Re-rendering SVGs from the cache. Recomputed or re

Question

I can't find an answer to this question, when the browser takes an SVG from the cache does it re-compute the xml or not, does it store the 'IMAGE' that it has already created? (How?)

I would've have thought not, but then I've noticed how fast repeated svgs load.

I've also noticed slowness on a page logo (in mobile browsers) which make me think THEY re-compute the SVG, so i've moved to PNG's (which are obviously cached) for mobile to save a lot of computational work for the low end phones.

So maybe, does the answer depend on the browser / browser type / browser settings?

*my svg's are compressed svgz's by the way

Answer 1

Sometimes it does and sometimes it doesn't. Most browsers go to some effort not to rerender things unless they have to. There is a buffered-rendering property in SVG 1.2 Tiny that may help if you're using Opera, other browsers try to do things automatically without requiring such hints though.

Browsers generally don't cache SVG content as a simple bitmap though. They do cache things like the absolute position and size of shapes and text with transforms applied, the css tree structure, gradients etc and then use this information they can redraw the content much more quickly than having to work it out each repaint. Such information allows browsers to copy with javascript and SMIL animation of parts of the SVG content as well as user scrolling.