A Layer is a rectangular region of grid cells. A layer has methods to access its columns, rows, width and height. A layer can be stacked on top of another layer in order to expose a transformed view of its underlying layer's grid cell structure.
Columns and rows in a layer are referenced either by position or index. The position of a column/row in a layer corresponds to the physical location of the column/row in the layer. The index of a column/row in a layer corresponds to the location of the column/row in the lowest level layer in the layer stack. These concepts are illustrated by the following example:
Hide Layer C 0 1 2 3 4 <- column positions 1 0 3 4 5 <- column indexes Reorder Layer B 0 1 2 3 4 5 <- column positions 2 1 0 3 4 5 <- column indexes Data Layer A 0 1 2 3 4 5 <- column positions 0 1 2 3 4 5 <- column indexes
In the above example, Hide Layer C is stacked on top of Reorder Layer B, which is in turn stacked on top of Data Layer A. The positions in Data Layer A are the same as its indexes, because it is the lowest level layer in the stack. Reorder Layer B reorders column 0 of its underlying layer (Data Layer A) after column 2 of its underlying layer. Hide Layer C hides the first column of its underlying layer (Reorder Layer B).
Layers can also be laterally composed into larger layers. For instance, the standard grid layer is composed of a body layer, column header layer, row header layer, and corner layer:
corner | column header |
row header | body |
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