Routines
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9FB4: Draws a character (to buffer or screen?)
Used by the routine at 9F99.
Input
A Character to draw (ASCII)
A' Rendering type (double height, invert, etc.)
HL ...
DE Screen address
Output
HL ...
DE Screen address moved to next column
draw_char 9FB4 SUB $20 If it's not a space character, goto dc_not_space with A reduced
9FB6 JR NZ,dc_not_space
It's a space
9FB8 INC E Move screen address to the next column
9FB9 EXX
9FBA INC L <move something else that's banked>
9FBB EXX
9FBC RET Return
Map ASCII to glyph IDs
dc_not_space 9FBD LD C,$12 Offset = 18
9FBF CP $21 Jump if 'A' or above
9FC1 JR NC,dc_have_range
9FC3 LD C,$0B Offset = 11
9FC5 CP $10 Jump if '0' or above
9FC7 JR NC,dc_have_range
9FC9 LD C,$00 Glyph ID = 0
9FCB DEC A Jump if '!'
9FCC JR Z,dc_have_single
9FCE INC C Glyph ID = 1
9FCF SUB $07 Jump if '('
9FD1 JR Z,dc_have_single
9FD3 INC C Glyph ID = 2
9FD4 DEC A Jump if ')'
9FD5 JR Z,dc_have_single
9FD7 INC C Glyph ID = 3
9FD8 SUB $03 Jump if ','
9FDA JR Z,dc_have_single
9FDC INC C Glyph ID = 4
9FDD JR dc_have_single Anything else is '.'
A is an ASCII character - 32
dc_have_range 9FDF SUB C Convert (ASCII - 32) to glyph ID. C = A - Offset
9FE0 LD C,A
C is a glyph ID
dc_have_single 9FE1 LD A,C Multiply the glyph ID by 7
9FE2 RLCA
9FE3 LD B,A
9FE4 RLCA
9FE5 ADD A,B
9FE6 ADD A,C
9FE7 LD B,$00
9FE9 RL B Add in the carry
9FEB LD C,A BC is now the byte offset
9FEC LD HL,$A27A Point HL at 8x7 font
9FEF ADD HL,BC Point to glyph data
9FF0 EX AF,AF' Get type in C (passed in A' on entry)
9FF1 LD C,A
9FF2 EX AF,AF'
9FF3 DEC C If 1 then jump draw_char_3
9FF4 JP Z,draw_char_3
9FF7 DEC C If 2 then jump draw_char_2
9FF8 JP Z,draw_char_2
9FFB DEC C
9FFC JR Z,dc_double_height_glyph If 3 then jump dc_double_height_glyph -- double height
9FFE DEC C
9FFF JR Z,draw_char_1 If 4 then jump draw_char_1 -- single height inverted
A001 DEC C
A002 JR Z,draw_char_0 If 5 then jump draw_char_0 -- double height + inverted
Otherwise it's type 6
A004 PUSH DE
A005 LD B,$04 B = 4
dc_loop1 A007 LD A,(HL) A = *HL
A008 LD (DE),A *DE = A
A009 INC D Move to next row
A00A LD (DE),A *DE = A
A00B INC D Move to next row
A00C INC HL Move to next glyph row
A00D DJNZ dc_loop1 While iterations remain, goto loop1
A00F LD A,D D -= 8
A010 SUB $08
A012 LD D,A
A013 LD A,E E += 32
A014 ADD A,$20
A016 LD E,A
A017 LD B,$03 B = 3
dc_loop2 A019 LD A,(HL) A = *HL
A01A LD (DE),A *DE = A
A01B INC D Move to next row
A01C LD (DE),A *DE = A
A01D INC D Move to next row
A01E INC HL Move to next glyph row
A01F DJNZ dc_loop2 While iterations remain, goto loop2
A021 JR dc_a074
draw_char_0 A023 PUSH DE
A024 LD B,$07 B = 7
