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       CHAPTER 10                                                         Document Interchange



10.5.1 Property Lists

       The marked-content operators DP and BDC associate a property list with a
       marked-content element within a content stream. The property list is a dictionary
       containing private information meaningful to the program (application or plug-
       in extension) creating the marked content. It is suggested that programs use the
       dictionary entries in a consistent way; for example, the values associated with a
       given key should always be of the same type (or small set of types).

       If all of the values in a property list dictionary are direct objects, the dictionary
       may be written inline in the content stream as a direct object. If any of the values
       are indirect references to objects outside the content stream, the property list
       dictionary must instead be defined as a named resource in the Properties sub-
       dictionary of the current resource dictionary (see Section 3.7.2, “Resource Dic-
       tionaries”) and referenced by name as the properties operand of the DP or BDC
       operator.


10.5.2 Marked Content and Clipping

       Some PDF path and text objects are defined purely for their effect on the current
       clipping path, without the objects actually being painted on the page. This occurs
       when a path object is defined using the operator sequence W n or W* n (see
       Section 4.4.3, “Clipping Path Operators”) or when a text object is painted in text
       rendering mode 7 (see Section 5.2.5, “Text Rendering Mode”). Such clipped,
       unpainted path or text objects are called clipping objects. When a clipping object
       falls within a marked-content sequence, it is not considered part of the sequence
       unless the entire sequence consists only of clipping objects. In Example 10.2, for
       instance, the marked-content sequence tagged Clip includes the text string
       ( Clip me ) but not the rectangular path that defines the clipping boundary.

       Example 10.2

          /Clip BMC
              100 100 10 10 re W n               % Clipping path
              ( Clip me ) Tj                     % Object to be clipped
          EMC

       Only when a marked-content sequence consists entirely of clipping objects are
       the clipping objects considered part of the sequence. In this case, the sequence is
       known as a marked clipping sequence. Such sequences may be nested. In Example

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