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     CHAPTER 5                                                                            Text



       text position is changed after the glyph is painted in writing mode 0; its vertical
       component is always 0.
     • The center diagram illustrates writing mode 1, vertical writing. w1 is the dis-
       placement vector for writing mode 1; its horizontal component is always 0.
     • In the right diagram, v is a position vector defining the position of origin 1 rel-
       ative to origin 0.


                          ur                           Origin 1                     Origin 1




                                                                          v
  Origin                     w0
    0
                                                                      Origin
                                                                        0
       ll               New text                     w1
                        position            New text position

            Writing mode 0                 Writing mode 1              Mode 1 relative to mode 0
             (horizontal)                     (vertical)


                     FIGURE 5.5 Metrics for horizontal and vertical writing modes


     Glyph metric information is also available separately in the form of Adobe font
     metrics (AFM) and Adobe composite font metrics (ACFM) files. These files are
     for use by application programs that generate PDF page descriptions and must
     make formatting decisions based on the widths and other metrics of glyphs. Also
     available in the AFM and ACFM files is kerning information, which allows an
     application generating a PDF file to determine spacing adjustments between
     glyphs depending on context. Specifications for the AFM and ACFM file formats
     are available in Adobe Technical Note #5004, Adobe Font Metrics File Format
     Specification; the files can be obtained from the Adobe Solutions Network Web
     site (see the Bibliography).


5.2 Text State Parameters and Operators

     The text state comprises those graphics state parameters that only affect text.
     There are nine parameters in the text state (see Table 5.1).

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