137 lines
2.1 KiB
ArmAsm
137 lines
2.1 KiB
ArmAsm
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//
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// CHROUT routine - screen support (character output)
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//
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chrout_screen:
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jsr cursor_hide_if_visible
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lda SCHAR
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tax
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// All the PETSCII control codes are within $0x, $1x, $8x, $9x, remaining
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// ones are always printable characters; separate away control codes
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and #$60
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bne !+
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jmp chrout_screen_control
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!:
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txa
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// Literals - first convert PETSCII to screen code
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// Codes $C0-$DF become $40-$5F
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cmp #$E0
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bcs !+
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cmp #$C0
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bcc !+
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and #$7F
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jmp chrout_screen_literal // not high char
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!:
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// Range $20-$3F is unchanged
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cmp #$40
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bcc chrout_screen_literal // not high char
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// Unshifted letters and symbols from $40-$5F
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// all end up being -$40
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// (C64 PRG p376)
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// But anything >= $80 needs to be -$40
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// (C64 PRG p380-381)
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// And bit 7 should be cleared, only to be
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// set by reverse video
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sec
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sbc #$40
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// Fix shifted chars by adding $20 again
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cmp #$20
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bcc chrout_screen_literal // not high char
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cmp #$40
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bcs chrout_screen_literal // not high char
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clc
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adc #$20
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// FALLTROUGH
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chrout_screen_literal:
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// Write normal character on the screen
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tax // store screen code, we need .A for calculations
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// First we need offset from PNT in .Y, we can take it from PNTR (0-79)
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lda PNTR
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cmp #40
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bcc !+
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sec
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sbc #40
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!:
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tay
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// Put the character on the screen
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txa
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ora RVS // Computes Mapping the 64, page 38
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sta (PNT),y
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// Decrement number of chars waiting to be inserted
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lda INSRT
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beq !+
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dec INSRT
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!:
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// Toggle quote flag if required
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txa
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cmp #$22
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bne !+
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lda QTSW
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eor #$80
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sta QTSW
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!:
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// Set colour of the newly printed character
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lda COLOR
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sta (USER),y
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// Advance the column
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ldy PNTR
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iny
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sty PNTR
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// Scroll down (extend logical line) if needed
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cpy #40
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bne !+
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jsr screen_grow_logical_line
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ldy PNTR
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!:
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// If not the 80th character of the logical row, we are done
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cpy #80
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bcc chrout_screen_done
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// Advance to the next line
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lda #0
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sta PNTR
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jmp screen_advance_to_next_line
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chrout_screen_calc_lptr_done:
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jsr screen_calculate_PNT_USER
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// FALLTROUGH
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chrout_screen_done:
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jsr cursor_show_if_enabled
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jmp chrout_done_success
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