Add untested framework for handling fringe tile rendering

src/Anim.s

@@ -0,0 +1,66 @@
+; Animation helpers
+;
+; These provide animation sequencing and pathing support for animations.  Some function are
+; sprite-specific, but the functions are generally applicable to any kind of animation support
+; by the engine, such as swapping tiles or even just having an asynchronous method of updating
+; game data.
+;
+; Depends on the Timers and Script sub-systems
+
+
+; AnimatePath
+;
+; Moves a sprite between two keyframe point over a specificed number of steps
+;
+; X = YYXX       ; start position
+; A = YYXX       ; end position
+; Y = duration   ; number of steps from start to end (must be > 0)
+AnimatePath
+
+             pha                 ; Store the starting point
+             and   #$00FF
+             sta   AnimX0
+             pla
+             xba
+             and   #$00FF
+             sta   AnimY0
+
+             txa                 ; Store the ending point
+             and   #$00FF
+             sta   AnimX1
+             txa
+             xba
+             and   #$00FF
+             sta   AnimY1
+
+             sty   AnimDuration
+
+; Calculate the steps for the X and Y positions. This is line drawing two lines
+; at a time .  The slope of the lines are (X1 - X0) / Duration and (Y1 - Y0) / Duration.
+;
+; The tricky bit is that we *always* single-step in the "Y" direction (duration), so we
+; actaully need to use two differenct algorithms.
+;
+; If |X1 - X0| <= Duration, use a standard line-drawing approach (Bresenham's, DDA, etc.)
+; If |X1 - X0|  > Duration, use the Run-Length Slice algorithm (https://www.phatcode.net/res/224/files/html/ch36/36-02.html)
+
+             lda   AnimY
+
+:stepx       lda
+
+
+             cmp   AnimDuration  ; Handle the two cases
+
+
+
+
+
+
+
+
+
+
+
+
+
+

src/Core.s

@@ -226,6 +226,8 @@ EngineReset
                   stz       TileMapHeight
                   stz       TileMapPtr
                   stz       TileMapPtr+2
+                  stz       FringeMapPtr
+                  stz       FringeMapPtr+2
 
                   stz       BG1TileMapWidth
                   stz       BG1TileMapHeight
@@ -378,4 +380,3 @@ ReadControl       ENT
                   put       blitter/BG0.s
                   put       blitter/BG1.s
                   put       TileMap.s
-

src/Defs.s

@@ -70,12 +70,13 @@ OldBG1TileOriginY      equ   68
 TileMapWidth           equ   70
 TileMapHeight          equ   72
 TileMapPtr             equ   74
+FringeMapPtr           equ   78
 
-BG1TileMapWidth        equ   78
-BG1TileMapHeight       equ   80
-BG1TileMapPtr          equ   82
+BG1TileMapWidth        equ   82
+BG1TileMapHeight       equ   84
+BG1TileMapPtr          equ   86
 
-Next                   equ   86
+Next                   equ   90
 
 BankLoad               equ   128
 

src/Sprite.s

@@ -3,60 +3,3 @@
 ;
 ; The main point of this file to to establish calling conventions and provide a framework
 ; for blitting a range of sprite lines, instead of always the full sprite.
-
-; A = address, X = scroll_mask offset, Y = HHLL, LL = first line, HH = last line
-draw
-    sei
-    
-    cli
-    rts
-
-lines dw line0,line1,line2,line3,line4,line5,line6,line7
-
-line0
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line1
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line2
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line3
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line4
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line5
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line6
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0
-
-line7
-    lda 0
-    and #$FF00
-    ora #$00DD
-    sta 0

src/TileMap.s

@@ -313,9 +313,24 @@ _UpdateBG0TileMap
 :xloop
                    ldy   :Offset                 ; Set up the arguments and call the tile blitter
                    lda   [TileMapPtr],y
-                   iny                           ; pre-increment the address. A bit faster than two "INC DP" instructions
-                   iny
-                   sty   :Offset
+
+; Handle fringe tiles -- if the fringe bit is set, then we need to get the fringe tile index
+; and merge the tiles before rendering
+                   bit   #$TILE_FRINGE_BIT
+                   beq   :no_fringe
+                   jsr   _GetTileAddr
+                   tax
+                   lda   FringeMapPtr
+                   ora   FringeMapPtr+2
+                   beq   :no_fringe
+                   lda   [FringeMapPtr],y
+                   jsr   _GetTileAddr
+                   tay
+                   jsr   _MergeTiles
+
+:no_fringe
+                   inc   :Offset                 ; pre-increment the address.
+                   inc   :Offset
 
                    ldx   :BlkX
                    ldy   :BlkY