Widgets are added using matrix notation. A widget can span several
cells, for instance obj[1:2,2:3] <- widget would place the
widget in the first and second rows and second and third columns. The
matrix notation is to specify the space allocated to the widget.
For gWidgetstcltk, it is necessary for a child widget to have the
layout object as its parent container and to call the [<-
method to add the widget. (See the example.)
As a convenience, if the value to be assigned is a character it will
be turned into a glabel object before being added.
Like ggroup, the extra argument expand can be used to
force the widget to expand to fill all the space allocated to it.
Like ggroup, the extra argument anchor can by used to
anchor the child within the space allocated when this space islarger
than needed by the widget. This is specified as a pair of values from
-1,0,1 to indicating the x and y positioning of the widget within the
cell.
Like ggroup, the extra argument fill can by used when expand is given, but not anchor, to have the widget expand in the x direction, the y direction, or both (the default). (Toolkit specific).
The method [ can be used to subset. In the simplest usage, it
returns the item at index i,j. (The item at i,j may be in other
cells too. The return value is a gwidget if 1x1, a list if 1xn or
mx1 (n>1), or a mxn matrix of items.