The Fl_Tile class lets you resize the children by dragging the border between them:
Fl_Tile allows objects to be resized to zero dimensions. To prevent this you can use the resizable() to limit where corners can be dragged to.
Even though objects can be resized to zero sizes, they must initially have non-zero sizes so the Fl_Tile can figure out their layout. If desired, call position() after creating the children but before displaying the window to set the borders where you want.
The "borders" are part of the children, an Fl_Tile does not draw any graphics of it's own. In the above example all the final children have FL_DOWN_BOX types, and the "ridges" you see are two adjacent FL_DOWN_BOX's drawn next to each other.
Creates a new Fl_Tile widget using the given position, size, and label string. The default boxtype is FL_NO_BOX.
The destructor also deletes all the children. This allows a whole tree to be deleted at once, without having to keep a pointer to all the children in the user code. A kludge has been done so the Fl_Tile and all of it's children can be automatic (local) variables, but you must declare the Fl_Tile first, so that it is destroyed last.
Drag the intersection at from_x,from_y to to_x,to_y. This redraws all the necessary children.
The "resizable" child widget (which should be invisible) limits where the border can be dragged to. If you don't set it, it will be possible to drag the borders right to the edge, and thus resize objects on the edge to zero width or height. The resizable() widget is not resized by dragging any borders.