- macOS 10.10+
NSMatrix uses flipped coordinates by default. The cells in an
NSMatrix object are numbered by row and column, each starting with 0; for example, the top left
NSCell would be at (0, 0), and the
NSCell that’s second down and third across would be at (1, 2).
NSMatrix class has the notion of a single selected cell, which is the cell that was most recently clicked or that was so designated by a
selectCell(withTag:) message. The selected cell is the cell chosen for action messages except for
NSCell), which is assigned to the key cell. (The key cell is generally identical to the selected cell, but can be given click focus while leaving the selected cell unchanged.) If the user has selected multiple cells, the selected cell is the one lowest and furthest to the right in the matrix of cells.