Implement scrolling left

src/map.s

@@ -136,7 +136,7 @@ Map_Scroll::
     sub 8
     ld [PAGEY], a
 
-    jr .done
+    jp .done
 
 .scroll_down_check:
     ; Check SCY + (SCRN_Y + 16) = PAGEY
@@ -144,7 +144,7 @@ Map_Scroll::
     sub SCRN_Y + 16
     ld hl, rSCY
     cp [hl]
-    jr nz, .scroll_right_check
+    jr nz, .scroll_left_check
 
     ld a, [PAGEY]
     srl a
@@ -177,11 +177,45 @@ Map_Scroll::
 
     jr .done
 
-    ; If SCX = PAGEX, write map col
 .scroll_left_check:
+    ; If SCX = PAGEX, write map col
+    ld a, [PAGEX]
+    ld hl, rSCX
+    cp [hl]
+    jr nz, .scroll_right_check
+
+    ; HL = VRAM + PAGEX/8
+    ld hl, _SCRN0
+    ld a, [PAGEX]
+    srl a
+    srl a
+    srl a
+    dec a
+    ADD16 hl
+
+    ; B = CAMERA_X - 1
+    ld a, [CURRENT_CAMERA_X]
+    dec a
+    ld b, a
+
+    ; C = CAMERA_Y - SCY/8
+    ld a, [rSCY]
+    ld c, a
+    ld a, [CURRENT_CAMERA_Y]
+    srl c
+    srl c
+    srl c
+    sub c
+    ld c, a
+
+    call enqueue_col_write
+
+    ld a, [PAGEX]
+    sub 8
+    ld [PAGEX], a
 
-    ; If SCX = SCRN_X - PAGEX, write map col
 .scroll_right_check:
+    ; If SCX = SCRN_X - PAGEX, write map col
     ; Check SCX + (SCRN_X + 16) = PAGEX
     ld a, [PAGEX]
     sub SCRN_X + 16
@@ -211,7 +245,6 @@ Map_Scroll::
     srl c
     srl c
     sub c
-    ; dec a
     ld c, a
 
     call enqueue_col_write