NSBox
A stylized rectangular box with an optional title.
Declaration
class NSBoxOverview
Use box objects to visually group the contents of your window. For example, you might use boxes to group related views. Use an NSBox object to configure the appearance of the box.
Subclassing Notes
An NSBox object is a view that draws a line around its rectangular bounds and that displays a title on or near the line (or might display neither line nor title). You can adjust the style of the line (bezel, grooved, or plain) as well as the placement and font of the title. An NSBox also has a content view to which other views can be added; it thus offers a way for an application to group related views. You could create a custom subclass of NSBox that alters or augments its appearance or that modifies its grouping behavior. For example, you might add color to the lines or background, add a new line style, or have the views in the group automatically snap to an invisible grid when added.
Methods to Override
You must override the draw(_:) method (inherited from NSView) if you want to customize the appearance of your NSBox objects. Depending on the visual effect you’re trying to achieve, you may have to invoke super‘s implementation first. For example, if you are compositing a small image in a corner of the box, you would invoke the superclass implementation first. If you’re adding a new style of line, you would provide a way to store a request for this line type (such as a boolean instance variable and related accessor methods). Then, in draw(_:), if a request for this line type exists, you would draw the entire view yourself (that is, without calling super). Otherwise, you would invoke the superclass implementation.
If you wish to change grouping behavior or other behavioral characteristics of the NSBox class, consider overriding contentView, sizeToFit(), or addSubview(_:) (inherited from NSView).
Special Considerations
If you are drawing the custom NSBox entirely by yourself, and you want it to look exactly like the superclass object (except for your changes), it may take some effort and time to get the details right.