feat: make DRAW to use the screen buffer

Also make cosmetic changes in DRAW3 routine.

Author: boriel

src/arch/zx48k/library-asm/SP/PixelDown.asm

@@ -17,30 +17,41 @@
     push namespace core
 
 SP.PixelDown:
+    PROC
+    LOCAL leave
+
+    push de
+    ld de, (SCREEN_ADDR)
+    or a
+    sbc hl, de
     inc h
     ld a,h
     and $07
-    ret nz
-    ex af, af'  ; Sets carry on F'
-    scf         ; which flags ATTR must be updated
+    jr nz, leave
+    scf         ;  Sets carry on F', which flags ATTR must be updated
     ex af, af'
     ld a,h
     sub $08
     ld h,a
     ld a,l
     add a,$20
     ld l,a
-    ret nc
+    jr nc, leave
     ld a,h
     add a,$08
     ld h,a
-;IF DISP_HIRES
-;   and $18
-;   cp $18
-;ELSE
-    cp $58
-;ENDIF
+    cp $19     ; carry = 0 => Out of screen
+    jr c, leave ; returns if out of screen
     ccf
+    pop de
+    ret
+
+leave:
+    add hl, de ; This always sets Carry = 0
+    pop de
     ret
 
+    ENDP
     pop namespace
+
+#include once <sysvars.asm>

src/arch/zx48k/library-asm/SP/PixelLeft.asm

@@ -20,16 +20,33 @@
     push namespace core
 
 SP.PixelLeft:
+    PROC
+
+    LOCAL leave
+
+    push de
+    ld de, (SCREEN_ADDR)
+    or a
+    sbc hl, de  ; This always sets Carry = 0
+
     rlca    ; Sets new pixel bit 1 to the right
-    ret nc
+    jr nc, leave
     ex af, af' ; Signal in C' we've moved off current ATTR cell
     ld a,l
     dec a
     ld l,a
     cp 32      ; Carry if in screen
     ccf
     ld a, 1
+
+leave:  ; Sets screen offset back again
+    push af
+    add hl, de
+    pop af
+    pop de
     ret
 
+    ENDP
     pop namespace
 
+#include once <sysvars.asm>

src/arch/zx48k/library-asm/SP/PixelRight.asm

@@ -21,16 +21,33 @@
     push namespace core
 
 SP.PixelRight:
+    PROC
+
+    LOCAL leave
+
+    push de
+    ld de, (SCREEN_ADDR)
+    or a
+    sbc hl, de  ; This always sets Carry = 0
+
     rrca    ; Sets new pixel bit 1 to the right
-    ret nc
+    jr nc, leave
     ex af, af' ; Signal in C' we've moved off current ATTR cell
     ld a, l
     inc a
     ld l, a
     cp 32      ; Carry if IN screen
     ccf
     ld a, 80h
+
+leave:  ; Sets screen offset back again
+    push af
+    add hl, de
+    pop af
+    pop de
     ret
 
+    ENDP
     pop namespace
 
+#include once <sysvars.asm>

src/arch/zx48k/library-asm/SP/PixelUp.asm

@@ -16,30 +16,41 @@
     push namespace core
 
 SP.PixelUp:
+    PROC
+
+    LOCAL leave
+
+    push de
+    ld de, (SCREEN_ADDR)
+    or a
+    sbc hl, de
+
     ld a,h
     dec h
     and $07
-    ret nz
-    ex af, af'
-    scf
+    jr nz, leave
+    scf         ; sets C' to 1 (ATTR update needed)
     ex af, af'
     ld a,$08
     add a,h
     ld h,a
     ld a,l
     sub $20
     ld l,a
-    ret nc
+    jr nc, leave
     ld a,h
     sub $08
     ld h,a
-;IF DISP_HIRES
-;   and $18
-;   cp $18
-;   ccf
-;ELSE
-    cp $40
-;ENDIF
+
+leave:
+    push af
+    add hl, de
+    pop af
+    pop de
     ret
 
+    ENDP
+
     pop namespace
+
+#include once <sysvars.asm>

src/arch/zx48k/library-asm/draw.asm

@@ -100,6 +100,7 @@ __DRAW_START:
     LOCAL __PIXEL_ADDR
 __PIXEL_ADDR EQU 22ACh
     call __PIXEL_ADDR
+    res 6, h    ; Starts from 0 offset
 
     ;; Now gets pixel mask in A register
     ld b, a
@@ -112,12 +113,15 @@ __PIXEL_MASK:
     djnz __PIXEL_MASK
 
     ld b, d         ; Restores B' from D'
+    ld de, (SCREEN_ADDR)
+    add hl, de
     pop de			; D'E' = y2, x2
     exx             ; At this point: D'E' = y2,x2 coords
     ; B'C' = y1, y1  coords
+    ; H'L' = Screen Address of pixel
+
     ex af, af'      ; Saves A reg for later
     ; A' = Pixel mask
-    ; H'L' = Screen Address of pixel
 
     ld bc, (COORDS) ; B,C = y1, x1
 

src/arch/zx48k/library-asm/draw3.asm

@@ -11,6 +11,7 @@
 #include once <plot.asm>
 #include once <stackf.asm>
 #include once <draw.asm>
+#include once <sysvars.asm>
 
 ; Ripped from the ZX Spectrum ROM
 
@@ -20,7 +21,6 @@ DRAW3:
     PROC
     LOCAL STACK_TO_BC
     LOCAL STACK_TO_A
-    LOCAL COORDS
     LOCAL L2477
     LOCAL L2420
     LOCAL L2439
@@ -30,7 +30,6 @@ DRAW3:
     LOCAL SUM_C, SUM_B
 
 L2D28   EQU 02D28h
-COORDS  EQU 5C7Dh
 STACK_TO_BC EQU 2307h
 STACK_TO_A  EQU 2314h
 
@@ -262,7 +261,7 @@ L23C1:  CALL    247Dh           ; routine CD-PRMS1
     POP     BC              ; Balance the machine stack
 
     JP      C,L2477         ; forward, if the coordinates of first line
-    ; don't add up to more than 1, to LINE-DRAW
+                            ; don't add up to more than 1, to LINE-DRAW
 
 ;   Continue when the arc will have a discernable shape.
 
