Topic       : The GFA-Basic Compendium
Author      : GFA Systemtechnik GmbH
Version     : GFABasic.HYP v2.98 (12/31/2023)
Subject     : Documentation/Programming
Nodes       : 899
Index Size  : 28056
HCP-Version : 3
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Document not found
@help       : Help
@options    : +g -i -s +z
@width      : 75
@hostname   : STRNGSRV
@hostname   : CAB     
@hostname   : HIGHWIRE
@hostname   : THING   
View Ref-FileHLINE x1,y,x2,f,m,addr,num_pattern

x1, y, x2, f, m, addr, num_pattern: iexp

HLINE is similar to the ALINE command, but only horizontal lines can be drawn.
x1 and x2 contain the x-coordinates of the line end points, and y the common
y-coordinate. The expression f contains the color which, depending on the
current screen resolution, takes values from 0 to 15. The parameter m
determines the graphics mode as with ALINE.

addr is the address of a block of memory which contains bit information for
several line styles (each 16 bits). Which style is used for a given line
depends on both the y-coordinate and the parameter num_pattern. They are ANDed
together and the resulting number used as an index to the style table. Thus
num_pattern should generally be one smaller than the power of two (0, 1, 3, 7,
15, etc.), giving the effect that, with num_pattern=7, the first eight styles
will be used sequentially as the y-coordinate moves down the screen. If
num_pattern=3, one of the first four styles will be used, depending on the
y-coordinate.

Example:

    ACLIP 1,0,0,639,399
    '
    pattern%=&X11111111111111111010101010101010
    x%=V:pattern%
    '
    FOR i%=0 to 199
      HLINE 0,i%,639,1,0,x%,1
    NEXT i%

--> Two 16-bit line patterns are put into the variable pattern%. The last
    parameter is 1 (implying 2 possible styles). The lines drawn then use the
    two 16-bit line patterns in pattern% alternately.

Memo: Internally Line-A offset MFILL is set to FALSE.
      Thus only single plane patterns can be used.

Line-A Horizontal Line+