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https://github.com/Pecusx/scorch_src.git
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Pecusx
231 lines
4.5 KiB
NASM
231 lines
4.5 KiB
NASM
.IF *>0 ;this is a trick that prevents compiling this file alone
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; Basic hardware-dependent graphics routines.
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; -----------------------------------------
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.proc unPlot
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; plots a point and saves the plotted byte, reverts the previous plot.
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; -----------------------------------------
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ldx #0 ; only one pixel
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unPlotAfterX
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stx WhichUnPlot
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; first remake the oldie
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lda oldplotL,x
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sta oldplot
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lda oldplotH,x
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sta oldplot+1
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lda oldply,x
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tay
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lda oldora,x
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sta (oldplot),y
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; is it not out of the screen ????
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cpw ydraw #screenheight
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jcc CheckX
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mwa #0 ydraw
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CheckX
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cpw xdraw #screenwidth
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jcs EndOfUnPlot
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MakeUnPlot
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; let's count coordinates taken from xdraw and ydraw
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;xbyte = xbyte/8
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lda xdraw+1
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lsr
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lda xdraw
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ror ;just one bit over 256. Max screenwidth = 512!!!
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lsr
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lsr
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;---
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tay
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ldx WhichUnPlot
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tya
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sta oldply,x
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ldx ydraw
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lda linetableL,x
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sta xbyte
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sta oldplot
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lda linetableH,x
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sta xbyte+1
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sta oldplot+1
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lda xdraw
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and #$7
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tax
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lda color
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bne ClearUnPlot
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;plotting here
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lda (xbyte),y
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sta OldOraTemp
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ora bittable,x
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sta (xbyte),y
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bne ContinueUnPlot ; allways <>0
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ClearUnPlot
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lda (xbyte),y
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sta OldOraTemp
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and bittable2,x
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sta (xbyte),y
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ContinueUnPlot
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ldx WhichUnPlot
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lda OldOraTemp
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sta oldora,x
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lda oldplot
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sta oldplotL,x
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lda oldplot+1
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sta oldplotH,x
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; and now we must solve the problem of several plots
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; in one byte
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ldx #4
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ldy WhichUnPlot
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LetsCheckOverlapping
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cpx WhichUnPlot
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beq SkipThisPlot
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lda oldplotL,x
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cmp oldplotL,y
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bne NotTheSamePlot
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lda oldplotH,x
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cmp oldplotH,y
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bne NotTheSamePlot
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lda oldply,x
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cmp oldply,y
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bne NotTheSamePlot
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; the pixel is in the same byte so let's take correct contents
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lda oldora,x
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sta oldora,y
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NotTheSamePlot
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SkipThisPlot
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dex
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bpl LetsCheckOverlapping
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EndOfUnPlot
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rts
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.endp
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; -----------------------------------------
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.proc plot ;plot (xdraw, ydraw, color)
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; color == 1 --> put pixel
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; color == 0 --> erase pixel
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; this is one of the most important routines in the whole
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; game. If you are going to speed up the game, start with
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; plot - it is used by every single effect starting from explosions
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; through line drawing and small text output!!!
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;
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; Optimized by 0xF (Fox) THXXXX!!!
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; -----------------------------------------
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; is it not over the screen ???
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cpw ydraw #(screenheight+1); changed for one additional line. cpw ydraw #(screenheight-1)
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bcs unPlot.EndOfUnPlot ;nearest RTS
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CheckX02
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cpw xdraw #screenwidth
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bcs EndOfPlot
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MakePlot
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; let's calculate coordinates from xdraw and ydraw
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;xbyte = xbyte/8
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lda xdraw+1
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lsr
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lda xdraw
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ror ;just one bit over 256. Max screenwidth = 512!!!
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lsr
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lsr
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sta xbyte
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;---
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ldx ydraw
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ldy linetableL,x
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lda linetableH,x
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sta xbyte+1
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lda xdraw
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and #$7
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tax
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lda color
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bne ClearPlot
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lda (xbyte),y
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ora bittable,x
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sta (xbyte),y
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EndOfPlot
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rts
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ClearPlot
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lda (xbyte),y
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and bittable2,x
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sta (xbyte),y
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rts
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.endp
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; -----------------------------------------
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.proc point_plot
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; -----------------------------------------
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; checks state of the pixel (coordinates in xdraw and ydraw)
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; result is in A (zero or appropriate bit is set)
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; let's calculate coordinates from xdraw and ydraw
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;xbyte = xbyte/8
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lda xdraw+1
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lsr
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lda xdraw
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ror ;just one bit over 256. Max screenwidht = 512!!!
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lsr
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lsr
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sta xbyte
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;---
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ldx ydraw
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ldy linetableL,x
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lda linetableH,x
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sta xbyte+1
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lda xdraw
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and #$7
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tax
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lda (xbyte),y
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eor #$ff
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and bittable,x
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rts
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.endp
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;--------------------------------------------------
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.proc ClearScreen
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;--------------------------------------------------
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mwa #displayC64 temp
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ldy #0
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@ lda #$ff
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sta (temp),y
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inw temp
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cpw temp #displayC64+screenheight*screenBytes+1
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bne @-
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rts
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.endp
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;--------------------------------------------------
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.proc GenerateLineTable
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mwa #displayC64 temp
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mwa #linetableL temp2
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mwa #linetableH modify
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ldy #0
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@ lda temp
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sta (temp2),y
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lda temp+1
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sta (modify),y
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adw temp #40
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iny
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cpy #screenheight+1
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bne @-
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rts
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.endp
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;--------------------------------------------------
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.proc SetMainScreen
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SwitchVICBank(0)
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SetScreenMemory($2000)
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SetHiresBitmapMode ; Hires mode on
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rts
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.endp
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.ENDIF |