Support measuring items automatically

[juangl]

Hello, everyone!

I'd like to implement this feature, unfortunately, I'm not pretty sure how to do that. What would be the implications of not using getItemLayout with the actual code?

[janicduplessis]

Right now we need the layout of each cell to be able to know in which column to put them in (always the column with the smallest total height). To be able to do the measuring I think the best way to go is check how it is implemented in VirtualizedList and do something similar.

I think what might make it hard is that we don't want to measure all rows at once, only those that will be visible so this means we need to also know what is the state of windowing. I wonder if at this point it would just be simpler to fork the VirtualizedList code and adapt it to support this layout.

So yeah at this point I'm really unsure of what the proper solution is :), we'd just have to try some stuff to see if it works.

[juangl]

@janicduplessis sounds interesting.

It's worth to take a look at the source code of FlatList since numColumns is implemented in FlatList.

[kaifaust]

@juangl Can we compromise and measure each cell in one swoop, then pass explicit dimensions to each item?

[janicduplessis]

@kaifaust We could do that until we have a better implementation but we have to make it sure it is clear that not providing the getItemLayout will cause all items to be measured so it should only be used with small data sets.