Class
RsvgHandle
Description [src]
class Rsvg.Handle : GObject.Object
{
/* No available fields */
}
RsvgHandle
loads an SVG document into memory.
This is the main entry point into the librsvg library. An RsvgHandle
is an
object that represents SVG data in memory. Your program creates an
RsvgHandle
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.
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:
-
All
data:
URLs may be loaded. These are sometimes used to include raster image data, encoded as base-64, directly in an SVG file. -
URLs with queries (“?”) or fragment identifiers (“#”) are not allowed.
-
All URL schemes other than data: in references require a base URL. For example, this means that if you load an SVG with
rsvg_handle_new_from_data()
without callingrsvg_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). -
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 thefile
scheme, or be relative references which will be resolved against the base URL. -
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 aresource
, per the previous rule). -
Otherwise, non-
file
schemes are not allowed. For example, librsvg will not loadhttp
resources, to keep malicious SVG data from “phoning home”. -
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 RsvgHandle
.
If you have a GFile
that stands for an SVG file, you can simply call
rsvg_handle_new_from_gfile_sync()
to load an RsvgHandle
from it.
Alternatively, if you have a GInputStream
, you can use
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 g_memory_input_stream_new_from_data()
and feed that
to 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 RsvgHandle
from a simple filename or URI with
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 RsvgHandleFlags
.
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
rsvg_handle_new()
or rsvg_handle_new_with_flags()
, and then using
rsvg_handle_write()
and 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 rsvg_handle_set_dpi()
or
rsvg_handle_set_dpi_x_y()
on an RsvgHandle
to set the DPI before rendering it.
Rendering
The preferred way to render a whole SVG document is to use
rsvg_handle_render_document()
. Please see its documentation for details.
API ordering
Due to the way the librsvg API evolved over time, an RsvgHandle
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 RsvgHandle
just constructed with rsvg_handle_new()
is not loaded yet, and it does not make sense to call rsvg_handle_render_document()
on it
just at that point.
The documentation for the available methods in RsvgHandle
may mention that a particular
method is only callable on a “fully loaded handle”. This means either:
-
The handle was loaded with
rsvg_handle_write()
andrsvg_handle_close()
, and those functions returned no errors. -
The handle was loaded with
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.
Constructors
rsvg_handle_new
Returns a new rsvg handle. Must be freed with g_object_unref()
. This
handle can be used to load an image.
rsvg_handle_new_from_data
Loads the SVG specified by data
. Note that this function creates an
RsvgHandle
without a base URL, and without any RsvgHandleFlags
. If you
need these, use rsvg_handle_new_from_stream_sync()
instead by creating
a GMemoryInputStream
from your data.
since: 2.14
rsvg_handle_new_from_file
Loads the SVG specified by file_name
. Note that this function, like
rsvg_handle_new()
, does not specify any loading flags for the resulting
handle. If you require the use of RsvgHandleFlags
, use
rsvg_handle_new_from_gfile_sync()
.
since: 2.14
rsvg_handle_new_with_flags
Creates a new RsvgHandle
with flags flags
. After calling this function,
you can feed the resulting handle with SVG data by using
rsvg_handle_read_stream_sync()
.
since: 2.36
Instance methods
rsvg_handle_close
This is used after calling 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 rsvg_handle_write()
to feed data into the handle
;
if you use the other methods like rsvg_handle_new_from_file()
or
rsvg_handle_read_stream_sync()
, then you do not need to call this function.
deprecated: 2.46.
rsvg_handle_get_dimensions
Get the SVG’s size. Do not call from within the size_func callback, because an infinite loop will occur.
deprecated: 2.52. since: 2.14
rsvg_handle_get_dimensions_sub
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.
deprecated: 2.46. since: 2.22
rsvg_handle_get_geometry_for_element
Computes the ink rectangle and logical rectangle of a single SVG element.
since: 2.46
rsvg_handle_get_geometry_for_layer
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.
since: 2.46
rsvg_handle_get_intrinsic_dimensions
In simple terms, queries the width
, height
, and viewBox
attributes in an SVG document.
since: 2.46
rsvg_handle_get_intrinsic_size_in_pixels
Converts an SVG document’s intrinsic dimensions to pixels, and returns the result.
since: 2.52
rsvg_handle_get_pixbuf
Returns the pixbuf loaded by handle
. The pixbuf returned will be reffed, so
the caller of this function must assume that ref.
rsvg_handle_get_pixbuf_sub
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.
since: 2.14
rsvg_handle_get_position_sub
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.
deprecated: 2.46. since: 2.22
rsvg_handle_internal_set_testing
Do not call this function. This is intended for librsvg’s internal test suite only.
rsvg_handle_render_cairo
Draws a loaded SVG handle to a Cairo context. Please try to use
rsvg_handle_render_document()
instead, which allows you to pick the size
at which the document will be rendered.
deprecated: 2.52. since: 2.14
rsvg_handle_render_cairo_sub
Renders a single SVG element in the same place as for a whole SVG document (a “subset”
of the document). Please try to use rsvg_handle_render_layer()
instead, which allows
you to pick the size at which the document with the layer will be rendered.
deprecated: 2.52. since: 2.14
rsvg_handle_render_layer
Renders a single SVG element in the same place as for a whole SVG document.
since: 2.46
rsvg_handle_set_dpi
Sets the DPI at which the handle
will be rendered. Common values are
75, 90, and 300 DPI.
since: 2.8
rsvg_handle_set_dpi_x_y
Sets the DPI at which the handle
will be rendered. Common values are
75, 90, and 300 DPI.
since: 2.8
rsvg_handle_set_size_callback
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:.
deprecated: 2.14.
rsvg_handle_write
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 rsvg_handle_close()
to actually parse the document.
deprecated: 2.46.
Properties
Rsvg.Handle:base-uri
Base URI, to be used to resolve relative references for resources. See the section “Security and locations of referenced files” for details.
Rsvg.Handle:em
Exact width, in pixels, of the rendered SVG before calling the size callback
as specified by rsvg_handle_set_size_callback()
.
deprecated: 2.46.
Rsvg.Handle:ex
Exact height, in pixels, of the rendered SVG before calling the size callback
as specified by rsvg_handle_set_size_callback()
.
deprecated: 2.46.
Rsvg.Handle:height
Height, in pixels, of the rendered SVG after calling the size callback
as specified by rsvg_handle_set_size_callback()
.
deprecated: 2.46.
Rsvg.Handle:width
Width, in pixels, of the rendered SVG after calling the size callback
as specified by rsvg_handle_set_size_callback()
.
deprecated: 2.46.
Signals
Signals inherited from GObject (1)
GObject::notify
The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.
Class structure
struct RsvgHandleClass {
GObjectClass parent;
}
Class structure for RsvgHandle
.
Class members
parent: GObjectClass
Parent class.