Study: Delayed editor content rendering

[mkoskim]

After improvements in folded container rendering, the usual user cases are handled well. The editor can handle very large documents, assuming that enough of the containers are folded. This is the usual case, because when you are writing, you want to concentrate on certain parts.

If you load a large, unfolded document, or if you press "unfold all" for large document, rendering unfolded document takes time. For these cases, we might consider implementing a feature that unfolds the document in several chunks.