@Override
    @Nullable
    public ThreeSide getCurrentSide(@NotNull ThreesideTextDiffViewerEx viewer, @NotNull Editor editor) {
      ThreeSide side = null; // we can't just use getCurrentSide() here, popup can be called on unfocused editor
      if (viewer.getEditor(ThreeSide.LEFT) == editor) side = ThreeSide.LEFT;
      if (viewer.getEditor(ThreeSide.BASE) == editor) side = ThreeSide.BASE;
      if (viewer.getEditor(ThreeSide.RIGHT) == editor) side = ThreeSide.RIGHT;
      return side;
    }
@Override
    @Nullable
    public ThreeSide getCurrentSide(@NotNull ThreesideTextDiffViewerEx viewer, @NotNull Editor editor)