Implement full per-scanline offset support for BG1

macros/GTE.Macs.s

@@ -174,6 +174,7 @@ OVERLAY_BELOW          equ   $4000      ; Overlay is drawn below scanline sprite
 
 ; GetAddress table IDs
 scanlineHorzOffset     equ   $0001
+scanlineHorzOffset2    equ   $0002
 
 ; Tile constants
 ; TILE_RESERVED_BIT      equ   $8000

src/Defs.s

@@ -195,7 +195,8 @@ DIRTY_BIT_BG1_REFRESH  equ   $0020
 DIRTY_BIT_SPRITE_ARRAY equ   $0040
 
 ; GetAddress table IDs
-scanlineHorzOffset     equ   $0001        ; table of 416 words, a double-array of scanline offset values. Must be 0, 163
+scanlineHorzOffset     equ   $0001        ; Table of 416 words, a double-array of scanline offset values. Values must be in range [0, 163]
+scanlineHorzOffset2    equ   $0002        ; Table of 416 words, a double-array of scanline offset values. Values must be in range [0, 163]
 
 ; Script definition
 YIELD                  equ   $8000
@@ -297,6 +298,7 @@ _DirectListBottom EXT
 
 StartXMod164Tbl   EXT
 LastOffsetTbl     EXT
+BG1StartXMod164Tbl EXT
 
 ; Tool error codes
 NO_TIMERS_AVAILABLE  equ  10

src/Tool.s

@@ -886,13 +886,23 @@ _TSGetAddress
 
                 lda     :tblId,s
                 cmp     #scanlineHorzOffset
-                bne     :out
+                bne     :next_1
 
                 lda     StartXMod164Tbl
                 sta     :output,s
                 lda     StartXMod164Tbl+2
                 sta     :output+2,s
+                bra     :out
 
+:next_1         cmp     #scanlineHorzOffset2
+                bne     :next_2
+
+                lda     BG1StartXMod164Tbl
+                sta     :output,s
+                lda     BG1StartXMod164Tbl+2
+                sta     :output+2,s
+                bra     :out
+:next_2
 :out
                 _TSExit #0;#2
 
@@ -904,12 +914,24 @@ _TSSetAddress
                 _TSEntry
                 lda     :tblId,s
                 cmp     #scanlineHorzOffset
-                bne     :out
+                bne     :next_1
 
                 lda     :ptr,s
                 sta     StartXMod164Tbl
                 lda     :ptr+2,s
                 sta     StartXMod164Tbl+2
+                bra     :out
+
+:next_1
+                cmp     #scanlineHorzOffset2
+                bne     :next_2
+
+                lda     :ptr,s
+                sta     BG1StartXMod164Tbl
+                lda     :ptr+2,s
+                sta     BG1StartXMod164Tbl+2
+                bra     :out
+:next_2
 :out
                 _TSExit #0;#6
 

src/static/TileStore.s

@@ -388,13 +388,17 @@ BG1YOffsetTable   ENT
 ;                  dw     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
                   --^
 
-; Per-scanline offsets for BG0
+; Pointer to per-scanline offsets for BG0
 StartXMod164Tbl   ENT
                   dw    0,0
 
 LastOffsetTbl     ENT
                   ds    416
 
+; Pointer to per-scanline offsets for BG1
+BG1StartXMod164Tbl ENT
+                  dw    0,0
+
 ; Other Toolset variables
 OneSecondCounter  ENT
                   dw        0