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