface.Generally, the interface vtable passed in as @g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().
addToggleRef void addToggleRef(GToggleNotify notify, void* data): Increases the reference count of the object by one and sets a callback to be called when all other references to the object are dropped, or when this is already the last reference to the object and another reference is established.
addWeakPointer void addWeakPointer(void* weakPointerLocation): Adds a weak reference from weak_pointer to @object to indicate that the pointer located at @weak_pointer_location is only valid during the lifetime of @object. When the @object is finalized, @weak_pointer will be set to %NULL.
bindProperty Binding bindProperty(string sourceProperty, ObjectG target, string targetProperty, GBindingFlags flags): Creates a binding between @source_property on @source and @target_property on @target.
bindPropertyFull Binding bindPropertyFull(string sourceProperty, ObjectG target, string targetProperty, GBindingFlags flags, GBindingTransformFunc transformTo, GBindingTransformFunc transformFrom, void* userData, GDestroyNotify notify): Complete version of g_object_bind_property().
bindPropertyWithClosures Binding bindPropertyWithClosures(string sourceProperty, ObjectG target, string targetProperty, GBindingFlags flags, Closure transformTo, Closure transformFrom): Creates a binding between @source_property on @source and @target_property on @target, allowing you to set the transformation functions to be used by the binding.
dupData void* dupData(string key, GDuplicateFunc dupFunc, void* userData): This is a variant of g_object_get_data() which returns a 'duplicate' of the value. @dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object.
dupQdata void* dupQdata(GQuark quark, GDuplicateFunc dupFunc, void* userData): This is a variant of g_object_get_qdata() which returns a 'duplicate' of the value. @dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object.
forceFloating void forceFloating(): This function is intended for #GObject implementations to re-enforce a floating[floating-ref] object reference. Doing this is seldom required: all #GInitiallyUnowneds are created with a floating reference which usually just needs to be sunken by calling g_object_ref_sink().
freezeNotify void freezeNotify(): Increases the freeze count on @object. If the freeze count is non-zero, the emission of "notify" signals on @object is stopped. The signals are queued until the freeze count is decreased to zero. Duplicate notifications are squashed so that at most one #GObject::notify signal is emitted for each property modified while the object is frozen.
getData void* getData(string key): Gets a named field from the objects table of associations (see g_object_set_data()).
getProperty void getProperty(string propertyName, Value value): Gets a property of an object.
getQdata void* getQdata(GQuark quark): This function gets back user data pointers stored via g_object_set_qdata().
getValist void getValist(string firstPropertyName, void* varArgs): Gets properties of an object.
getv void getv(string[] names, Value[] values): Gets @n_properties properties for an @object. Obtained properties will be set to @values. All properties must be valid. Warnings will be emitted and undefined behaviour may result if invalid properties are passed in.
isFloating bool isFloating(): Checks whether @object has a floating[floating-ref] reference.
notify void notify(string propertyName): Emits a "notify" signal for the property @property_name on @object.
notifyByPspec void notifyByPspec(ParamSpec pspec): Emits a "notify" signal for the property specified by @pspec on @object.
doref alias doref = ref_: Undocumented in source.
ref_ ObjectG ref_(): Increases the reference count of @object.
refSink ObjectG refSink(): Increase the reference count of @object, and possibly remove the floating[floating-ref] reference, if @object has a floating reference.
removeToggleRef void removeToggleRef(GToggleNotify notify, void* data): Removes a reference added with g_object_add_toggle_ref(). The reference count of the object is decreased by one.
removeWeakPointer void removeWeakPointer(void* weakPointerLocation): Removes a weak reference from @object that was previously added using g_object_add_weak_pointer(). The @weak_pointer_location has to match the one used with g_object_add_weak_pointer().
replaceData bool replaceData(string key, void* oldval, void* newval, GDestroyNotify destroy, GDestroyNotify oldDestroy): Compares the user data for the key @key on @object with @oldval, and if they are the same, replaces @oldval with @newval.
replaceQdata bool replaceQdata(GQuark quark, void* oldval, void* newval, GDestroyNotify destroy, GDestroyNotify oldDestroy): Compares the user data for the key @quark on @object with @oldval, and if they are the same, replaces @oldval with @newval.
runDispose void runDispose(): Releases all references to other objects. This can be used to break reference cycles.
setData void setData(string key, void* data): Each object carries around a table of associations from strings to pointers. This function lets you set an association.
setDataFull void setDataFull(string key, void* data, GDestroyNotify destroy): Like g_object_set_data() except it adds notification for when the association is destroyed, either by setting it to a different value or when the object is destroyed.
setProperty void setProperty(string propertyName, Value value): Sets a property on an object.
setQdata void setQdata(GQuark quark, void* data): This sets an opaque, named pointer on an object. The name is specified through a #GQuark (retrieved e.g. via g_quark_from_static_string()), and the pointer can be gotten back from the @object with g_object_get_qdata() until the @object is finalized. Setting a previously set user data pointer, overrides (frees) the old pointer set, using #NULL as pointer essentially removes the data stored.
setQdataFull void setQdataFull(GQuark quark, void* data, GDestroyNotify destroy): This function works like g_object_set_qdata(), but in addition, a void (*destroy) (gpointer) function may be specified which is called with @data as argument when the @object is finalized, or the data is being overwritten by a call to g_object_set_qdata() with the same @quark.
setValist void setValist(string firstPropertyName, void* varArgs): Sets properties on an object.
setv void setv(string[] names, Value[] values): Sets @n_properties properties for an @object. Properties to be set will be taken from @values. All properties must be valid. Warnings will be emitted and undefined behaviour may result if invalid properties are passed in.
stealData void* stealData(string key): Remove a specified datum from the object's data associations, without invoking the association's destroy handler.
stealQdata void* stealQdata(GQuark quark): This function gets back user data pointers stored via g_object_set_qdata() and removes the @data from object without invoking its destroy() function (if any was set). Usually, calling this function is only required to update user data pointers with a destroy notifier, for example: |[ void object_add_to_user_list (GObject *object, const gchar *new_string) { // the quark, naming the object data GQuark quark_string_list = g_quark_from_static_string ("my-string-list"); // retrieve the old string list GList *list = g_object_steal_qdata (object, quark_string_list);
takeRef ObjectG takeRef(): If @object is floating, sink it. Otherwise, do nothing.
thawNotify void thawNotify(): Reverts the effect of a previous call to g_object_freeze_notify(). The freeze count is decreased on @object and when it reaches zero, queued "notify" signals are emitted.
unref void unref(): Decreases the reference count of @object. When its reference count drops to 0, the object is finalized (i.e. its memory is freed).
watchClosure void watchClosure(Closure closure): This function essentially limits the life time of the @closure to the life time of the object. That is, when the object is finalized, the @closure is invalidated by calling g_closure_invalidate() on it, in order to prevent invocations of the closure with a finalized (nonexisting) object. Also, g_object_ref() and g_object_unref() are added as marshal guards to the @closure, to ensure that an extra reference count is held on @object during invocation of the @closure. Usually, this function will be called on closures that use this @object as closure data.
weakRef void weakRef(GWeakNotify notify, void* data): Adds a weak reference callback to an object. Weak references are used for notification when an object is disposed. They are called "weak references" because they allow you to safely hold a pointer to an object without calling g_object_ref() (g_object_ref() adds a strong reference, that is, forces the object to stay alive).
weakUnref void weakUnref(GWeakNotify notify, void* data): Removes a weak reference callback to an object.
clearObject void clearObject(ObjectG objectPtr): Clears a reference to a #GObject.