Feature request: undo/redo

[maximbaz]

Feature request: undo/redo

[Gskartwii]

Hey! Thanks for your kind words, I really appreciate it.

Undo and redo are a very good and essential idea. I have already started working on them, though I've got a brick wall because I'm confused by the API of the underlying to byte string rope.

teehee/src/history.rs

Lines 38 to 76 in deafef8

	fn chain(self, after_self: &Rope, next: RopeDelta) -> Action {
	let after_next = after_self.apply_delta(&next);
	let (ins1, del1) = self.delta.factor();
	let (ins2, del2) = next.factor();
	let inserted_first = ins1.inserted_subset();
	let del1_expanded = del1.transform_expand(&inserted_first);
	let inserted_in_mid_text = inserted_first.transform_shrink(&del1_expanded);
	let inserted_second = ins2.inserted_subset();
	let inserted_total = inserted_in_mid_text.transform_union(&inserted_second);
	let del2_expanded = del2.transform_expand(&inserted_second);
	let inserted_in_next_text = inserted_total.transform_shrink(&del2_expanded);
	let tombstones = after_next.without_subset(inserted_in_next_text.complement());
	let ins2_in_final_union = ins2
	.transform_expand(&del1_expanded, true)
	.inserted_subset();
	/*let ins1_in_final_union = ins1
	.transform_shrink(&del1_expanded)
	.transform_expand(&inserted_second, false)
	.inserted_subset();
	let insertions_in_final_union = ins1_in_final_union.union(&ins2_in_final_union);*/
	let insertions_in_final_union = dbg!(ins1
	.transform_shrink(&del1_expanded)
	.transform_expand(dbg!(&inserted_second), false)
	.inserted_subset());
	let deletions_from_final = del2_expanded
	.transform_union(&del1_expanded)
	.transform_expand(&insertions_in_final_union);
	Action {
	delta: RopeDelta::synthesize(
	&tombstones.into_node(),
	dbg!(&insertions_in_final_union),
	dbg!(&deletions_from_final),
	),
	}
	}
	}

The above function is meant to be able to chain together two deltas (for example two byte insertions in Insert mode) into a single delta, so that an Insert mode change can be stored in a memory efficient manner. I'm just not quite able to work out how to construct the delta, though I will be making an effort to work on this between everything else. Feel free to advise me if you have an idea on that!