If you click on the slots, it works well.
If you drag the scroll bars, the slots may stop at the gap between values, but dragging on the slots are disabled on Firefox and IE.
Using the scroll wheel on mouse does not solve the problem.
Sometimes using the "qx.ui.mobile.control.Picker.setSelectedIndex()", it fails to select the correct item.
This problem does NOT occur on Chrome 43.0 for desktop and mobile version.
And does not occur on Firefox for Android (Version 39.0).
Since this is a problem of mobile widgets on desktop browsers,
I am wondering whether I should consider this as a bug or issue.
Anyway, this is inconvenient for writing the mobile applications on a desktop PC.