SECTION 5.3
407
Text Objects
At the beginning of a text object,
T
m
is the identity matrix; therefore, the origin of
text space is initially the same as that of user space. The
text-positioning operators,
described in Table 5.5, alter
T
m
and thereby control the placement of glyphs that
are subsequently painted. Also, the
text-showing operators,
described in Table 5.6
in the next section, update
T
m
(by altering its
e
and
f
translation components) to
take into account the horizontal or vertical displacement of each glyph painted as
well as any character or word-spacing parameters in the text state.
Additionally, a text object keeps track of a text line matrix,
T
lm
, which captures
the value of
T
m
at the beginning of a line of text. This is convenient for aligning
evenly spaced lines of text. The text-positioning and text-showing operators read
and set
T
lm
on specific occasions mentioned in Tables 5.5 and 5.6.
Note:
The text-positioning operators can appear only within text objects.
5.3.2 Text-Showing Operators
The
text-showing operators
space as they do so. All of the operators interpret the text string and apply the text
state parameters as described below.
TABLE 5.6 Text-showing operators
OPERANDS
OPERATOR
DESCRIPTION
string
string
Tj
'
Show a text string.
Move to the next line and show a text string. This operator has the same effect as
the code
T*
string
Tj
a
w
a
c
string
"
Move to the next line and show a text string, using
a
w
as the word spacing and
a
c
as the character spacing (setting the corresponding parameters in the text state).
a
w
and
a
c
are numbers expressed in unscaled text space units. This operator has
the same effect as the following code:
a
w
Tw
a
c
Tc
string
'