Joining paths with the same PointIds doesn't work

[0HyperCube]

To reproduce:

• Draw two lines with the line tool
• Select them both in the layer panel (with shift + click)
• Go to path tool
• Select one point from the first line and one point from the second line
• Attempt to join with Ctrl + J

Logic

The line tool always produces PointId(1) and PointId(2), so when merging the two layers, the point ids of the second line must change to avoid conflict. This causes an issue with the Ctrl+J functionality since it assumes that the PointIds do not change.

PointIds are only guaranteed to be unique within the Vector<Upstream> because same path node must always output the same IDs (since it is a pure function with no input) and you can use the output of the path node several times.

Therefore the Ctrl+J shape_editor.close_selected_path must deal with the fact that the PointIds it holds may change after running merge_layers.

Code for joining layers and adding new segment (currently mistakenly assumes that the PointId will not change after merging):

Graphite/editor/src/messages/tool/common_functionality/shape_editor.rs

Lines 461 to 470 in 9d26c04

	} else {
	// Merge the layers
	merge_layers(document, layer1, layer2, responses);
	// Create segment between the two points
	let segment_id = SegmentId::generate();
	let modification_type = VectorModificationType::InsertSegment {
	id: segment_id,
	points: [end_point, start_point],
	handles: [None, None],
	};

Code that resolves the new ID when there are two conflicting point ids:

Graphite/node-graph/nodes/vector/src/vector_nodes.rs

Lines 1247 to 1251 in 9d26c04

	let mut hasher = DefaultHasher::new();
	(current_index, vector_index, node_id).hash(&mut hasher);
	let collision_hash_seed = hasher.finish();
	output.element.concat(other, transform, collision_hash_seed);

Reproduction video

cannot_join.mp4

[Annonnymmousss]

i have a doubt what if the user is again using cmd+j functionality at the same two points of different layers in which the segment is created will there be another segment between those points or only one segment should be allowed?

[0HyperCube]

@Annonnymmousss Ctrl + J when two points are selected should always add an additional segment, regardless of any other state. This is the currently implemented behaviour.
You can see this functionality when you select two points on the same layer:

join_existing_points.mp4

The only incorrect behaviour is described in detail in the reproduction steps.

[Annonnymmousss]

okay got it, I will look towards this issue.