Zooming in can cause misplaced pixels (div tags in wrong order)

[macauleydev]

Steps to reproduce

1. Reload page
2. Type = 7x to zoom in to 9x9 canvas
3. Draw to bottom by scrolling down
4. Draw to bottom-right corner by holding Shift while scrolling down
5. Type = 2x to zoom in to 7x7 canvas
6. Type - 2x to zoom out to 9x9 canvas

Expected result

The drawing should resemble a right triangle, with its 1 inside pixel undrawn.

Actual result

The 1 "inside" pixel appears swapped with the pixel below. Inspection of the div elements shows the reason: The last two children under <div class="column" data-longitude="1"> are in the wrong order.