spectrum graphics - OpenLibra

Overall then, it would seem
that the text facilities of LSDare
pretty powerful. You can put
text wherever you want it to
the exact pixel — you can print it
any size you want, and in a large
variety of typefaces (twelve in
total!. You can escape from text
mode by pressing CAPS
SHIFT-SPACE or ENTER. You
can re-enter text mode by press
ing key P, or return to BASIC by
jressing SPACE.
The Light Screen Designer
series is now very nearly complete.
The next issue will contain
the penultimate episode, which
will be all about draw ing ellipses.
The final part part eleven —
will doall the colouring in. I know
a lot of people have been waiting
for that facility. After part eleven
there w ill be an Epilogue (I prefer
to call it an Epilogue rather than a
Part Twelve because the program
will be completed in Part
Eleven). This will be just to round
everything off nicely I'll leave
you now to feed in all this
machine code. Bye bye till next
time.
ToniBaker
FWE5T TXLOOP_4 U> c,(F_ruo) Bit 0 of Cs» OVER statu*.
71
LD A,(HL)
07 RLCA Bit 0 of Ai» current pixel fron screen.
11 AND C Bit 0 of A:« O if 0VI® Oj or current
CB19 Jtn c
pixel fiwi screen if OVEP 1.
CB19 RR C Bit 0 of Ce INVERSE status.
A9 ton c If DIVERSE I; then complement
bit 0 of A.
U XOR D Bit O of As: current pixel from
required pixel-layout, with OVER and
INVERSE correctly Implemented.
IP AAA Carry:* pixel to print.
CBlfc HL (HI) Bit 0 of (HL): correctly uteres pixel.
RI POP AF A)t nunfcer of renairing pixels in
5D DEC A
(HL) to consider.
CCFIIU) CALL Z.E^.TJXJLOUR If ell 8 bits of (HL) hsre been deialt
«ith then colour the attribute byte
end point HL to n«t fcyte freei screen.
ri POSH AF Stack acreerv-byte pixel counter.
10E9 0.1*2 TO03PJ Djpllcate pixel >3 nany tinea as
is required.
n FOP AP Ala aereen-byte pixel counter.
Cl POP BC Bt. nunber of tUiea esch pixel mist
10
DEC K
be duplicated.
?0E0 JR KI,TIUX)P_5 Repeat thia proceedur* for all rlxels
rax cp oe
within current pixel-layout row.
2BCC JR Z,TXALLI0H4 Juirp if HL points to a rrw byte.
CB06 TIALLICBJ RLC (HL) This loop re-alligna (HL)
JD DEC A so th.*'. all pixels are back In
aore JH WZ,mLLIOi5 the right place.
CD64EJ CALL £»4,T_C0L0(ffi Colour in the lsat attribute.
EL TIALLIGM POP HL ML; points to fir*t acreen byte
affected in current row.
Dl POP DE DE: points to current row of
pixel-layout.
Cl rop BC Bi- current row nunber.
Ct- coluim number of first pixel
affected in current row.
CDJS00 CALL DD»,DON_P;I hint HL and B one pixel down.
DDCB004S BIT C, (J_PLAGS)
260D JR Z,TIP_J Jupp unless printing in italics.
DDCKXME BIT 1, (J_FLA6S)
2004 JR K2,TIP_? Junp If using full slope.
DECB0066 BIT 4,(J_FUSS) Test OEO/ETO. ROM flag.
C41JDD TTEPJ? CALL K2,K>lJ,LEPT_pnt If reqd, point HL and C one plx left.
ranzD TIP} DEC (BJU6Q)
;>oac JR *Z,TXLOOP_2 Repeat current pixel-layout row
as many tines as Is required.
U DIC DE DE: points to next pixel-layout row.
06 N AF,AF'
JD DEC A
2060 JH BZ.TILOOPJ Repeat proceedure for all rows
C9 SET
of pixel-layout.
ZX CRAPHICS
n
C)
D5
ORO U14
TJ_CTJSTSOR PUSH AP
PUSH BC
PUSH DE
E5 PUSH HL Stack .ill registers.
E5 PUSH HL Stack HL again.
2A905C LD HL, (KA5K_T)
EJ EI (3P),HL Stack nyjtfff enrlables
P_FLAG, HL now restored.
And
£5
PUSH HL
21FPOI u> HL.oirr
22905C LD (KA.;K_T),HL Set DIK flj PAPEJi 8; BRIGHT 8f
El POP HL
FLASH OVES 1 i HVDtSE 0.
11C5EJ Lfl DE,TC_pmL P^int DE to pixel layout for cursor.
CD?lt) CALL EJ91,TJ_PR»r Print the cursor onto the screen.
El POP HI
22905C ID (M*I-j;_r),HL Restore original colours.
El POP HL
Dt POP DE
Cl FOP BC
PI POP AP
C9 RET
5AOJE3
OK S4M
LD A,(WIDTH) '.:- width cf character Or squares).
05 PUSH OE
ID E,A
5F
87
ADD A,A
87 ADD A,A
67 ADD A,A Ai. E-(KIDRH)
DSCB0056 PIT ?,(J_P1A3S)
2801 JR Z,GET_HID_^1 Jitnf unle-- 'is'rg T -Ht tyr*rf'ce.
9) SUB E In which case A:» Te(uiDTH).
Dl aET_wn>_i POP DE
09 RET
ORG F44^
D5 7C_RI0HT PUSH DE
CDJ4E4 C/1L E4M,OE7_WIDTH
5F LD E,A £:• character width Ln pixels.
67 ADD A,A tb twice this width.
61 ADD A,C
J80? JS C,TCR_1 Jump if cursor right no\ possible.
9i SUB I
4F LD C,A C:« new colurtr. r.unfaer of cursor.
D1 TCR_) POP DE
182C JR J_PI*AD0R
D5 ?C_LEF7 tUSH DE
CD34L4 'CALL C454,OET_UIDTt(
5F LD E,A EIw character width in pixels.
79 LD A,C A:» current cursor eolum nunber.
95 SUB E A !• new cursor colum rattier.
D1 POP DE
D6 RET C Return If cursor left not possible.
4F LD C,A C £- new colunn r.u-iber af cursor.
1620 JR J_PUADLfi
D5 TC_D&KN PUSH EC
5A01EJ LD A,(HEIGHT) Ai* character height tn iqur*!,
87 KK A,A
67 ADD A,A
67 ALD A,A
5 T LD E,A E:« character height In nlxel*.
67 ADS A,A 1:» twice this height.
60 ADD A,B
FEBO CP BO
yxe JR *C,TCD_t Jiup if cursor dowr not cceslble.
9) SUB E
47 LO B,A B:» new row number of cursor.
D1 TCD_1 POP DE
180D JR J_FDUDIR
46 ZX COMPUTING DECEMBER/JANUARY 1985