Simplify map scrolling and break it further

inc/dir.inc

@@ -0,0 +1,10 @@
+DEF DIRF_UP EQU (1 << 0)
+DEF DIRF_RIGHT EQU (1 << 1)
+DEF DIRF_DOWN EQU (1 << 2)
+DEF DIRF_LEFT EQU (1 << 3)
+
+RSRESET
+DEF DIRB_UP RB 1
+DEF DIRB_RIGHT RB 1
+DEF DIRB_DOWN RB 1
+DEF DIRB_LEFT RB 1

src/main.s

@@ -1,3 +1,4 @@
+INCLUDE "dir.inc"
 INCLUDE "hardware.inc"
 INCLUDE "util.inc"
 
@@ -98,6 +99,9 @@ scroll_update:
     ld hl, rSCY
     dec [hl]
 
+    ld a, DIRB_UP
+    ld [SCROLL_DIR], a
+
     ld a, [hl]
     and %111
     cp %111
@@ -132,6 +136,9 @@ scroll_update:
     ld hl, rSCY
     inc [hl]
 
+    ld a, DIRB_DOWN
+    ld [SCROLL_DIR], a
+
     ld a, [hl]
     and %111
     jr nz, .update_down_map
@@ -166,6 +173,9 @@ scroll_update:
     ld hl, rSCX
     inc [hl]
 
+    ld a, DIRB_RIGHT
+    ld [SCROLL_DIR], a
+
     ld a, [hl]
     and %111
     jr nz, .update_right_map
@@ -198,6 +208,9 @@ scroll_update:
     ld hl, rSCX
     dec [hl]
 
+    ld a, DIRB_LEFT
+    ld [SCROLL_DIR], a
+
     ld a, [hl]
     and %111
     cp %111

src/map.s

@@ -1,10 +1,10 @@
+INCLUDE "dir.inc"
 INCLUDE "hardware.inc"
 INCLUDE "util.inc"
 
 SECTION "Map Data", WRAM0
 
-PAGEX:: DB ; X coordinate to enqueue map column at
-PAGEY:: DB ; Y coordinate to enqueue map row at
+SCROLL_DIR:: DB
 
 PENDING_ROW_PTR:: DW ; Where to write pending row data (0 = no write)
 PENDING_ROW_DATA:: DS SCRN_VX_B ; Row to be written
@@ -40,10 +40,6 @@ Map_Load::
     ld a, INIT_SCY
     ld [rSCY], a
 
-    ld a, 8
-    ld [PAGEX], a
-    ld [PAGEY], a
-
     ; Store metadata
     ld bc, CURRENT_DATA_START
     ld d, CURRENT_DATA_END - CURRENT_DATA_START
@@ -89,9 +85,9 @@ Map_Load::
 ; Loads the map X-coordinate into B
 MACRO LOAD_MAPX
     ; if SCX <= 0x7f
-    ld a, [rSCX]
-    cp $80
-    jr nc, .wrap\@
+    ; ld a, [rSCX]
+    ; cp $80
+    ; jr nc, .wrap\@
 
     ; B = CAMERA_X - SCX/8
     ld a, [rSCX]
@@ -100,32 +96,32 @@ MACRO LOAD_MAPX
     srln b, 3
     sub b
     ld b, a
-    jr .done\@
+    ; jr .done\@
 
     ; else SCX > 0x7f
-.wrap\@:
-    ; B = CAMERA_X - PAGE_X/8
-    ld a, [PAGEX]
-    ld b, a
-    ld a, [CURRENT_CAMERA_X]
-    srln b, 3
-    sub b
-    ld b, a
-
-    ; HL += PAGE_X/8
-    ld a, [PAGEX]
-    srln a, 3
-    ADD16 hl
-
-.done\@:
+; .wrap\@:
+;     ; B = CAMERA_X - PAGE_X/8
+;     ld a, [PAGEX]
+;     ld b, a
+;     ld a, [CURRENT_CAMERA_X]
+;     srln b, 3
+;     sub b
+;     ld b, a
+
+;     ; HL += PAGE_X/8
+;     ld a, [PAGEX]
+;     srln a, 3
+;     ADD16 hl
+
+; .done\@:
 ENDM
 
 ; Loads the map Y-coordinate into C
 MACRO LOAD_MAPY
     ; if SCY <= 0x7f
-    ld a, [rSCY]
-    cp $80
-    jr nc, .wrap\@
+    ; ld a, [rSCY]
+    ; cp $80
+    ; jr nc, .wrap\@
 
     ; C = CAMERA_Y - SCY/8
     ld a, [rSCY]
@@ -134,151 +130,121 @@ MACRO LOAD_MAPY
     srln c, 3
     sub c
     ld c, a
-    jr .done\@
-
-    ; else SCY > 0x7f
-.wrap\@:
-    ; C = CAMERA_Y - PAGE_Y/8
-    ld a, [PAGEY]
-    ld c, a
-    ld a, [CURRENT_CAMERA_Y]
-    srln c, 3
-    sub c
-    ld c, a
-
-    ; HL += 32 * PAGE_Y/8
-    ld a, [PAGEY]
-    srln a, 3
-    ld d, a
-    ld e, 32
-.adjust_hl\@:
-    ld a, d
-    ADD16 hl
-    dec e
-    jr nz, .adjust_hl\@
-
-.done\@:
+;     jr .done\@
+
+;     ; else SCY > 0x7f
+; .wrap\@:
+;     ; C = CAMERA_Y - SCY/8
+;     ld a, [PAGEY]
+;     ld c, a
+;     ld a, [CURRENT_CAMERA_Y]
+;     srln c, 3
+;     sub c
+;     ld c, a
+
+;     ; HL += 32 * PAGE_Y/8
+;     ld d, 0
+;     ld a, [PAGEY]
+;     ld e, a
+;     REPT 5
+;         SLA16 de
+;     ENDR
+;     add hl, de
+; .done\@:
 ENDM
 
