Font size not applied properly in composite diagram about diagrams-svg

[cchalmers]

On a related issue, certain attributes are being output several times even though they're identical. Here's the gradient example from the tutorial: http://lpaste.net/129623. Each gradient is defined an applied 3 times even though they're identical.

I think if we accumulate the style in the state and only apply the style when it's used, like the other backends, both these issues should be fixed.

[jeffreyrosenbluth]

The reason that the SVG backend doesn't accumulate styles using the state stack is probably a bit of a historical accident. When i switched to an RTree instead of a list of primitives one of the first things i did was to port the svg backend. Hence the RTree based backend probably inherited these redundancies from the list based backend. This was before byorgey designed the state stack to convert the cairo backend. It's probably worth looking into @cchalmers suggestion.