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keen: optimize drawing a bit

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This commit is contained in:
Vince Weaver 2024-03-14 00:24:03 -04:00
parent 8ad4414424
commit 9d27583f11
2 changed files with 35 additions and 36 deletions
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67
games/keen/draw_tilemap.s
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@ -5,19 +5,17 @@
draw_tilemap: draw_tilemap:
ldy #0 ; current screen Ypos to draw at ldy #0 ; current screen Ypos to draw at
sty tiley ; (we draw two at a time as lores sty TILEY ; (we draw two at a time as lores
; is two blocks per byte) ; is two blocks per byte)
ldx #1 ; offset in current screen ldx #0 ; offset in current tilemap
; FIXME: why is this 1? stx TILEMAP_OFFSET ;
stx tilemap_offset ; tilemap
lda #0 ; init odd/even lda #0 ; init odd/even
sta tile_odd ; (tiles are two rows tall) sta TILE_ODD ; (tiles are two rows tall)
tilemap_outer_loop: tilemap_outer_loop:
ldy tiley ; setup output pointer to current Ypos ldy TILEY ; setup output pointer to current Ypos
lda gr_offsets,Y ; get address of start of row lda gr_offsets,Y ; get address of start of row
sta GBASL sta GBASL
@ -29,73 +27,70 @@ tilemap_outer_loop:
ldy #0 ; draw row from 0..40 ldy #0 ; draw row from 0..40
; ldy #6 ; we draw in window 6->34
tilemap_loop: tilemap_loop:
ldx tilemap_offset ; get actual tile number ldx TILEMAP_OFFSET ; get actual tile number
lda tilemap,X ; from tilemap lda tilemap,X ; from tilemap
asl ; *4 ; point to tile to draw (4 bytes each) asl ; *4 ; point to tile to draw (4 bytes each)
asl asl
tax tax
lda tile_odd ; lda TILE_ODD ;
beq not_odd_line beq not_odd_line
inx inx
inx inx
not_odd_line: not_odd_line:
lda tiles,X ; draw two tiles ; draw two tiles
; note we don't handle transparency in the keen engine
; cmp #$AA ; transparency
; beq skip_tile1
lda tiles,X
sta (GBASL),Y ; draw upper right sta (GBASL),Y ; draw upper right
;skip_tile1:
iny iny
lda tiles+1,X lda tiles+1,X
; cmp #$AA ; transparency
; beq skip_tile2
sta (GBASL),Y ; draw upper left sta (GBASL),Y ; draw upper left
;skip_tile2:
iny iny
inc tilemap_offset inc TILEMAP_OFFSET
cpy #40 ; until done cpy #40 ; until done
; cpy #34 ; until done
bne tilemap_loop bne tilemap_loop
; row is done, move to next line ; row is done, move to next line
lda tile_odd ; toggle odd/even lda TILE_ODD ; toggle odd/even
eor #$1 ; (should we just add/mask?) eor #$1 ; (should we just add/mask?)
sta tile_odd sta TILE_ODD
bne move_to_odd_line bne move_to_odd_line
; move ahead to next row ; move ahead to next row
; for even line we're already pointing to next
move_to_even_line: move_to_even_line:
lda tilemap_offset ; lda TILEMAP_OFFSET
clc ; clc
adc #0 ; adc #0
jmp done_move_to_line jmp done_move_to_line
; FIXME: skip this totally
; reset back to beginning of line to display it again ; reset back to beginning of line to display it again
move_to_odd_line: move_to_odd_line:
lda tilemap_offset lda TILEMAP_OFFSET
sec sec
; sbc #14 sbc #TILE_COLS ; subtract off length of row
sbc #20 ; ? sta TILEMAP_OFFSET
done_move_to_line: done_move_to_line:
sta tilemap_offset
ldy tiley ; move to next output line
ldy TILEY ; move to next output line
iny iny
iny iny
sty tiley sty TILEY
cpy #48 ; check if at end cpy #48 ; check if at end
; cpy #40 ; check if at end ; cpy #40 ; check if at end
@ -104,9 +99,9 @@ done_move_to_line:
rts rts
; these should probably be in the zero page ; these should probably be in the zero page
tilemap_offset: .byte $00 ;tilemap_offset: .byte $00
tile_odd: .byte $00 ;tile_odd: .byte $00
tiley: .byte $00 ;tiley: .byte $00
;=================================== ;===================================

4
games/keen/zp.inc
View File

@ -126,6 +126,10 @@ DOOR_ACTIVATED = $9B
LASER_TILE = $9C LASER_TILE = $9C
TILE_TEMP = $9D TILE_TEMP = $9D
TILEY = $9E
TILE_ODD = $9F
TILEMAP_OFFSET = $A0
; done game puzzle state ; done game puzzle state