Object positioning

The positioning of an object in TextUserInterfaces.jl means its position and size in the screen. This information is stored in an instance of the structure ObjectPositioningConfiguration. It can be created by the function newopc:

newopc(;kwargs...)

Create an instance of the structure ObjectPositioningConfiguration. The following keywords are available to specify the positioning:

• anchor_bottom: Bottom anchor specification. (Default = _no_anchor)
• anchor_left: Left anchor specification. (Default = _no_anchor)
• anchor_right: Right anchor specification. (Default = _no_anchor)
• anchor_top: Top anchor specification. (Default = _no_anchor)
• anchor_center: Center anchor specification. (Default = _no_anchor)
• anchor_middle: Middle anchor specification. (Default = _no_anchor)
• top: Absolute position of the object top side. (Default = -1)
• left: Absolute position of the object left side. (Default = -1)
• height: Height of the object. (Default = -1)
• width: Width of the object. (Default = -1)

Notice that the position of the object can be defined by relative terms or absolute terms. They can be mixed, but the user must be sure that the system can infer the position and size of the object given the provided set of parameters.

Anchors

Every object has three horizontal anchors and three vertical anchors:

Horizontal anchors
===============================================================================

+-----------------------------------------------------------------------------+
|                                                                             |
| <- Left anchor                 Center anchor                Right anchor -> |
|                                                                             |
+-----------------------------------------------------------------------------+

Vertical anchors
===============================================================================

+--------------------------------- Top anchor --------------------------------+
|                                                                             |
|                                Middle anchor                                |
|                                                                             |
+------------------------------- Bottom anchor -------------------------------+

The positioning information of an object can be informed by attaching those anchors to the anchors of another object. This is accomplished by creating an instance of the structure Anchor:

struct Anchor
    obj::Object
    side::Symbol
    pad::Int
end

to the desired anchor, where obj defines the object we want anchor, side defines which side will be anchored, and pad defines a space.

Thus, suppose that we want that the object B is positioned on the left of object A with the same height and width 9:

                   <-- 9 -->
+-----------------++-------+
|                 ||       |
|                 ||       |
|                 ||       |
|        A        ||   B   |
|                 ||       |
|                 ||       |
|                 ||       |
+-----------------++-------+

Thus, we should create the following ObjectPositioningConfiguration for B:

newopc(anchor_top    = Anchor(A, :top, 0),
       anchor_left   = Anchor(A, :right, 0),
       anchor_bottom = Anchor(A, :bottom, 0),
       width         = 9)

Notice that we attached the anchors top, left, and bottom of B to the anchors top, right, and bottom, respectively, of A. With only this information, the width would be undefined. Thus, we provided this information with the absolute parameter width.