+ // for interactive resizing. have to move half an increment in each
+ // direction.
+ int mw = w % _size_inc.x(); // how far we are towards the next size inc
+ int mh = h % _size_inc.y();
+ int aw = _size_inc.x() / 2; // amount to add
+ int ah = _size_inc.y() / 2;
+ // don't let us move into a new size increment
+ if (mw + aw >= _size_inc.x()) aw = _size_inc.x() - mw - 1;
+ if (mh + ah >= _size_inc.y()) ah = _size_inc.y() - mh - 1;
+ w += aw;
+ h += ah;
+