Constraint

The Constraint property allows you to specify the number of rows or columns the grid will have. There are three options, as shown:

The Fixed Column Count and Fixed Row Count allow you to specify an amount of columns or rows, respectively. If you select either of these options, a new property, Constraint Count, will become available. You then specify how may columns or rows you want. When you select Fixed Column Count, the number of rows will be variable. When you select Fixed Row Count, the number of columns will be variable.

The Flexible option automatically calculates the amount of rows and columns for you based on the Cell Size and the Start Axis chosen. It will begin laying out the children in the defined pattern until there is no space left on the chosen axis. It will then continue on. Whichever axis is specified in the Start Axis will have a fixed amount of children, and the other axis will be variable. So, for example, if the Start Axis is set to Horizontal and three children can fit horizontally within the defined space, there will be three columns and the amount of rows will be determined by how many total children there are.