What are some generally accepted practices for navigating between irregularly placed and sized elements in a canvas (such as controls on a form) using the arrow keys?
For example, if the currently focused element is a tall element (A) whose height encompasses three shorter elements to the right of it (B, C and D):
####### #######
# # # B #
# # #######
# #
# # #######
# A # # C #
# # #######
# #
# # #######
# # # D #
####### #######
Which of these elements should be focused when the user presses the Right arrow? The top element (B)? The one in the center (C)?
What if D was focused before the use user moved focus to A by pressing Left? Should focus return to D when the user subsequently presses Right?
I'm wondering if there are some published guidelines for these scenarios.
I haven't looked into any specific guidelines or anything, but it seems that in the first case, when you're on A and you push Right, it should go to B.
If you're already on C or D when you push A, it probably makes sense to go back to that one. I'm less sure about this one, because the user might have gone to A from the bottom as a "shortcut" to get to B (This makes sense if there are a lot of elements in the right column, so instead of going (Up-Up-Up-Up-Up-Up you go Left-Right).