Joining (merging) identical nodes shouldn't shift said nodes location

[rickmastfan67]

Inkscape 0.48.4 r9939
Windows 7 x64

Steps to reproduce:
1. Open attached file.
2. Select the black item that's on your screen.
3. Go into the node editing mode (F2).
4. Use your mouse and draw a box right below the red arrow (the red arrow points to the problem location) to select the two nodes that are in the same location.
5. Go up to the "Join selected nodes" button in the toolbar and click it.

What happens:
The 2 nodes are "merged" together, but are shifted to the left, which changes the item.

What should happen:
The 2 nodes should be merged together, but stay in the same location. Also the the "cusps" that lead to other nodes/lines that are on either side of the original nodes should stay in the same location.

I have to admit, this is really annoying when I'm trying to clean up files that I got from friends for work projects. I don't like having to take a lot of time to manually merge the nodes in stuff like Notepad++ to make sure everything stays the same. The reason is because when I add a stroke (if necessary), it sometimes either has a gap, or sharp spike because of duplicate nodes at the same location that should have been one node to start with.

[su_v (suv-lp)]

Not reproduced with old node tool in Inkscape 0.47 (select both nodes, first break path at selected nodes, then join the selected end nodes).
Reproduced with new node tool in Inkscape 0.48.0, 0.48.4 and current trunk (r12137) on OS X 10.7.4

Workaround with Inkscape 0.48 for the path in the attached example:
1) select both nodes
2) delete segment between the two non-endpoint nodes
3) join the selected nodes

-> resulting path has 13 nodes total, and the outline curve is unchanged.

[su_v (suv-lp)]

Possibly related earlier reports:
- Bug #614628 “"Join selected nodes" adds an extraneous node when joining near-duplicate nodes” (comment #3)
- Bug #515237 “Rotate shape adds node” (comment #12)

[Beluga (buovjaga)]

Still repro.

Arch Linux 64-bit, KDE Plasma 5
Inkscape 0.92pre1 15073 (GTK3)

[jazzynico (jazzynico)]

Reproduced on Windows XP (32-bit), lp:inkscape/0.92.x rev. 15318.

The two cusp nodes have handles with a different length. Merging them creates a symmetric node, but keeps original handles combined length and handles end position. Therefore, as we now have a symmetric node, its position is exactly in the middle of the handles (in the test file, shifted to the left compared to the original nodes position).

[Nathan Lee (nathan.lee)]

Hi - thanks for reporting this bug, as part of the bug migration, I've closed this issue and copied over the information to the Inkscape's new bug tracker on GitLab (it was reported in https://gitlab.com/inkscape/inkscape/-/issues/1763 and can still be tracked there)