DLI Implementation and Reference Guide - Datalogics

8.2 DLI Implementation and Reference Guide
Overview of Content Interface
Concepts and Facilities: Guide to the DL Pager Composition System
The Content Interface contains the bulk of the interface. At this level, you make
marks on paper. Those marks may be on a Page or on a Forms XObject. They may be
text, line drawings, or images. The marks made in a content area may also be used in
a patterned color.
Control Structures
Control of style is maintained in the Adobe PDF Library structures
PDEGraphicState and PDETextState. These structures are created and
modified exactly as if the Adobe PDF Library were used without DLI.
When created, content structures are always associated with a given document. They
may be filled with arbitrarily complex text. After filling, they are associated with a
Page or with a Forms XObject. Association destroys the structure. A single content
element may be associated with a Forms XObject. Any number of elements may be
associated with a Page.
A set of transforms may be associated with a content element to position it within the
Forms XObject or Page. This permits simple definition of text in columns or areas.
Layering of text is straightforward:
• The first mark made is considered to be on the bottom; all following marks are
above it.
• When an Image or a Form is included in a page, it is above all preceding text and
below all following text.
• When multiple content elements are contained in a page, they are layered in the
order they are added to the page.
A content element is represented by the structure DLPDFCONTENT. These structures
are destroyed when associated with a page or form, and pointers to them should not
be used after that time.