Zhiyi Zhang (@zhiyi) commented about dlls/comctl32/combo.c:
if (lphc->dwStyle & CBS_NOINTEGRALHEIGHT) {
nDroppedHeight -= 1;
nDroppedHeight = min(nItems * nIHeight + COMBO_YBORDERSIZE(), nDroppedHeight - 1);
Shouldn't you consider if the items are visible like in the `else` branch?