Sparse Invaders Source Screen.txt - simondotm/stardot-wiki GitHub Wiki
Screen Functionality. This includes displaying on screen messages, score and clearing the screen. This file also contains support functionality for handling the score etc.
the score is processed simply as you will notice once seeing the code, it's handled numbers up to 9999 which is more then enough for invaders.
;-------------------------------------------------------------------------------
; ScreenFunctionality
; Written by Neil Beresford.
;
; Copyright 2008,2009 Neil Beresford
;
; This file is part of Sparse Invaders.
; Sparse Invaders is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; Sparse Invaders is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with Sparse Invaders. If not, see <http://www.gnu.org/licenses/>.
;
;
;
;-------------------------------------------------------------------------------
.require "Constands"
.require "Macros"
;-------------------------------------------------------------------------------
;-------------------------------------------------------------------------------
SCREEN_UPDATE_COUNT - this is the delay before update the score.
.alias SCREEN_UPDATE_COUNT 5
UpdateScreen updates the game on screen items like number of lives left and score. Please note the use of the SCREEN_UPDATE, this means that screen information is only updated every 5 game frames. This reduces unwanted drawing every frame, as the area of screen where this is drawn isn't drawn over. This could be a little smarter - and just be flagged when needed to be updated. However as killing an invader increases the score, this function would generally be called as much as it is.
;-------------------------------------------------------------------------------
; UpdateScreen -
; Invaders screen update, score etc
;
;-------------------------------------------------------------------------------
UpdateScreen:
; check to see if update to screen needed...
LDA SCREEN_UPDATE
BEQ US_Update
RTS
US_Update:
; update the player lifes
LDA PLAYER_LIFES
STA SCRATCH3
LDA #39
LDX #1
STX SCRATCH4
US_Lives:
LDA #39
LDX SCRATCH4
LDY #29
jsr BLockDrawer.BlockDraw
INC SCRATCH4
DEC SCRATCH3
BNE US_Lives
US_ClearRest:
LDA #40
LDX SCRATCH4
LDY #29
jsr BLockDrawer.BlockDraw
INC SCRATCH4
LDA SCRATCH4
CMP #11
BNE US_ClearRest
; reset count, this means screen update every 5 frames
LDA #SCREEN_UPDATE_COUNT
STA SCREEN_UPDATE
; check to see score addition needed...
LDA SCORE_ADDITION
BEQ US_End
; dec the score and then update the values ...
DEC SCORE_ADDITION
; use X for clearer...
LDX #0
; inc the units, if less then 10, then update units only
INC ScreenScore+3
LDA ScreenScore+3
CMP #10
BCC US_D000X
STX ScreenScore+3
; inc the tens, if less then 10, then update tens and units only
INC ScreenScore+2
LDA ScreenScore+2
CMP #10
BCC US_D00X0
STX ScreenScore+2
; inc the hundreads, if less then 10, then update hundreds tens and units only
INC ScreenScore+1
LDA ScreenScore+1
CMP #10
BCC US_D0X00
STX ScreenScore+1
; inc the thousands, then update all values
INC ScreenScore
LDA ScreenScore
CMP #10
BCC US_DX000
; score wrap around -
STX ScreenScore
US_DX000: ; update the thousands
LDA ScreenScore
LDX #15
LDY #29
jsr BLockDrawer.BlockDraw
US_D0X00: ; update the hundreds
LDA ScreenScore+1
LDX #16
LDY #29
jsr BLockDrawer.BlockDraw
US_D00X0: ; update the tens
LDA ScreenScore+2
LDX #17
LDY #29
jsr BLockDrawer.BlockDraw
US_D000X: ; update the units
LDA ScreenScore+3
LDX #18
LDY #29
jsr BLockDrawer.BlockDraw
US_End:
RTS
AdjustScore updates the score using SCORE_ADDITION. Any score achived would be added to this value - and the score would increment accordingly. The speed of the increment is fast enough as to keep up with the scores achived within Invaders.
;-------------------------------------------------------------------------------
; AdjustScore -
; Updates the score value only...
;-------------------------------------------------------------------------------
AdjustScore:
; check to see score addition needed...
LDA SCORE_ADDITION
BEQ US_End
; dec the score and then update the values ...
DEC SCORE_ADDITION
; use X for clearer...
