I use media queries in my extension to make it responsive and it works, it response well when i resize windows. But there is a visualization area for every visualization object and i can't get the width and height of it, so i can't make it more responsive. You can see the visualization area which is in a yellow square in below picture, i looked the api but can't find anything. Any help will be useful, thanks.
Hmm media queries seems way overkill for your extension.
Your paint method gets called with a $element argument which is a jquery wrapper for your div. The same paint function gets called on every resize event (well almost we throttle it for you) so you can measure your width and height on every paint call and draw your viz differently depending on the values.