From 9ca2b100629f4f6f1190d213c3abdced99cbc160 Mon Sep 17 00:00:00 2001
From: Forest Belton <65484+forestbelton@users.noreply.github.com>
Date: Sun, 11 Jul 2021 22:19:25 -0400
Subject: [PATCH] Update camera when left/right pressed

---
 src/main.s | 87 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 69 insertions(+), 18 deletions(-)

diff --git a/src/main.s b/src/main.s
index 57bc4d7..8273a5d 100644
--- a/src/main.s
+++ b/src/main.s
@@ -61,8 +61,22 @@ start:
     ld [PENDING_ROW_PTR], a
     ld [PENDING_ROW_PTR + 1], a
 
-    ; TODO: remove once scrolling is implemented
-    ; scroll map with arrow keys
+    call scroll_update
+
+    ; wait for vblank
+    halt
+
+    call Map_Update
+
+    ; ~160 cycles
+    ld a, HIGH(_OAM)
+    call DMA_Start
+
+    jp .loop
+
+; TODO: remove once scrolling is implemented
+scroll_update:
+; scroll map with arrow keys
     ld a, [keys]
     and PADF_UP
     jr z, .down
@@ -76,7 +90,7 @@ start:
     ld hl, CURRENT_CAMERA_Y
     ld a, [hl]
     or a
-    jr z, .vbl
+    ret z
 
 .update_up:
     ld hl, rSCY
@@ -93,7 +107,7 @@ start:
 
 .update_up_map:
     call Map_Scroll
-    jr .vbl
+    ret
 
 .down:
     ld a, [keys]
@@ -110,7 +124,7 @@ start:
     ld a, [CURRENT_CAMERA_Y]
     add 18
     cp b
-    jr z, .vbl
+    ret z
 
 .update_down:
     ld hl, rSCY
@@ -126,36 +140,73 @@ start:
 
 .update_down_map:
     call Map_Scroll
-    jr .vbl
+    ret
 
 .right:
     ld a, [keys]
     and PADF_RIGHT
     jr z, .left
 
+    ; don't scroll right if on last tile
+    ld hl, rSCX
+    ld a, [hl]
+    and %111
+    jr nz, .update_right
+
+    ld a, [CURRENT_MAP_WIDTH]
+    ld b, a
+    ld a, [CURRENT_CAMERA_X]
+    inc a
+    ; add 18
+    cp b
+    ret z
+
+.update_right:
     ld hl, rSCX
     inc [hl]
+
+    ld a, [hl]
+    and %111
+    jr nz, .update_right_map
+
+    ld a, [CURRENT_CAMERA_X]
+    inc a
+    ld [CURRENT_CAMERA_X], a
+
+.update_right_map:
     call Map_Scroll
+    ret
 
 .left:
     ld a, [keys]
     and PADF_LEFT
-    jr z, .vbl
+    ret z
 
+    ; don't scroll left if on last tile
     ld hl, rSCX
-    dec [hl]
+    ld a, [hl]
+    and %111
+    cp %111
+    jr nz, .update_left
 
-    call Map_Scroll
-    ; call Player_Update
+    ld hl, CURRENT_CAMERA_X
+    ld a, [hl]
+    or a
+    ret z
 
-    ; wait for vblank
-.vbl:
-    halt
+.update_left:
+    ld hl, rSCX
+    dec [hl]
 
-    call Map_Update
+    ld a, [hl]
+    and %111
+    cp %111
+    jr nz, .update_left_map
 
-    ; ~160 cycles
-    ld a, HIGH(_OAM)
-    call DMA_Start
+    ld a, [CURRENT_CAMERA_X]
+    dec a
+    ld [CURRENT_CAMERA_X], a
 
-    jp .loop
+.update_left_map:
+    call Map_Scroll
+    ret