Resizable split of children
Inherits from Group
The Tile class lets you resize the children by dragging the border between them:
Tile allows objects to be resized to zero dimensions. To prevent this you can use the resizable property to limit where corners can be dragged to.
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.
Even though objects can be resized to zero sizes, they must initially have non-zero sizes so the 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. A Tile does not draw any graphics of its own. In the above example all the final children have Boxtype.down types, and the "ridges" you see are two adjacent Boxtype.downs drawn next to each other.
Drag the intersection at from_x,from_y to to_x,to_y. This redraws all the necessary children.