Grid coordinates are zero-based with the upper left (or upper right cell depending on locale) having coordinates (0,0).
If a cell is empty a UI Automation provider must still be returned in order to support the ContainingGrid property for that cell. This is possible when the layout of child elements in the grid is similar to a ragged array.
Example of a Grid Control with Empty Coordinates
Hidden rows and columns, depending on the provider implementation, can be loaded in the UI Automation tree and will therefore be reflected in the RowCount and ColumnCount properties. If the hidden rows and columns have not yet been loaded they should not be counted.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)