Inconsistent and probably problematic behaviors in coregistration

Describe the bug

Hi, I’ve noticed some inconsistent and probably problematic behaviors in mne coreg. The problems are recorded in the video.

1. The values in MRI Fiducials are not always updated when the user clicks on different positions. For example, the coordinates of nasion are not updated in 00:02-00:09 but that of LPA are updated in 00:12-00:17. Then, the coordinates of RPA are not updated in 00:17-00:20. It’s really frustrating to understand what’s happening…
2. When the values in MRI Fiducials are provided by the user, the coordinate system seems to be inverted. The weird behavior can be viewed from 00:25 to the end of the video.

Because the MRI images were acquired in a fMRI experiment which required the participants to wear goggles and headphones, sometimes I need to use FreeView to find the possible coordinates for better coregistration results. The above problems make it hard to do that.

Nothing was shown on the terminal running mne coreg.

Expected results

Reasonable coregistration.

Actual results

Confusing behaviors in mne coreg.

Additional information

OS: Ubuntu 20.04 mne.sys_info()

Platform:      Linux-5.8.0-40-generic-x86_64-with-glibc2.10
Python:        3.8.5 (default, Sep  4 2020, 07:30:14)  [GCC 7.3.0]
Executable:    /home/ntubabylab/anaconda3/envs/mne/bin/python
CPU:           x86_64: 12 cores
Memory:        62.8 GB

mne:           0.22.0
numpy:         1.19.2 {blas=mkl_rt, lapack=mkl_rt}
scipy:         1.5.2
matplotlib:    3.3.2 {backend=Qt5Agg}

sklearn:       0.23.2
numba:         0.51.2
nibabel:       3.2.0
nilearn:       Not found
dipy:          Not found
cupy:          8.1.0
pandas:        1.1.3
mayavi:        4.7.2
pyvista:       0.26.1 {pyvistaqt=0.2.0, OpenGL 4.5.0 NVIDIA 450.102.04 via GeForce GTX 1660/PCIe/SSE2}
vtk:           9.0.1
PyQt5:         5.15.1

[mmagnuski]

@larsoner I would also expect the nasion coordinates to be updated after each click not only after switching to another fiducial point and then back to nasion.

[yh-luo]

@larsoner it solves the problems and works smoothly, thank you!