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Fix some small bugs with tile rendering; tiles display but crash after scrolling 8 bytes
This commit is contained in:
Lucas Scharenbroich
parent
d01791b440
commit
39639d54b5
18
src/Render.s
18
src/Render.s
@ -65,14 +65,21 @@ Render
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; used in all of the other loops
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jsr _ApplyBG0YPos ; Set stack addresses for the virtual lines to the physical screen
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; _ApplyBG0Xpos need to be split because we have to set the offsets, then draw in any updated tiles, and
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; finally patch out the code field. Right now, the BRA operand is getting overwritten by tile data.
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jsr _ApplyBG0XPosPre
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lda #$FFFF ; Force a tile refresh
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jsr _UpdateBG0TileMap
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jsr _ApplyBG0XPos ; Patch the PEA instructions with exit BRA opcode
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; jsr _ApplyBG1YPos ; Adjust the index values into the BG1 bank buffer
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; jsr _ApplyBG1XPos ; Adjust the direct page pointers to the BG1 bank
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; Copy any tiles that have come into view
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jsr _UpdateBG0TileMap
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; The code fields are locked in now and reder to be rendered
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jsr ShadowOff
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@ -98,3 +105,10 @@ Render
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rts
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@ -2,7 +2,7 @@
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;
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; This module contains higher-level functions than the low-level tile rendering routines. The
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; goal here is to take a rectangular tilemap data structure and efficiently render it into
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; code buffer. Especially inportant is to only draw new tiles as they come into view.
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; code buffer. Especially important is to only draw new tiles as they come into view.
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;
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; Also, we maintain a tilemap cache to track the current state of the tiles rendered into
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; the code field so if, by chance, a tile that comes into view is the same as a tile that
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@ -10,6 +10,13 @@
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; in actual games since the primary background is often large empty areas, or runs
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; of repeating tiles.
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; _UpdateBG0TileMap
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;
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; Fill in dirty tiles into the BG0 buffer.
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;
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; A = $FFFF re-render the entire playfield. Otherwise only render difference from the old
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; coordinates.
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_UpdateBG0TileMap
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:Left equ tmp0
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:Right equ tmp1
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@ -31,29 +38,38 @@ _UpdateBG0TileMap
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:BlkX equ tmp12
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:BlkY equ tmp13
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:Refresh equ tmp14
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cmp #$FFFF
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lda #0
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rol
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sta :Refresh ; 1 if A = $FFFF, 0 otherwise
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lda StartY ; calculate the tile index of the current location
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and #$FFF8
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lsr
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lsr
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lsr
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sta BG0TileOriginY
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lda OldStartY
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and #$FFF8
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lsr
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lsr
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lsr
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sta OldBG0TileOriginY
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lda StartX
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and #$FFF8
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and #$FFFC
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lsr
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lsr
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sta BG0TileOriginX
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lda OldStartX
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and #$FFF8
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and #$FFFC
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lsr
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lsr
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sta OldBG0TileOriginY
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sta OldBG0TileOriginX
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; Figure out the two rectangular regions that need to be updated. We check for changes in Y-direction
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; first because it's a bit more efficient to redraw tiles in long horizontal strips, because we do not
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@ -83,6 +99,12 @@ _UpdateBG0TileMap
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lda ScreenTileHeight
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sta :Bottom
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; If we are supposed to refresh the while field, just do that and return
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lda :Refresh
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beq :NoRefresh
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jmp :DrawRectBG0 ; Let the DrawRectBG0 RTS take care of the return for us
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:NoRefresh
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lda BG0TileOriginY
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cmp OldBG0TileOriginY
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beq :NoYUpdate ; if equal, don't change Y
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@ -323,3 +345,13 @@ _UpdateBG0TileMap
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bne :loop
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rts
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@ -125,6 +125,15 @@ _RestoreBG0Opcodes
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; x_exit = (164 - x) % 164
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; x_enter = (164 - x - width) % 164
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;
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; Small routine to put the data in a consistent state. Called before any routines need to draw on
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; the code buffer, but before we patch out the instructions.
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_ApplyBG0XPosPre
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lda StartX ; This is the starting byte offset (0 - 163)
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jsr Mod164
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sta StartXMod164
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rts
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_ApplyBG0XPos
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:virt_line equ tmp1
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@ -189,11 +198,7 @@ _ApplyBG0XPos
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;
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; So, in short, the entry tile position is rounded up from the x-position and the exit
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; tile position is rounded down.
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lda StartX ; This is the starting byte offset (0 - 163)
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jsr Mod164 ;
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sta StartXMod164
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;
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; Now, the left edge of the screen is pushed last, so we need to exit one instruction *after*
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; the location (163 - StartX % 164)
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;
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@ -215,7 +220,6 @@ _ApplyBG0XPos
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; | JMP loop |
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; +-----------+
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lda #163
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sec
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sbc StartXMod164
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@ -746,3 +750,5 @@ SetCodeEntryOpcode
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@ -47,7 +47,7 @@ CopyTile
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plb ; set the bank
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pla ; pop the tile ID
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jsr :ClearTile ; :_CopyTile
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jsr :CopyTileMem0
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plx ; pop the x-register
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plb ; restore the data bank and return
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@ -145,6 +145,7 @@ CopyTile
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:CopyTileMem sec
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sbc #$0010
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:CopyTileMem0
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asl
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asl
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asl
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@ -235,3 +236,6 @@ CopyTile
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sta $7003,y
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rep #$20
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rts
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