Finish simplifying map API

src/map.s

@@ -88,23 +88,57 @@ Map_Load::
 
 ; Scroll the map upwards
 ; @param d The amount to scroll by (0 < d < 8)
+;
+; SCY_T = SCY % 8;
+; if CAMERA_Y = 0 {
+;     if SCY_T != 0 {
+;         SCY -= MIN(D, SCY_T);
+;     }
+;     return;
+; }
+; SCY -= D;
+; if SCY_T - D < 0 {
+;     CAMERA_Y -= 1;
+;     Map_ScrollRow(CAMERA_X - 2, CAMERA_Y - 2);
+; }
 Map_ScrollUp::
-    ; Check whether we crossed tile boundary
     ld a, [rSCY]
     and %111
-    cp d
-    jr nc, .done
 
-    ; Don't scroll if at top tile
+    add sp, -1
+    ld hl, sp + 0
+    ld [hl], a
+
     ld a, [CURRENT_CAMERA_Y]
     or a
-    ret z
+    jr nz, .scroll
+
+    ld hl, sp + 0
+    ld a, [hl]
+    or a
+    jr z, .done
 
+    ld b, d
+    call min
+    ld d, a
+    ld a, [rSCY]
+    sub d
+    ld [rSCY], a
+    jr .done
+
+.scroll:
     ld a, [rSCY]
     sub d
     ld [rSCY], a
 
+    ; Check SCY_T - D < 0
+    ld hl, sp + 0
+    ld a, [hl]
+    sub d
+    jr nc, .done
+
     ; CAMERA_Y -= 1
+    ld a, [CURRENT_CAMERA_Y]
     dec a
     ld [CURRENT_CAMERA_Y], a
 
@@ -123,57 +157,73 @@ Map_ScrollUp::
     srln a, 3
     sub 2
 
+    add sp, 1
     jr Map_ScrollRow
 
 .done:
-    ld a, [rSCY]
-    sub d
-    ld [rSCY], a
+    add sp, 1
     ret
 
 
 
+; Map_ScrollDown(D)
+;
+; SCY_T = SCY % 8;
+; if CAMERA_Y + 18 = MAP_HEIGHT {
+;     if SCY_T != 0 {
+;         SCY += MIN(D, 8 - SCY_T);
+;     }
+;     return;
+; }
+; SCY += D;
+; if SCY_T + D >= 8 {
+;     CAMERA_Y += 1;
+;     Map_ScrollRow(CAMERA_X - 2, CAMERA_Y + 18 + 1);
+; }
 Map_ScrollDown::
-    ; Don't scroll if at bottom tile
+    ld a, [rSCY]
+    and %111
+
+    add sp, -1
+    ld hl, sp + 0
+    ld [hl], a
+
     ld a, [CURRENT_CAMERA_Y]
     add SCRN_Y_B
     ld hl, CURRENT_MAP_HEIGHT
     cp [hl]
-    jr nz, .down
+    jr nz, .scroll
+
+    ld hl, sp + 0
+    ld a, [hl]
+    or a
+    jr z, .done
 
+    sub 8
+    cpl
+
+    ld b, d
+    call min
+    ld d, a
     ld a, [rSCY]
     add d
-    and %111
     ld [rSCY], a
-    ret
+    jr .done
 
-    ; Check whether we crossed tile boundary
-.down:
+.scroll:
     ld a, [rSCY]
-    and %111
     add d
-    cp 8
-    jr c, .done
-
-    ; TODO:
-    ; if CAMERA_Y + 18 = MAP_HEIGHT {
-    ;     if SCY % 8 != 0 {
-    ;         SCY += MIN(D, 8 - SCY % 8)
-    ;     }
-    ;     return
-    ; }
-    ; if SCY % 8 + D > 8 {
-    ;     SCY += D
-    ;     LOAD_COLUMN(CAMERA_X - 2, CAMERA_Y + 18 + 1);
-    ; } else {
-    ;     SCY += D
-    ; }
+    ld [rSCY], a
 
-    ld a, [rSCY]
+    ; Check SCY_T + D < 8
+    ld hl, sp + 0
+    ld a, [hl]
     add d
-    ld [rSCY], a
+    cp 8
+    jr c, .done
 