@@ -319,7 +318,8 @@ L23C1:  CALL    247Dh           ; routine CD-PRMS1
 ;   the jump will always be made to ARC-START.
 
 ;; DRW-STEPS
-L2420:  DEC     B               ; decrement the arc count (4,8,12,16...).
+L2420:
+    DEC     B               ; decrement the arc count (4,8,12,16...).
 
     ;JR      Z,L245F         ; forward, if zero (not possible), to ARC-END
 
@@ -353,7 +353,8 @@ L2420:  DEC     B               ; decrement the arc count (4,8,12,16...).
 ;   the formula returns the next relative coordinates to use.
 
 ;; ARC-LOOP
-L2425:  RST     28H             ;; FP-CALC
+L2425:
+    RST     28H             ;; FP-CALC
     DEFB    $E1             ;;get-mem-1     rx.
     DEFB    $31             ;;duplicate     rx, rx.
     DEFB    $E3             ;;get-mem-3     cos(a)
@@ -394,7 +395,8 @@ L2425:  RST     28H             ;; FP-CALC
 ;   The mid entry point.
 
 ;; ARC-START
-L2439:  PUSH    BC              ; Preserve the arc counter on the machine stack.
+L2439:
+    PUSH    BC              ; Preserve the arc counter on the machine stack.
 
 ;   Store the absolute ay in temporary variable mem-0 for the moment.
 
@@ -456,15 +458,16 @@ L2439:  PUSH    BC              ; Preserve the arc counter on the machine stack.
 ;   can be deleted to expose the closing coordinates.
 
 ;; ARC-END
-L245F:  RST     28H             ;; FP-CALC      tx, ty, ax, ay.
+L245F:
+    RST     28H             ;; FP-CALC      tx, ty, ax, ay.
     DEFB    $02             ;;delete        tx, ty, ax.
     DEFB    $02             ;;delete        tx, ty.
     DEFB    $01             ;;exchange      ty, tx.
     DEFB    $38             ;;end-calc      ty, tx.
 
 ;   First calculate the relative x coordinate to the end-point.
 
-    LD      A,($5C7D)       ; COORDS-x
+    LD      A,(COORDS)       ; COORDS-x
     CALL    L2D28           ; routine STACK-A
 
     RST     28H             ;; FP-CALC      ty, tx, coords_x.
@@ -475,7 +478,7 @@ L245F:  RST     28H             ;; FP-CALC      tx, ty, ax, ay.
     DEFB    $01             ;;exchange      rx, ty.
     DEFB    $38             ;;end-calc      rx, ty.
 
-    LD      A,($5C7E)       ; COORDS-y
+    LD      A,(COORDS + 1)       ; COORDS-y
     CALL    L2D28           ; routine STACK-A
 
     RST     28H             ;; FP-CALC      rx, ty, coords_y

src/arch/zxnext/library-asm/SP/GetScrnAddr.asm

@@ -3,9 +3,6 @@
 ; Alvin Albrecht 2002
 ;
 
-;INCLUDE "SPconfig.def"
-;XLIB SPGetScrnAddr
-
 ; Get Screen Address
 ;
 ; Computes the screen address given a valid pixel coordinate.
@@ -17,14 +14,13 @@
 ; exit : de = screen address, b = pixel mask
 ; uses : af, b, de, hl
 
-;IF !DISP_HIRES
-
     push namespace core
+    PROC
+    LOCAL rotloop, norotate
 
 SPGetScrnAddr:
     ld a,h
     and $07
-    or $40
     ld d,a
     ld a,h
     rra
@@ -55,57 +51,12 @@ norotate:
     and $e0
     or l
     ld e,a
+    ld hl, (SCREEN_ADDR)
+    add hl, de
+    ex de, hl
     ret
 
+    ENDP
     pop namespace
 
-
-;ELSE
-;
-;.SPGetScrnAddr
-;   ld b,0
-;   ld d,b
-;   rr l
-;   rl b
-;   srl l
-;   rl b
-;   srl l
-;   rl b
-;   srl l
-;   jr nc, notodd
-;   ld d,$20
-;
-;.notodd
-;   ld a,b
-;  or a
-;   ld a,$80
-;  jr z, norotate
-;
-;.rotloop
-;   rra
-;   djnz rotloop
-
-;.norotate
-;   ld b,a
-;   ld a,h
-;   and $07
-;   or $40
-;   or d
-;   ld d,a
-;   ld a,h
-;   rra
-;   rra
-;   rra
-;   and $18
-;   or d
-;   ld d,a
-;
-;   ld a,h
-;   rla
-;   rla
-;   and $e0
-    ;  or l
-;   ld e,a
-;   ret
-
-;ENDIF
+#include once <sysvars.asm>