Handle.renderCairoSub

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.Handle.renderLayer instead, which allows you to pick the size at which the document with the layer will be rendered.

This is equivalent to rsvg.handle.Handle.renderCairo, but it renders only a single element and its children, as if they composed an individual layer in the SVG.

Historically this function has picked a size for the whole document by itself, based on the following rules:

• If the SVG document has both width and height attributes with physical units (px, in, cm, mm, pt, pc) or font-based units (em, ex), the function computes the size directly based on the dots-per-inch (DPI) you have configured with rsvg.handle.Handle.setDpi. This is the same approach as rsvg.handle.Handle.getIntrinsicSizeInPixels.
• Otherwise, if there is a viewBox attribute and both width and height are set to 100% (or if they don't exist at all and thus default to 100%), the function uses the width and height of the viewBox as a pixel size. This produces a rendered document with the correct aspect ratio.
• Otherwise, this function computes the extents of every graphical object in the SVG document to find the total extents. This is moderately expensive, but no more expensive than rendering the whole document, for example.
• This function cannot deal with percentage-based units for width and height because there is no viewport against which they could be resolved; that is why it will compute the extents of objects in that case. This is why we recommend that you use rsvg.handle.Handle.renderLayer instead, which takes in a viewport and follows the sizing policy from the web platform.

Drawing will occur with respect to the cr's current transformation: for example, if the cr has a rotated current transformation matrix, the whole SVG will be rotated in the rendered version.

This function depends on the rsvg.handle.Handle's DPI to compute dimensions in pixels, so you should call rsvg.handle.Handle.setDpi beforehand.

Note that cr must be a Cairo context that is not in an error state, that is, [cairo.context.Context.status] must return cairo.types.Status.Success for it. Cairo can set a context to be in an error state in various situations, for example, if it was passed an invalid matrix or if it was created for an invalid surface.

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.