+ // NOTE: if getItemAt* are overridden, it may make sense to cache the
+ // start and height of the last item returned by getItemAtPos and fast
+ // track returning their properties for getItemStart and getItemHeight.
+ // The "hot" code path calls getItemAtPos first, then will query
+ // getItemStart and getItemHeight on it soon.
+ // When overriding, the following consistency rules must hold:
+ // getTotalHeight() == SUM(getItemHeight(i), i, 0, me.nItems-1)
+ // getItemStart(i+1) == getItemStart(i) + getItemHeight(i)
+ // for 0 <= i < me.nItems-1
+ // getItemStart(0) == 0
+ // getItemStart(getItemAtPos(p)) <= p
+ // if p >= 0
+ // getItemAtPos(p) == 0
+ // if p < 0
+ // getItemStart(getItemAtPos(p)) + getItemHeight(getItemAtPos(p)) > p
+ // if p < getTotalHeigt()
+ // getItemAtPos(p) == me.nItems - 1
+ // if p >= getTotalHeight()