I have noticed some strange and unusual behavior in SLXEditor_2.9.2 (and also 2.8.9b) when loading (either directly or via NeoLemmix CE 1.0.1) the gaps_V2.nxvl (https://www.lemmingsforums.net/index.php?action=dlattach;attach=23476) level (or gaps.nxlv for that matter) from saba (https://www.lemmingsforums.net/index.php?msg=106338).
With the saba level loaded in the aforementioned editor, if you select, for example, terrain pieces located at 102/191, -5/93, or 324/260 and apply the various ROTATE, INVERT, or FLIP functions to them, we observe that the behavior of these pieces when the chosen function is applied is not at all what is expected and that, in addition, the normal fluidity of general movement of pieces in the editor is significantly reduced.
However, this bug (functions and fluidity) does not exist if you load the gaps_V2.nxlv level in SLXEditor_2.8.8!
Problem with SLXEditor 2.9.2? With this specific level? A combination of both?
This one took a little bit of tracking down, but it originates from the new "Highlight Erased Pieces" feature, which draws eraser pieces with purple solid fill instead of a transparent overwrite.
The issue is that the rendering was checking the setting byte-by-byte, which is horrendously expensive and causes huge slowdown on any level which contains more than about 10 eraser pieces. The level in question here has many eraser pieces, which has helped to flag up this issue.
The fix is to cache the setting once per rendering cycle, and apply the cached setting. This restores the usual speed and fluidity of rendering, even for levels with many pieces.
Fixed in commit cb0c2e6.