Incorrect drag after adding pane programatically

[dadebue]

Describe the bug

Dragging a PaneResizer after inserting an pane programatically leads to incorrect size changes when the pane was added with splice or unshift. When pushing a pane to the array everything is fine.

Or am I using something wrong?

Screenshot_2024-06-04_15-05-18.mp4

Reproduction

• create layout with multiple groups
• add a pane programatically with splice or unshift

REPL: https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAE8VVUY-bRhD-K5NNJePIwNnyS4lxW7VSdQ-RoubxuAfMDrD1sot2F99dKP-92l3A-JIoeWpt2WZnmO-b-ZgZ96RkHDVJHnoi8gZJQn5rW7Ih5qW1B31BbpBsiJadKqzloAvFWgM8F1WaEaMzcswEAGtaqQz08DEX-KeSXbtxl_77L9TsMyoYoFSygVWbCyylqnD1PhOZGYPn0N9l00qBwoy3R_HsinxKLk5kBmyi8OHF-iGF3tmA0QS0UUxU772BMoWFYVIksKqlYp-lMDlfwT-wuqAyrPCHTlAsmUA6htk0dTLCPzw66zAyF1JoAxWaewopBGtIj_AhN3VUcilV4C5VLqhsgjW8g-2dfa0jIz-5xIK1BbEfjgYqW1pyreMnbXKDQW-V9eU4omC98ZZv1DN6x7Qf_AmgXyLAsJntLgX3vqWYrEuaWaeFfyL6guG1AR5n0oneW4b1jZxSFJwV51nQMUMnT-TYHraP_iLSLWcFBtvN3eYVm5N2mPS9Qd7-EHTb6Tr4Bugh9hNwtHkffDcmNeb0mIkDZ-IMCnmaEW1eOOoa0WQEaoVlmpHamFYncdyJ9lxFhWxikzP-xAQttP51F-2i7c8xZdrM9qhhIiq0zkh8dNw3fJk4nDpjpICC51qnGWlMuIeGh3s4SUVRQRtuMwL9WP5wvBcalQFmsIHAS7g-xB7l-MN4I1w64W6H48dO1w52iUbZZYZqw31Gjp8sJRMVBFJBJ3TNSsNEtYaTwvysgaq8qqy_yHnR8dx2H8gSTI1w7XRQfqHoN4eYsouXYkmm0IZeEOqw7DiHJ__TPod7aE_hbj-urcNXds6JCZq4vgAvumcgG9JIykqGlCRGdThs5qU5o_znq9N-_p8daGzudnn1fn3ZtWWly08c7cAk_c1WG6y_VbLVgZ352zGaK79mmfrwaDYMwOhkZHSYH_XtE1bSFkBDXo3q9m8xL2pYzDnkGtoNMPo8-FXk6B26Qz7O-_EtK2GZweQAmAZfIy89dtq3g-uXMTZBrnEZsWzPMdkx9ZLjsxsdHRYoDCr4u9OGlS_T8VrUNIanKqxU_hJu7-5cndNGzoyX8apT1NtCE7j_A3x515unzh4zjlk5CeL-b0ePU4HRZ3iTpksZI46iMjWEsJ3LPCw79otZ_G6dpyo85cW5cvXC6wZI0_Taqb-s6nC3SlZP4W41ZGRWfq6ij-1zdwt77q6vTvHj8C8B_x5CBgkAAA==

Logs

No response

System Info

svelte-5-preview vercel

Severity

annoyance

[huntabyte]

Are you able to reproduce this in Svelte 4?

[dadebue]

Yes: https://svelte.dev/repl/c89d1fc9ebc5415a9e890388f279536e?version=4.2.18

[huntabyte]

Okay here's a workaround at least for the time being: https://svelte.dev/repl/c89d1fc9ebc5415a9e890388f279536e?version=4.2.18

When I find some time I'll try to investigate why it is getting registered backwards like that.

[dadebue]

Did you mean to paste a different link? The link you provided is the REPL I created so I still get the problem 🙈

[huntabyte]

Whoops, here you go REPL

[LePau]

I had the same issue with collapsing a panel using a key block, but that doesn't seem to fix the drag issue in that case. Any ideas?

Just adding here as another data point.

[huntabyte]

I'm unsure how this could be solved by paneforge, as I don't see a way for us to know what pattern you are using on the outside to mutate arrays. Even adding a unique key to the {#each still seems to produce the opposite drag behavior, which leads me to believe something is getting confused.

I'll look into this further when I have the time, if someone else wants to put a second set of eyes it would be appreciated.