isCellNavigable is ignored when holding shift

[maejoh]

I'm simulating merged cells with colspan and rowspan. I added cells with the 'display: none' style in places where the cell was really covered by an elongated cell, and made a function for isCellNavigable that considers such hidden cells as not navigable. This slightly improves keyboard navigation around the spreadsheet, though it isn't perfect. However, when selecting multiple cells by holding down the shift key, the hidden cells are being included.

For example, if I have cell B selected and press the right arrow key, cell G becomes selected (cell D and E are technically in the row above, so there are two filler cells in between B and G to make columns align for vertical navigation; they're set as non-navigable, so they're skipped when using keyboard movement).

But if I select cell B, and hold shift, I have to hit the right arrow key twice to select cell G. This wouldn't be a problem if that were because it was selecting cell D and E in between (which would be the best outcome), but since those don't appear to be selected, I can only assume the extra required keystrokes are due to the hidden cells being navigated to.

I believe this is a bug with keyboard navigation not taking isCellNavigable into account when the shift key is held for multi-cell selection.