Apple-2gs-SW/iigs-game-engine
1
0
Fork 0
mirror of https://github.com/lscharen/iigs-game-engine.git synced 2024-06-03 14:29:33 +00:00
Code Issues Projects Releases Wiki Activity

Horizontal scrolling no longer crashes; still have incorrect edge rendering

Browse Source
This commit is contained in:
Lucas Scharenbroich 2021-07-15 15:30:24 -05:00
parent b6fadedfc7
commit 26e39e3bfd
3 changed files with 41 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/App.Main.s
View File

@ -392,6 +392,20 @@ VBLTASK hex 00000000
; Blitter initialization
BlitInit
stz ScreenHeight
stz ScreenWidth
stz ScreenY0
stz ScreenY1
stz ScreenX0
stz ScreenX1
stz ScreenTileHeight
stz ScreenTileWidth
stz StartX
stz StartY
stz EngineMode
stz DirtyBits
stz LastPatchOffset
]step equ 0
lup 13
ldx #BlitBuff
@ -747,5 +761,6 @@ qtRec adrl $0000

2
src/blitter/DirectPage.s
View File

@ -13,6 +13,7 @@ StartY equ 18 ; Which code buffer line is the top of the s
EngineMode equ 20 ; Defined the mode/capabilities that are enabled
; bit 0: 0 = Single Background, 1 = Parallax
DirtyBits equ 22 ; Identify values that have changed between frames
LastPatchOffset equ 24 ; Offset into code field that was patched with BRA instructions
BG1DataBank equ 24 ; Data bank that holds BG1 layer data
BlitterDP equ 25 ; Direct page address the holder blitter data
@ -52,3 +53,4 @@ DIRTY_BIT_BG1_Y equ $0008

32
src/blitter/Horz.s
View File

@ -26,7 +26,7 @@ SetBG0XPos
stx OldStartX ; First change, so preserve the value
:out rts
; Simple function that restores the saved opcode that are stached in _applyBG0Xpos. It is
; Simple function that restores the saved opcode that are stashed in _applyBG0Xpos. It is
; very important that opcodes are restored before new ones are inserted, because there is
; only one, fixed storage location and old values will be overwritten if operations are not
; performed in order.
@ -51,13 +51,9 @@ _RestoreBG0Opcodes
asl
sta :lines_left_x2
lda StartX ; Repeat with adding the screen width
clc ; to calculate the exit column
adc ScreenWidth
and #$FFFE
tax
lda Col2CodeOffset,X
lda LastPatchOffset ; If zero, there are no saved opcodes
sta :exit_offset
beq :loop
:loop
ldx :virt_line_x2
@ -99,7 +95,9 @@ _RestoreBG0Opcodes
sta :lines_left_x2
jne :loop
stz LastPatchOffset ; Clear the value once completed
:out
phk
plb
rts
@ -141,8 +139,13 @@ _ApplyBG0XPos
:opcode equ tmp0
:odd_entry_offset equ tmp10
; This code is fairly succinct. See the corresponding code in Vert.s for more detailed comments.
; If there are saved opcodes that have not been restored, do not run this routine
lda LastPatchOffset
beq :ok
rts
; This code is fairly succinct. See the corresponding code in Vert.s for more detailed comments.
:ok
lda StartY ; This is the base line of the virtual screen
sta :virt_line ; Keep track of it
@ -242,6 +245,7 @@ _ApplyBG0XPos
sta :exit_bra
lda Col2CodeOffset,X
sta :exit_offset
sta LastPatchOffset ; Cache as a flag for later
bra :do_entry
; This is the odd code path
@ -251,6 +255,7 @@ _ApplyBG0XPos
sta :exit_bra
lda Col2CodeOffset,X
sta :exit_offset
sta LastPatchOffset ; Cache as a flag for later
; Calculate the entry byte into the code field
:do_entry tya ; reload 163 - x % 164
@ -743,6 +748,17 @@ SetCodeEntryOpcode