6.8 Arbitrary line

Name:

»Arbitrary line«

Line-A number:

$A003

Syntax:

See 'Bindings for draw_line'

Description:

This Line-A function draws a straight line from top left to bottom right. The following Line-A variables are used:

Variable

Meaning

X-coordinate of the first end-point

Y-coordinate of the first end-point

X-coordinate of the second end-point

Y-coordinate of the second end-point

fg_bp_1

Bit value of the first plane for the colour that should be used for filling

fg_bp_2

Bit value of the second plane (only low or medium resolution)

fg_bp_3

Bit value of the third plane (only low resolution)

fg_bp_4

Bit value of the fourth plane (only low resolution)

ln_mask

Bit pattern for the line type; the bit pattern is to be interpreted as a dot pattern

wrt_mode

Writing mode; the following modes are possible:

REPLACE 0	Replace
TRANS 1	Transparent (OR)
XOR 2	Inverse (XOR)
INVERS 3	Inverse Transparent (XOR with not(LN_MASK))

lstlin

Is the last pixel of the line to be drawn (1) or not (0)

Note: Independent of the order of the coordinates, the line is drawn always from top left to bottom right.

For a horizontal line there is a faster function $A004 Horizontal line available.

The bindings of TC passes the line mask, writing mode and colour not to the draw_line function, but uses separate functions set_fg_bp, set_ln_mask and set_wrt_mode for setting the parameters in the Line-A parameter block.

Return value:

The function does not return a result. The field ln_mask of the Line-A parameter block is shifted by the output algorithm.

Availability:

All TOS versions.

6.8.1 Bindings for draw_line

Pure-C:

void draw_line(int16_t x1, int16_t y1, int16_t x2, int16_t y2);

Assembler:

; Save registers
movem.l   D0-D2/A0-A2,-(A7)
; Pointer parameter block LINEA
move.l    pParamblk,A0
; First X-coordinate in LINEA.x1
move.w    x1,(38,A0)
; First Y-coordinate in LINEA.y1
move.w    y1,(40,A0)
; Second X-coordinate in LINEA.x2
move.w    x2,(42,A0)
; Second Y-coordinate in LINEA.y2
move.w    y2,(44,A0)
; Bit for first plane in LINEA.fg_bp_1
move.w    colbit0,(24,A0)
; Bit for first plane in LINEA.fg_bp_2
move.w    colbit1,(26,A0)
; Bit for first plane in LINEA.fg_bp_3
move.w    colbit2,(28,A0)
; Bit for first plane in LINEA.fg_bp_4
move.w    colbit3,(30,A0)
; Line style in LINEA.ln_mask
move.w    lnmask,(34,A0)
; Writing mode in LINEA.wrt_mode
move.w    wmode,(36,A0)
; Line style in LINEA.lstlin
move.w    lstlin,(32,A0)
; Line-A opcode
dc.w      $A003
; Restore registers
movem.l   (A7)+,D0-D2/A0-A2

Line-A

Get pixel

Horizontal line