If a MultiColumnList receives 2 columsn both of relative size 0.5f they seem to overlap with the area they are assigned to. This leads to a horizontalscrollbar being added for 0.5f 0.5f sizes. Additionally a scrollbar is added earlier than they would visually overlap the given area, so even very close to total rel_dim of 1.f sizes give a scrollbar. The relative sizes don't seem to go along with the the actually given area, instead it seems not to consider margins (given by widget imagery i guess) and scrollbars correctly.
Steps to reproduce: 1. Created MCL widget 2. add two columns each 0.5f relative horizontal dimension