We seem to already be strictly better than the other browsers. Currently we just zoom to the container of the columns. We could zoom to the specific column tapped on.

This is a follow up to review comments in bug 1701749.

One specific case Emilio mentioned was to look at how a block split over two columns is handled.

The bounding rect of the div split across columns contains the rects from both parts of the div. Then our behaviour depends on the aspect ratio of that rect vs our viewport. If the bounding rect is taller than or viewport in aspect ratio we shrink the height of the rect to match the aspect ratio of the viewport, and then center it around the cursor. The result is that we zoom in on the two columns, but vertical position shows the part of the div that we double tapped on. If the rect is not taller than the viewport in aspect ratio then we zoom to fit the whole rect (ie both parts).

It doesn't sound ideal, but it seems to feel fine actually.