Begin trying to fix map

inc/util.inc

@@ -49,3 +49,17 @@ MACRO LD16
     ld HIGH(\1), HIGH(\2)
     ld LOW(\1), LOW(\2)
 ENDM
+
+; \1 8-bit register
+; \2 Number of shifts (1-7)
+MACRO srln
+    ASSERT \2 >= 1 && \2 <= 7
+    REPT \2
+        srl \1
+    ENDR
+ENDM
+
+MACRO SLA16
+    sla LOW(\1)
+    rl HIGH(\1)
+ENDM

src/map.s

@@ -91,6 +91,40 @@ Map_Load::
 
     ret
 
+; Loads the map X-coordinate into B
+MACRO LOAD_MAPX
+    ; if SCX <= 0x7f
+    ld a, [rSCX]
+    cp $80
+    jr nc, .wrap\@
+
+    ; B = CAMERA_X - SCX/8
+    ld a, [rSCX]
+    ld b, a
+    ld a, [CURRENT_CAMERA_X]
+    srln b, 3
+    sub b
+    ld b, a
+    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\@:
+ENDM
+
 ; Update map state based on SCX/SCY
 Map_Scroll::
     ; If SCY = PAGEY, write map row
@@ -154,15 +188,7 @@ Map_Scroll::
     ld e, a
     call compute_vram_ptr
 
-    ; B = CAMERA_X - SCX/8
-    ld a, [rSCX]
-    ld b, a
-    ld a, [CURRENT_CAMERA_X]
-    srl b
-    srl b
-    srl b
-    sub b
-    ld b, a
+    LOAD_MAPX
 
     ; C = CAMERA_Y + 18 + 1
     ld a, [CURRENT_CAMERA_Y]
@@ -271,7 +297,27 @@ Map_Update::
 
     ld hl, PENDING_ROW_DATA
     ld d, SCRN_VX_B
-    MEMCPY bc, hl, d
+.copy_row:
+    ld a, [hl+]
+    ld [bc], a
+    inc bc
+
+    ; if BC % 32 == 0 (we just crossed a row boundary)
+    ld a, c
+    and %11111
+    jr nz, .copy_row1
+
+    ; BC -= 32 (reset back to beginning of row)
+    ld a, c
+    sub 32
+    ld c, a
+    ld a, b
+    sbc 0
+    ld b, a
+
+.copy_row1:
+    dec d
+    jr nz, .copy_row
 
 .update_col:
     ; Skip column update if PENDING_COL_PTR is 0
@@ -361,6 +407,14 @@ enqueue_row_write:
     ld c, SCRN_VX_B
     ld de, PENDING_ROW_DATA
 
+    ; If X > 0, increment map pointer by X
+    bit 7, b
+    jr nz, .pad_left
+
+    ld a, b
+    ADD16 hl
+    jr .copy_middle
+
     ; Note: Can skip checking BYTES_LEFT > 0 in this loop. If there were
     ; SCRN_VX_B zeros to write, then Y would be 1 greater and we would have
     ; jumped into .zero_row before reaching this code
@@ -446,6 +500,7 @@ write_map_row:
     ld a, [PENDING_ROW_PTR + 1]
     ld b, a
 
+    ; TODO: Fix
     ld hl, PENDING_ROW_DATA
     ld d, SCRN_VX_B
     MEMCPY bc, hl, d