Rsvg.Handle.render_layer

### Method

# Rsvg Handlerender_layer

since: 2.46

#### Declaration [src]

    gboolean
    rsvg_handle_render_layer (
      RsvgHandle* handle,
      cairo_t* cr,
      const char* id,
      const RsvgRectangle* viewport,
      GError** error
    )

#### Description [src]

Renders a single SVG element in the same place as for a whole SVG document.

The `viewport` gives the position and size at which the whole SVG document would be rendered. The document is scaled proportionally to fit into this viewport; hence the individual layer may be smaller than this.

This is equivalent to `rsvg_handle_render_document()`, but it renders only a single element and its children, as if they composed an individual layer in the SVG. The element is rendered with the same transformation matrix as it has within the whole SVG document. Applications can use this to re-render a single element and repaint it on top of a previously-rendered document, for example.

Element IDs should look like an URL fragment identifier; for example, pass `#foo` (hash `foo`) to get the geometry of the element that has an `id="foo"` attribute.

You can pass `NULL` for the `id` if you want to render all the elements in the SVG, i.e. to render everything from the root element.

Available since: 2.46

#### Parameters

`cr`

  Type: `cairo_t`

  A Cairo context.

  The data is owned by the caller of the method.

`id`

  Type: `const char*`

  An element’s id within the SVG, starting with “#” (a single hash character), for example, `#layer1`. This notation corresponds to a URL’s fragment ID. Alternatively, pass `NULL` to render the whole SVG document tree.

  The argument can be `NULL`.
  The data is owned by the caller of the method.
  The value is a NUL terminated UTF-8 string.

`viewport`

  Type: `RsvgRectangle`

  Viewport size at which the whole SVG would be fitted.

  The data is owned by the caller of the method.

`error`

  Type: `GError **`

  The return location for a recoverable error.

  The argument can be `NULL`.
  If the return location is not `NULL`, then you must initialize it to a `NULL` `GError*`.
  The argument will be left initialized to `NULL` by the method if there are no errors.
  In case of error, the argument will be set to a newly allocated `GError`; the caller will take ownership of the data, and be responsible for freeing it.

#### Return value

Type: `gboolean`

`TRUE` on success, `FALSE` on error. Errors are returned in the `error` argument.

API ordering: This function must be called on a fully-loaded `handle`. See the section “API ordering” for details.

Panics: this function will panic if the `handle` is not fully-loaded.