Eagerly Prefetch Tiles

[ryan-berger]

Something I've noticed is that we are much too far behind the user when they start dragging with their mouse. I think if we were able to prefetch tiles surrounding the current zoom level, I think this would contribute to less jank, and will have the user

Same might go for searching. We might be able to pre-fetch tiles that correspond to search results so that if a user were to land there, it would be in cache and ready.

[ryan-berger]

To add, it also might be a good idea to start fetching longest line of sight tiles at the mouse-level. As you drag your mouse over it then it fetches the area so that when you click it is already in cache.

[tombh]

So we've decided that this is more of an issue for the first day after a new world run compilation. Therefore that the slowness is mostly caused by the loading of tiles into the CDN from R2.

But I think there is actually still an interesting issue, that might be the opposite of pre-fetching. On slower connections, the fact that in-progress tile downloads aren't cancelled when they exit the viewport, might be slowing things down. Say for example, if you click on a longest line URL and it automatically flies from zoom level 0 to 10, then it tries to load tiles from every single zoom level on the way to its destination. And all of the tiles are loaded to completion whether they are rendered or not!