From 8d31720e1c61300ea5a94be6b74ea467d31acb65 Mon Sep 17 00:00:00 2001
From: Lucas Scharenbroich <lscharen@prowestgis.com>
Date: Sat, 7 Aug 2021 21:21:28 -0500
Subject: [PATCH] Add an extra column when coordinates are not tile-aligned

---
 src/TileMap.s | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/TileMap.s b/src/TileMap.s
index 04e36b7..b3744d9 100644
--- a/src/TileMap.s
+++ b/src/TileMap.s
@@ -94,12 +94,19 @@ _UpdateBG0TileMap
                    stz   :Left              ; prepare to do the entire screen
                    lda   ScreenTileWidth    ; and then whack off the parts
                    sta   :Right             ; that are not needed
+                   lda   StartX
+                   and   #$0003             ; If not tile-aligned, then we need to draw one extra column
+                   beq   *+2
+                   inc   :Right
 
                    stz   :Top
                    lda   ScreenTileHeight
                    sta   :Bottom
+                   and   #$0007
+                   beq   *+2
+                   inc   :Bottom
 
-; If we are supposed to refresh the while field, just do that and return
+; If we are supposed to refresh the whole field, just do that and return
                    lda   :Refresh
                    beq   :NoRefresh
                    jmp   :DrawRectBG0       ; Let the DrawRectBG0 RTS take care of the return for us
@@ -371,3 +378,6 @@ _UpdateBG0TileMap
 
 
 
+
+
+