The visibility of the horizontal scrollbar should be accounted for when calculating the sizes of items. For instance if the text needs to be elided after resizing the itemview to be smaller in width then it should not be using the original height if this was not the case, it should have a new height as a result.

This is common if the height of the items is influenced by the fact that there are new lines in the text. Once the width is smaller than the length of the first line before the new line it causes it to be elided, but then the positioning of the items is not correct as a result.