ios - Quartz 2D Opaque Data Types -

quartz 2d opaque data types

the quartz 2d api defines variety of opaque data types in addition graphics contexts. because api part of core graphics framework, data types , routines operate on them use cg prefix.

quartz 2d creates objects opaque data types application operates on achieve particular drawing output. figure 1-3 shows sorts of results can achieve when apply drawing operations 3 of objects provided quartz 2d. example:

you can rotate , display pdf page creating pdf page object, applying rotation operation graphics context, , asking quartz 2d draw page graphics context.

you can draw pattern creating pattern object, defining shape makes pattern, , setting quartz 2d use pattern paint when draws graphics context.

you can fill area axial or radial shading creating shading object, providing function determines color @ each point in shading, , asking quartz 2d use shading fill color.

i having trouble understanding part of apple reference guide

and things have bold, "them" refereed to?

and please clarify opaque data type , not in c or c++ terms.

thanks in advance, regards.

the phrase opaque type means type contains or references data you're not supposed at, or able at. example, quartz provides cgcontextref type. functions provided creating, obtaining, manipulating, , releasing graphics context using instance of cgcontextref, can't inside cgcontextref , see what's inside. can't reasonably use or change context without using functions provided.