Done all the above.

The right click select is not working
i tried chanege

ED_mball_select_pick

like

EDBM_select_pick, ED_armature_edit_select_pick, ED_lattice_select_pick, ED_curve_editfont_select_pick

but i failed.

Also the following functions uses old code.

hide_metaelems_exec
reveal_metaelems_exec

@Nick Milios (semaphore)

The patches overall are fine, but we need to skip the for loop when there is no selected elements. There is no equivalent of totvertsel/edge/face in metaballs. You need to add this (as its own patch), so we can proceed with the other patches? It should be straight forward.

The right click select may be a different issue, but let's focus on the other operators first?

@Dalai Felinto (dfelinto)

In MetaBall there is a double list mb->editelems of nodes type MetaElem and foreach of them a bitmask flag for ml->flag in first bit to check if it is selected..

To be clear...

Do you want me to edit struct MetaBall and add an int totelemsel?
Find all references functions that changes totvertsel and change all respective functions on mball to change the new totelemsel accordingly?
Then submit it as a pach and then re submit all aabove paches to check it?

@Nick Milios (semaphore) that's what I meant yes, but Campbell just implemented BKE_mball_is_any_selected and BKE_mball_is_any_unselected, so you are good to update them (not re-submit as new patches, but update the existent ones).

I made a differential two weeks ago for MBALL_OT_select_all, but just realized that it didn't get linked back to the parent task, so if it's still current, there it is: D3347 .

hmm... I mentioned the wrong task, that's why.