Specifies whether the window is to optimize focusing and drawing when displaying its views.
If YES, the window will optimize focusing and drawing for its views; if NO, it will not, in which case, the window does not preserve the Z-ordering of overlapping views when an object explicitly sends lockFocus to a view and draws directly to it, instead of using the AppKit standard display mechanism.
The optimizations may prevent sibling subviews from being displayed in the correct order—which matters only if the subviews overlap. You should always set flag to YES when there are no overlapping subviews within the window. The default is NO.
Passes a displayIfNeeded message down the window’s view hierarchy, thus redrawing all views that need to be displayed, including the frame view that draws the border, title bar, and other peripheral elements.