Displays the view but confines drawing to a specified region and does not back up to the first opaque ancestor—it simply causes the view and its descendants to execute their drawing code.
A rectangle defining the region of the view to be redrawn; it should be specified in the coordinate system of the view.
Invalidating the View’s Content
Marks the region of the view within the specified rectangle as needing display, increasing the view’s existing invalid region to include it.
var needsDisplay: Bool
A Boolean value that determines whether the view needs to be redrawn before being displayed.
Displays the view and all its subviews if any part of the view has been marked as needing display.
var isOpaque: Bool
A Boolean value indicating whether the view fills its frame rectangle with opaque content.