     ; CAMERA_Y += 1
+    ld a, [CURRENT_CAMERA_Y]
     inc a
     ld [CURRENT_CAMERA_Y], a
 
@@ -192,12 +242,11 @@ Map_ScrollDown::
     srln a, 3
     add SCRN_Y_B + 1
 
+    add sp, 1
     jr Map_ScrollRow
 
 .done:
-    ld a, [rSCY]
-    add d
-    ld [rSCY], a
+    add sp, 1
     ret
 
 
@@ -222,21 +271,47 @@ Map_ScrollRow:
     call enqueue_row_write
     ret
 
+
+
 Map_ScrollLeft::
-    ; Check whether we crossed tile boundary
     ld a, [rSCX]
     and %111
-    cp d
-    jr nc, .done
 
+    add sp, -1
+    ld hl, sp + 0
+    ld [hl], a
+
+    ld a, [CURRENT_CAMERA_X]
+    or a
+    jr nz, .scroll
+
+    ld hl, sp + 0
+    ld a, [hl]
+    or a
+    jr z, .done
+
+    ld b, d
+    call min
+    ld d, a
     ld a, [rSCX]
     sub d
     ld [rSCX], a
+    jr .done
+
+.scroll:
+    ld a, [rSCX]
+    sub d
+    ld [rSCX], a
+
+    ; Check SCX_T - D < 0
+    ld hl, sp + 0
+    ld a, [hl]
+    sub d
+    jr nc, .done
 
-    ; Don't scroll if at left tile
     ld a, [CURRENT_CAMERA_X]
-    or a
-    ret z
+    dec a
+    ld [CURRENT_CAMERA_X], a
 
     ld a, [rSCY]
     sub 16
@@ -254,37 +329,61 @@ Map_ScrollLeft::
     ld a, [rSCX]
     srln a, 3
     sub 2
+    ADD16 hl
 
+    add sp, 1
     jr Map_ScrollColumn
 
 .done:
-    ld a, [rSCX]
-    sub d
-    ld [rSCX], a
+    add sp, 1
     ret
 
 
 
 Map_ScrollRight::
-    ; Check whether we crossed tile boundary
     ld a, [rSCX]
     and %111
+
+    add sp, -1
+    ld hl, sp + 0
+    ld [hl], a
+
+    ld a, [CURRENT_CAMERA_X]
+    add SCRN_X_B
+    ld hl, CURRENT_MAP_WIDTH
+    cp [hl]
+    jr nz, .scroll
+
+    ld hl, sp + 0
+    ld a, [hl]
+    or a
+    jr z, .done
+
+    sub 8
+    cpl
+
+    ld b, d
+    call min
+    ld d, a
+    ld a, [rSCX]
     add d
-    cp 8
-    jr nc, .done
+    ld [rSCX], a
+    jr .done
 
+.scroll:
     ld a, [rSCX]
     add d
     ld [rSCX], a
 
-    ; Don't scroll if at bottom tile
-    ld a, [CURRENT_CAMERA_X]
-    inc a
-    ld hl, CURRENT_MAP_WIDTH
-    cp [hl]
-    ret z
+    ; Check SCX_T + D < 8
+    ld hl, sp + 0
+    ld a, [hl]
+    add d
+    cp 8
+    jr c, .done
 
     ; CAMERA_X += 1
+    ld a, [CURRENT_CAMERA_X]
     inc a
     ld [CURRENT_CAMERA_X], a
 
@@ -306,14 +405,14 @@ Map_ScrollRight::
     srl a
     srl a
     add SCRN_X_B + 1
-    ld e, a
+    and %11111
+    ADD16 hl
 
+    add sp, 1
     jr Map_ScrollColumn
 
 .done:
-    ld a, [rSCX]
-    add d
-    ld [rSCX], a
+    add sp, 1
     ret
 
 

src/util.s

@@ -54,3 +54,14 @@ div10::
     srl a
     srl a
     ret
+
+; Compute the minimum of two unsigned integers
+; @param a First integer
+; @param b Second integer
+; @returns The minimum of the two in A
+; 21 cycles if A < B, 26 cycles otherwise
+min::
+    cp b
+    ret c
+    ld a, b
+    ret