Instance Property

canDraw

A Boolean value indicating whether drawing commands will produce any results.

Declaration

@property(readonly) BOOL canDraw;

Discussion

The value of this property is YES when drawing produces expected results. A view object can draw onscreen if it is not hidden, it is attached to a view hierarchy in a window (NSWindow), and the window has a corresponding window device. A view object can also draw during printing if it is a descendant of the view being printed.

Check the value of this property before attempting to force drawing to a specific context. For example, if the value of this property is NO, do not call lockFocus or do issue any drawing commands from the view. You do not need to check whether drawing can occur when calling the display method or any of its related methods. The display methods perform appropriate checks before asking the view to draw itself.

See Also

Drawing

- updateLayer

Updates the view’s content by modifying its underlying layer.

- drawRect:

Overridden by subclasses to draw the view’s image within the specified rectangle.

canDrawConcurrently

A Boolean value indicating whether the view can draw its contents on a background thread.

visibleRect

The portion of the view that is not clipped by its superviews.

- getRectsBeingDrawn:count:

Returns by indirection a list of nonoverlapping rectangles that define the area the view is being asked to draw in drawRect:.

- needsToDrawRect:

Returns a Boolean value indicating whether the specified rectangle intersects any part of the area that the view is being asked to draw.

wantsDefaultClipping

A Boolean value indicating whether AppKit’s default clipping behavior is in effect.

- bitmapImageRepForCachingDisplayInRect:

Returns a bitmap-representation object suitable for caching the specified portion of the view.

- cacheDisplayInRect:toBitmapImageRep:

Draws the specified area of the view, and its descendants, into a provided bitmap-representation object.