fix: joining paths from different layers with Ctrl+J fails

[Ayush2k02]

screenrecording.graphite.mp4

Fixes #3519

[Keavon]

Hello and thanks for the PR. I need to mention that we do not accept PR descriptions written by AI because they increase the noise-to-signal ratio and usually serve to mislead with obscured inaccuracies. (The same applies to code, which must be written by you.)

[Ayush2k02]

Oh, hey , I had this extension turned on in my IDE https://whatthediff.ai/ , will be mindful to disable it when creating PRs in this repo :) . Also regarding using AI in code, I did use claude code for targeting the files and the fix but did review that intensively before publishing .

[Keavon]

Thanks for the insight into your process (we've been seeing more highly-elaborate-but-not-insightful PR descriptions like this and it's good to know some of the details about what kinds of AI tools are producing them). For code authorship, AI is acceptable for auto-completing lines you would already be typing, but we need contributions to always come from the original thought processes of its human authors who can answer to the reasoning behind each line of changes. Code can't be mysteriously changed without anyone aware of why the change was made. Thanks for working to follow our requirements to building an effective software project.

[0HyperCube]

It doesn't work. I have tried it with some simple lines with a transform.

I guess the vibes haven't fully completed the code.

fail_to_join.graphite

cannot_join_lines_with_transform.mp4

[Ayush2k02]

Taking a look

[Ayush2k02]

After taking a second look at the issue, here is what I came up with: The fix uses index-based tracking to handle PointId remapping:

• Vector::concat() preserves point ordering (layer1 points first, then layer2 points)
• Save each point's index before merge
• Calculate post-merge indices using layer1's point count as offset
• Look up actual PointIds at those indices after merge

Other approaches I considered:

• Position-based matching: Save coordinates, search within 250px tolerance after merge. Fragile—Flatten Path shifts coordinates unpredictably, large tolerance risks wrong matches.
• Hash-based ID prediction: Replicate collision resolution to predict new PointIds. Impractical—hash seed needs internal parameters (current_index, vector_index, node_id) inaccessible from shape_editor.rs.

[Ayush2k02]

Let me know if I am missing something or if there could be any other edge case here

[Ayush2k02]

Screen.Recording.2025-12-28.at.7.12.43.AM.mov

More manual testing with data grid for when the conflicting PointId is not updated so the wrong segment is created , here it is not created .

[0HyperCube]

fail_with_repeat.mp4

However I guess it doesn't matter too much.

[Ayush2k02]

I don't think this for loop is an overhead here, realistically there would'nt be more than 100-200 points max here . Thats just my guess , can definitely have a hashmap here as well

[Ayush2k02]

I have a better solution for this, let me code it up

So basically the issue with the current approach was when layers use the repeat modifier. The merge operation flattens repeated instances, breaking the expected point array structure.

Expected behavior:

• Layer1 has x points
• Layer2 has y points
• After merge: x + y points total

Actual behavior with repeat:

• Layer1 with 2 points × 3 repeat instances = 6 points (not 2)
• Layer2 with 2 points = 2 points
• After merge: 8 points total (not 4)

Since the old approach calculated indices using end_index = end_idx + layer1_count, it assumed layer1_count = 2, but after flattening the repeated instances, layer1 actually contributes 6 points. This causes the lookup to select the wrong points.
Solution

Instead of relying on indices (which change when instances are flattened), we now:

1. Before merge: Store the world-space coordinates of the selected points
2. After merge: Reverse-lookup the PointIDs by searching for those exact coordinates

[Ayush2k02]

screenrecording.graphite.mp4

Some manual testing after the recent commit

[Ayush2k02]

let me know if any other changes are required