 ; Update map state based on SCX/SCY
 Map_Scroll::
-    ; If SCY = PAGEY, write map row
-    ld hl, PAGEY
+    ; Check scroll up/down
+    ld a, [SCROLL_DIR]
+    and DIRF_UP | DIRF_DOWN
+    jr nz, .scroll_horiz
+
+    ; Check SCY % 8 = 0
     ld a, [rSCY]
-    cp [hl]
-    jr nz, .scroll_down_check
+    and %111
+    ret nz
 
     LOAD_MAPX
 
+    ld a, [SCROLL_DIR]
+    cp DIRB_UP
+    jr nz, .scroll_down
+
     ; C = CAMERA_Y - 2
     ld a, [CURRENT_CAMERA_Y]
     sub 2
     ld c, a
 
-    ; HL = _SCRN0 + 32 * (SCY/8 - 2)
-    ld a, [rSCY]
-    sub 16
-    srl a
-    srl a
-    srl a
-    call get_row_ptr
-
-    call enqueue_row_write
-
-    ld a, [PAGEY]
-    sub 8
-    ld [PAGEY], a
-
-    ret
-
-.scroll_down_check:
-    ; Check SCY + (SCRN_Y + 16) = PAGEY
-    ld a, [PAGEY]
-    sub SCRN_Y + 16
-    ld hl, rSCY
-    cp [hl]
-    jr nz, .scroll_left_check
-
-    ld a, [PAGEY]
+    ; HL = _SCRN0 + 32 * ((SCX/8 - 2) % 32)
+    ld a, [rSCX]
     srln a, 3
-    dec a
+    sub 2
+    and %11111
     call get_row_ptr
 
-    LOAD_MAPX
+    jr .write_row
 
+.scroll_down:
     ; C = CAMERA_Y + 18 + 1
     ld a, [CURRENT_CAMERA_Y]
     add SCRN_Y_B + 1
     ld c, a
 
+    ; HL = _SCRN0 + 32 * (SCY/8 + SCRN_Y_B + 1)
+    ld a, [rSCY]
+    srln a, 3
+    add SCRN_Y_B + 1
+    call get_row_ptr
+
+.write_row:
     call enqueue_row_write
+    ret
 
-    ld a, [PAGEY]
-    add 8
-    ld [PAGEY], a
+.scroll_horiz:
+    ; Check SCX % 8 = 0
+    ld a, [rSCX]
+    and %111
+    ret nz
 
-    ret
+    LOAD_MAPY
 
-.scroll_left_check:
-    ; If SCX = PAGEX, write map col
-    ld a, [PAGEX]
-    ld hl, rSCX
-    cp [hl]
-    jr nz, .scroll_right_check
+    ld a, [SCROLL_DIR]
+    cp DIRB_LEFT
+    jr nz, .scroll_right
 
-    ; HL = VRAM + PAGEX/8
+    ; HL = VRAM + (SCX/8 - 2) % 32
     ld hl, _SCRN0
-    ld a, [PAGEX]
+    ld a, [rSCX]
     srln a, 3
-    dec a
+    sub 2
+    and %11111
     ADD16 hl
 
-    ; B = CAMERA_X - 1
+    ; B = CAMERA_X - 2
     ld a, [CURRENT_CAMERA_X]
-    dec a
+    sub 2
     ld b, a
 
-    ; C = CAMERA_Y - SCY/8
-    LOAD_MAPY
-
-    call enqueue_col_write
-
-    ld a, [PAGEX]
-    sub 8
-    ld [PAGEX], a
-
-.scroll_right_check:
-    ; If SCX = SCRN_X - PAGEX, write map col
-    ; Check SCX + (SCRN_X + 16) = PAGEX
-    ld a, [PAGEX]
-    sub SCRN_X + 16
-    ld hl, rSCX
-    cp [hl]
-    ret nz
+    jr .write_col
 
-    ; HL = VRAM + PAGEX/8
+.scroll_right:
+    ; HL = VRAM + SCX/8 + SCRN_X_B + 1
     ld hl, _SCRN0
-    ld a, [PAGEX]
+    ld a, [rSCX]
     srl a
     srl a
     srl a
-    dec a
+    add SCRN_X_B + 1
     ADD16 hl
 
-    ; B = CAMERA_X + 20
+    ; B = CAMERA_X + 20 + 1
     ld a, [CURRENT_CAMERA_X]
     add SCRN_X_B + 1
     ld b, a
 
-    ; C = CAMERA_Y - SCY/8
-    LOAD_MAPY
-
+.write_col:
     call enqueue_col_write
-
-    ld a, [PAGEX]
-    add 8
-    ld [PAGEX], a
-
     ret
 
 Map_Update::