Basic Layouts Example - Reducing the size of the window modifies the layout

Description:

Reducing the size of the window modifies somewhat the layout of the window. The text box taking 2/3 is reduced, so that it does not take anymore the supposed size.
Steps to reproduce:

1. Open the Basic Layout Example
2. Reduce the size of the window until the 2/3 text box takes less than that.

Expected behavior:

There should be a minimum window size as to make sure that the proportions are kept intact when resizing the window.
Observed behavior:

The proportions can changed as there are no minimum window size.

Special rules: