Comment 2 for bug 1560458

The same rules are followed by RowLayout, ColumnLayout and all the other Layout elements.

See https://github.com/qtproject/qtdeclarative/blob/5.7/src/imports/layouts/qquicklayout.cpp#L735

In the code linked above, shouldIgnoreItem() is a function that returns true if the item is not visible or its effective size is 0.

NOTE: shouldIgnoreItem() ignores the item if both width AND height are 0.