SVG on graphicsview

A lot of people has been asking for a simple way of rendering SVG files on top of qgraphicsview. The only catch was that most of them wanted it along a way of doing selective rendering of SVG files. For example people create huge SVG files and use them as collection of items. Individual elements are nested inside a group element that has a predefined xml:id. I've spent most of yesterday just fixing things in QtSvg to make it possible. The thing that makes it tricky is the following: lets say that we have a SVG fragment with the following structure:
<g transform="scale(0.5,0.5)">
  <g id="myElem" transform="scale(2,2)">
    <rect x="0" y="0" width="2" height="2"       transform="translate(20,20)" />
  </g>
</g>
So we have a group that defines a transformation matrix and inside that group we have our predefined element with id="myElem". The question is what is the bounding box of our rectangle and how do we make sure it fills out the complete area of the rendering viewport. To do that we need to find the rendered element and traverse starting from that element down through its children propagating the transformation matrix correctly. So when we're in rect out transformation matrix is defined by the rect transformation (one translating by 20 in each direction) matrix muliplied by the parent transformation matrix (scaling by 2 in each direction). So the actual bounding box of the rectangle is x=40, y=40, width=4, height=4. Having that all we need to do is set our window to those dimensions and render the element. The code to traverse the SVG tree and QGraphicsSvgItem are already in Qt so once we'll update the snapshots you'll have it.

One of the things that are possible with it is for example having an entire card deck in an SVG file and putting individual cards into predefined groups. I wrote a quick example that takes such constructed SVG files, fetches the cards from the SVG and renders them with some arbitrary transformations on QGraphicsView. A pretty nice feature of it is that I made sure the SVG file has to be loaded only once. QGraphicsSvgItem's can share the context and are capable of picking the right parts of the SVG that actually constitute their whole visual appearance. Thanks to that no unecessary parsing or processing of the SVG tree takes place. A screenshot follows :)

So now it's possible to use QGraphicsView along SVG elements. And since QGraphicsItem's handle all input events one can do pretty nice things by using SVG to define look of the items and handle the logic in the code.