At 11:15 PM 7/2/2002 +0000, you wrote:
that's it. When it's moving over to the left, the top line
(and only the top line) gets cut off; I think my kernel isn't
fitting in HBLANK in the case where it's having to set
VisiblePlayerLine.
Thomas explained his definitive routine for determining when to display
sprites last fall when I was working on Death Derby.
You should try to find it in the archives.
As for the timing, I think the standard way to get around it is to use
VDEL, so that the timing for one of the sprites is no longer critical.
Here is River Raid's kernel, for instance:
; *** here starts the main kernel loop: ***
.loopKernel: ;
CPY #JET_Y ; 2 draw player jet?
BCS .skipJet0 ; 2 no, skip
LDA (shapePtr0),Y ; 5 yes, load data..
TAX ; 2 ..into x
.contJet0:
LDY blockLine ; 3
BIT roadBlock ; 3 road displayed?
BPL .noRoad ; 2 no, normal PF color
LDA RoadColorTab,Y ; 4 yes, load road colors
IF SCREENSAVER
EOR SS_XOR ; 3
.contPFColor:
AND SS_Mask ; 3
ELSE
FILL_NOP 2
.contPFColor:
FILL_NOP 1
ENDIF
STA.w temp ; 4
LDA (shapePtr1b),Y ; 5
STA GRP1 ; 3 time doesn't matter (VDELP1!)
LDA (PF1Ptr),Y ; 5
STA PF1 ; 3 @75
;--------------------------------------
; new line starts here!
; odd line:
; - set PF color
; - set P1 color
; - change PF
STA HMOVE ; 3
STX GRP0 ; 3 @2 this also updates GRP1
LDA temp ; 3
STA COLUPF ; 3 @8
LDA (colorPtr),Y ; 5
IF SCREENSAVER
EOR SS_XOR ; 3
AND SS_Mask ; 3
ELSE
FILL_NOP 4
ENDIF
STA COLUP1 ; 3 @22
LDA (PF2Ptr),Y ; 5
STA PF2 ; 3 @30
enterKernel2:
LDA (shapePtr1a),Y ; 5
STA GRP1 ; 3 time doesn't matter (VDELP1!)
LDY lineNum ; 3
DEY ; 2
BEQ .exitKernel2 ; 2
CPY #JET_Y ; 2
BCC .doJet0a ; 2
TYA ; 2
SBC missileY ; 3
AND #$F8 ; 2
BNE .skipEnable0 ; 2
LDA #ENABLE ; 2
.skipEnable0:
LDX #$00 ; 2
.contJet0a:
DEY ; 2
STY lineNum ; 3
STA WSYNC ; 3
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