Glossary

• backing scale factor  

  The relationship between points in a virtual object (view, window, or screen) and the pixels that represent that object onscreen. In OS X this value is either 1.0 or 2.0, depending on the resolution of the underlying device.



• backing store  

  An offscreen buffer used for drawing operations.



• base space  

  The default coordinate system for a graphics context.



• current transformation matrix  

  An affine transform that the system uses to map points from one coordinate space to another for the current graphics context.



• device space  

  A fixed coordinate system that corresponds to individual pixels on a physical device, such as a display or printer. One unit in device space equals one pixel.



• framework-scaled mode  

  The way the application framework automatically adjusts Cocoa app content onscreen to ensure sharp graphics whether the display is standard or high resolution. Application frameworks draw all standard user interface elements—such as buttons, menus, and the window title bar—to the correct size for the resolution.



• magnified mode  

  An accommodation OS X makes to allow apps that aren’t high resolution to run acceptably on a high-resolution display. The system magnifies the contents of the backing store to fill the display.



• pixel  

  The smallest picture unit on a display device.



• point  

  One unit in user space, prior to any transformations on the space. The term point has its origin in the print industry, which defines 72 points as equal to 1 inch in physical space. When used in reference to high resolution in OS X, points in user space do not have any relation to measurements in the physical world.



• user size  

  The size, in points, of an object onscreen.



• user space  

  A device-independent coordinate system that an application draws into. One unit in user space equals one point. You can transform user space by applying scaling, rotation, and translation. The mapping from user space to device space depends on: (1) The mapping between default user space and device space; (2) The coordinate transformations applied to user space either by the system API or your own API.