dc_loop3 A026 LD A,(HL) A = ~*HL
A027 CPL
A028 LD (DE),A *DE = A
A029 INC D Move to next row
A02A LD (DE),A *DE = A
A02B INC D Move to next row
A02C INC HL Move to next glyph row
A02D DJNZ dc_loop3 While iterations remain, goto loop3
A02F JR dc_a074
draw_char_1 A031 PUSH DE
A032 LD B,$07 B = 7
dc_loop4 A034 LD A,(HL) *DE = ~*HL
A035 CPL
A036 LD (DE),A
A037 INC HL Move to next glyph row
A038 INC D Move to next row
A039 DJNZ dc_loop4 While iterations remain, goto loop4
A03B JR dc_a0a4
Plots double-height glyphs. DE->screen HL->glyph def
dc_double_height_glyph A03D PUSH DE
A03E XOR A *DE = 0
A03F LD (DE),A
A040 INC D D++
A041 LD A,(HL) *DE = *HL
A042 LD (DE),A
A043 INC D D++ -- next row
A044 LDI
A046 DEC E E--
A047 INC D D++
A048 LD A,(HL) Repeat six times
A049 LD (DE),A
A04A INC D
A04B LDI
A04D DEC E
A04E INC D
A04F LD A,(HL)
A050 LD (DE),A
A051 INC D
A052 LDI
A054 DEC E
A055 INC D
A056 LD A,(HL)
A057 LD (DE),A
A058 INC D
A059 LDI
A05B DEC E
A05C INC D
A05D LD A,(HL)
A05E LD (DE),A
A05F INC D
A060 LDI
A062 DEC E
A063 INC D
A064 LD A,(HL)
A065 LD (DE),A
A066 INC D
A067 LDI
A069 DEC E
A06A INC D
A06B LD A,(HL)
A06C LD (DE),A
A06D INC D
A06E LDI
A070 DEC E
A071 INC D
A072 XOR A A = 0
A073 LD (DE),A *DE = A
dc_a074 A074 POP DE
A075 INC E E++
A076 EXX
A077 PUSH HL
A078 LD A,(HL) *HL |= C
A079 OR C
A07A LD (HL),A
A07B ADD HL,DE HL += DE
A07C LD A,(HL) *HL |= C
A07D OR C
A07E LD (HL),A
A07F POP HL
A080 INC L L++
A081 EXX
A082 RET Return
draw_char_2 A083 PUSH DE
A084 XOR A A = 0
A085 LD (DE),A *DE = A
A086 INC D D++
A087 LDI
A089 DEC E E--
A08A INC D D++
A08B LDI
A08D DEC E E--
A08E INC D D++
A08F LDI
A091 DEC E E--
A092 INC D D++
A093 LDI
A095 DEC E E--
A096 INC D D++
A097 LDI
A099 DEC E E--
A09A INC D D++
A09B LDI
A09D DEC E E--
A09E INC D D++
A09F LDI
A0A1 DEC E E--
A0A2 INC D D++
A0A3 LD (DE),A *DE = A
dc_a0a4 A0A4 POP DE
A0A5 INC E E++
A0A6 EXX
A0A7 LD A,(HL) *HL |= C
A0A8 OR C
A0A9 LD (HL),A
A0AA INC L L++
A0AB EXX
A0AC RET Return
draw_char_3 A0AD PUSH DE Save screen pointer
A0AE LD B,$07 7 iterations/rows
dc_loop_a0b0 A0B0 LD A,(HL) Transfer a byte
A0B1 LD (DE),A
A0B2 INC D Move to next scanline (Y0++)
A0B3 INC HL Move to next row of glyph data
A0B4 LD A,D Did we rollover?
A0B5 AND $07
A0B7 JR NZ,draw_char_4 If no rollover goto loop
A0B9 LD A,D Undo rollover
A0BA SUB $08
A0BC LD D,A
A0BD LD A,E Y3++
A0BE ADD A,$20
A0C0 LD E,A
A0C1 JR NC,draw_char_4 If no rollover goto loop
A0C3 LD A,D There was rollover, so move it to Y6
A0C4 ADD A,$08
A0C6 LD D,A
draw_char_4 A0C7 DJNZ dc_loop_a0b0 Loop until we've done 7 lines
A0C9 POP DE Restore screen pointer
A0CA INC E Move to next column
A0CB RET Return
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