LDX #0
; inc the units, if less then 10, then update units only
INC ScreenScore+3
LDA ScreenScore+3
CMP #10
BCC AS_end
STX ScreenScore+3
; inc the tens, if less then 10, then update tens and units only
INC ScreenScore+2
LDA ScreenScore+2
CMP #10
BCC AS_end
STX ScreenScore+2
; inc the hundreads, if less then 10, then update hundreds tens and units only
INC ScreenScore+1
LDA ScreenScore+1
CMP #10
BCC AS_end
STX ScreenScore+1
; inc the thousands, then update all values
INC ScreenScore
LDA ScreenScore
CMP #10
BCC AS_end
; score wrap around -
STX ScreenScore
AS_end:
RTS
DrawScore jumps into the score drawing functionality.
;-------------------------------------------------------------------------------
; DrawScore -
; Updates the score on the screen...
;
;-------------------------------------------------------------------------------
DrawScore:
JMP US_DX000 ; i'M SURE this label makes sence, just give me a moment ... ;-)
;-------------------------------------------------------------------------------
ClearScore clears the stored values.
ClearScore:
LDA #0
STA ScreenScore
STA ScreenScore+1
STA ScreenScore+2
STA ScreenScore+3
RTS
ScreenScore:
.byte 0,0,0,0
Screen_CopyScoreToString converts the score into ascii and stores in the string (USERPTR points to this)
;-------------------------------------------------------------------------------
; Screen_CopyScoreToString:
; USERPTR - points to string
;-------------------------------------------------------------------------------
Screen_CopyScoreToString:
LDY #0
LDA ScreenScore
CLC
ADC #48
STA (USERPTR),Y
INY
LDA ScreenScore+1
CLC
ADC #48
STA (USERPTR),Y
INY
LDA ScreenScore+2
CLC
ADC #48
STA (USERPTR),Y
INY
LDA ScreenScore+3
CLC
ADC #48
STA (USERPTR),Y
RTS
Screen_PositionedMessage displays the string onto the screen. The first two bytes are screen position then follows the NULL terminated string.
;-------------------------------------------------------------------------------
; Screen_PositionedMessage:
; displays message, using blocks
; No gramma please in string - and only lowercase and numbers!
; USERPTR - string to display... first two chars position...
;-------------------------------------------------------------------------------
Screen_PositionedMessage:
LDY #0
LDA (USERPTR),Y
STA SCRATCH2
INY
LDA (USERPTR),Y
INY
STA SCRATCH3
JMP SM_Loop
;-------------------------------------------------------------------------------
; Screen_Message -
; displays message, using blocks (starting at 10)
; zero terminated.
; No gramma please in string - and only lowercase!
; USERPTR - string to display...
; x - xpos in 8x8 blocks
; y - ypos in 8x8 blocks
;-------------------------------------------------------------------------------
Screen_Message:
STX SCRATCH2
STY SCRATCH3
LDY #0
SM_loop:
LDA (USERPTR),Y
BEQ SM_end
CMP #32 ; space value ...
BNE SM_checknum
; DRAW SPACE ...
STY SCRATCH4
LDA #40
LDX SCRATCH2
LDY SCRATCH3
JSR BlockDrawer.BlockDraw
LDY SCRATCH4
JMP SM_next
SM_checknum:
CMP #96
BCS SM_char
SEC
SBC #48
JMP SM_draw
SM_char:
SEC
SBC #97-10 ; lower 'a' then plus the numbers
SM_draw:
STY SCRATCH4
LDX SCRATCH2
LDY SCRATCH3
JSR BlockDrawer.BlockDraw
LDY SCRATCH4
SM_Next:
INC SCRATCH2
INY
JMP SM_Loop
SM_end:
RTS
Screen_Clear clears the full screen, setting it to colour ZERO (black in game)
;-------------------------------------------------------------------------------
; Screen_Clear -
; clears the screen to colour zero
;
;-------------------------------------------------------------------------------
Screen_Clear:
LDA #SCREENLOW
STA ScreenClearAddPtr+1
LDA #SCREENHIGH
STA ScreenClearAddPtr+2
SC_Reset:
LDA #0
SC_Loop:
ScreenClearAddPtr:
STA $FFFF
INC ScreenClearAddPtr+1
BNE SC_Loop
LDA ScreenClearAddPtr+2
CLC
ADC #1
STA ScreenClearAddPtr+2
CMP #$80
BNE SC_Reset
RTS
;-------------------------------------------------------------------------------
; End of ScreenFunctionality
;-------------------------------------------------------------------------------