Line A Routines
Table 7-11. The Primary Line A Variables That Influence Text
Printing (continued)
Variable
Name
Offset
Description
SKEWMASK
$5E
Mask used to italicize (usually $5555)
WEIGHT $60
Width by which to thicken text for boldface
ROFF
$62 Offset above baseline for italicizing
LOFF $64
Offset below baseline for italicizing
SCALE $66
Scaling flag (0 = no scaling)
CHUP
$68
Character rotation (0 = no rotation,
900 = 90 degree rotation, and so on)
TEXTFG
$6A Text foreground color
SCRTCHP $6C
Pointer to first of two contiguous special
effects buffers
SCRPT2 $70
Offset from SCRTCHP to beginning of
second special effects buffer
TEXTBG
$72 Text background color
The information you must pass to TextBlt can be broken
down into four general categories:
• Information about the font used to print the character (loca
tion, size, and so on)
• Information about the character to be printed (which char
acter, at what position, what color, and so on)
• Information about special effects
• Information about text scaling
The first thing needed to print text character is the ad
dress of a VDI-style text font. If you wish to use one of the
system fonts, get this information from the line A Initializa
tion call. As stated before, this call returns the address of a
pointer table. This table consists of pointers to the font head
ers for the system fonts.
Currently, there are three system fonts on the ST. The
first entry in the header table is the address of the 6 x 6 sys
tem font header, followed by the address of the headers for
the 8 x 8 system font and the 8 x 16 system font.
The font header is an 87-byte data block of information
about the font. Much of the information which must be
placed in the line A variables for TextBlt may be derived
from the font header. For example, the address of the font's
character image data block must be placed in the line A vari
able FBASE.
This address may be found at an offset of 76 bytes from
165
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