Routines
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59887: Blit Display Buffer Row
Used by the routine at Blit_DisplayBuffer.
Blit one display-buffer tile to the screen. The graphic-set index selects a base from Table_GraphicSetAddresses; the tile index × 8 is added to that base Attribute bit 7 selects the mirrored blit at Blit_DisplayBufferRowLoop (via BitmapMirrorLookup).
Write the attribute and resolve the graphic-set tile address.
Blit_DisplayBufferRow 59887 SET 6,A Force bright on the attribute in A and write it through IX.
59889 LD (IX+0),A
59892 LD L,B Keep the tile index in HL (high byte cleared).
59893 XOR A
59894 LD B,A
59895 LD H,A
59896 ADD A,C Double the graphic-set index into BC as a word offset.
59897 ADD A,C
59898 LD C,A
59899 PUSH HL
59900 LD HL,29451 Point HL at Table_GraphicSetAddresses, add the set offset, and fetch the set base into BC.
59903 ADD HL,BC
59904 LD C,(HL)
59905 INC HL
59906 LD B,(HL)
59907 POP HL Restore the tile index, multiply it by 8, and add the set base to get the bitmap address.
59908 ADD HL,HL
59909 ADD HL,HL
59910 ADD HL,HL
59911 ADD HL,BC
59912 EX DE,HL Keep the bitmap address in DE.
Convert the attribute address into a screen-bitmap address and blit.
59913 PUSH IX Copy IX to HL (using the stack).
59915 POP HL
59916 LD A,H Multiply the attribute high byte by 8.
59917 ADD A,A
59918 ADD A,A
59919 ADD A,A
59920 AND %01011011 Keep only the screen-bitmap high bits (mask 91).
59922 LD H,A Write the result to H and move the address into DE.
59923 EX DE,HL
59924 BIT 7,(IX+0) Is the mirror bit (bit 7) set on the attribute? If so, blit the mirrored tile at Blit_DisplayBufferRowLoop.
59928 JR NZ,Blit_DisplayBufferRowLoop
59930 LD B,8 There are 8 pixel rows in a tile.
Copy 8 pixel rows of an unmirrored tile into the screen bitmap.
Blit_DisplayBufferRow_CopyRows 59932 LD A,(HL) Copy one bitmap row to the screen and step to the next pixel row.
59933 LD (DE),A
59934 INC D
59935 INC HL
59936 DJNZ Blit_DisplayBufferRow_CopyRows
59938 RET Return.
Blit the tile with horizontal mirroring via BitmapMirrorLookup.
Blit_DisplayBufferRowLoop 59939 RES 7,(IX+0) Clear the mirror bit on the attribute at IX.
59943 LD B,8 There are 8 pixel rows in a tile.
Copy 8 pixel rows with horizontal mirroring via BitmapMirrorLookup.
Blit_DisplayBufferRowLoopB 59945 PUSH BC Fetch a bitmap byte, reverse it through BitmapMirrorLookup, write it to the screen, and step to the next pixel row.
59946 LD A,(HL)
59947 PUSH HL
59948 LD HL,29465
59951 LD C,A
59952 LD B,0
59954 ADD HL,BC
59955 LD A,(HL)
59956 POP HL
59957 LD (DE),A
59958 INC D
59959 INC HL
59960 POP BC
59961 DJNZ Blit_DisplayBufferRowLoopB
59963 RET Return.
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