emailler/client/inc/menu.i

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;REQUIRES KEYCODES TO BE DEFINED
OPTIONS_PER_PAGE = $10
.bss
number_of_options: .res 2
current_option: .res 2
temp_option_counter: .res 2
first_option_this_page: .res 2
options_shown_this_page: .res 1
options_table_pointer: .res 2
jump_to_prefix: .res 1
last_page_flag: .res 1
get_current_byte: .res 4
.code
;on entry, AX should point to the list of null terminated option strings to be selected from
;on exit, AX points to the selected string
select_option_from_menu:
stax options_table_pointer
stax get_current_byte+1
;set the 'LDA' and RTS' opcodes for the 'get current byte' subroutine, which is self-modified-code, hence must be located in RAM not ROM
lda #$ad ;opcode for LDA absolute
sta get_current_byte
lda #$60 ;opcode for RTS
sta get_current_byte+3
lda #0
sta current_option
sta current_option+1
sta number_of_options
sta number_of_options+1
;count the number of options. this is done by scanning till we find a double zero, incrementing the count on each single zero
@count_strings:
jsr @skip_past_next_null_byte
inc number_of_options
bne :+
inc number_of_options+1
:
jsr get_current_byte
bne @count_strings
jmp @display_first_page_of_options
@skip_past_next_null_byte:
jsr @move_to_next_byte
jsr get_current_byte
bne @skip_past_next_null_byte
jsr @move_to_next_byte
rts
@move_to_next_byte:
inc get_current_byte+1
bne :+
inc get_current_byte+2
:
rts
;move the ptr along till it's pointing at the whatever is the value of current_option
@move_to_current_option:
ldax options_table_pointer
stax get_current_byte+1
lda #0
sta temp_option_counter
sta temp_option_counter+1
@skip_over_strings:
lda temp_option_counter
cmp current_option
bne @not_at_current_option
lda temp_option_counter+1
cmp current_option+1
bne @not_at_current_option
rts
@not_at_current_option:
jsr @skip_past_next_null_byte
inc temp_option_counter
bne :+
inc temp_option_counter+1
:
jmp @skip_over_strings
@display_first_page_of_options:
lda #0
sta first_option_this_page
sta first_option_this_page+1
@print_current_page:
lda first_option_this_page
sta current_option
lda first_option_this_page+1
sta current_option+1
lda #0
sta last_page_flag
jsr @move_to_current_option
jsr cls
ldax #select_from_following_options
jsr print
; lda #'('
; jsr print_a
; lda #'$'
; jsr print_a
; lda first_option_this_page+1
; jsr print_hex
; lda first_option_this_page
; jsr print_hex
; lda #'/'
; jsr print_a
; lda #'$'
; jsr print_a
; lda number_of_options+1
; jsr print_hex
; lda number_of_options
; jsr print_hex
; lda #')'
; jsr print_a
; jsr print_cr
jsr print_cr
lda #0
sta options_shown_this_page
@print_loop:
lda options_shown_this_page
clc
adc #'A'
jsr print_a
lda #')'
jsr print_a
lda #' '
jsr print_a
; lda get_current_byte+2
; jsr print_hex
; lda get_current_byte+1
; jsr print_hex
lda get_current_byte+1
ldx get_current_byte+2
jsr print
jsr print_cr
jsr @skip_past_next_null_byte
inc current_option
bne :+
inc current_option+1
:
lda current_option
cmp number_of_options
bne :+
lda current_option+1
cmp number_of_options+1
bne :+
inc last_page_flag
jmp @print_instructions_and_get_keypress
:
inc options_shown_this_page
lda options_shown_this_page
cmp #OPTIONS_PER_PAGE
beq @print_instructions_and_get_keypress
jmp @print_loop
@jump_to:
jsr print_cr
ldax #jump_to_prompt
jsr print
lda #'?'
jsr get_key
ora #$80 ;set the high bit
sta jump_to_prefix
ldax options_table_pointer
stax get_current_byte+1
lda #0
sta current_option
sta current_option+1
@check_if_at_jump_to_prefix:
jsr get_current_byte
ora #$80 ;set high bit
cmp jump_to_prefix
beq @at_prefix
jsr @skip_past_next_null_byte
inc current_option
bne :+
inc current_option+1
:
jsr get_current_byte
bne @check_if_at_jump_to_prefix
jsr beep ;if we got to the end of the options table without finding the char we want, then sound a beep
jmp @jump_to_finished
@at_prefix:
lda current_option
sta first_option_this_page
lda current_option+1
sta first_option_this_page+1
@jump_to_finished:
jmp @print_current_page
@print_instructions_and_get_keypress:
lda number_of_options+1
bne @navigation_instructions
lda number_of_options
cmp #OPTIONS_PER_PAGE
bcc :+
@navigation_instructions:
ldax #navigation_instructions
jsr print
:
@get_keypress:
lda #'?'
jsr get_key
; jsr print_hex
; @fixme:
; jmp @fixme
cmp #KEYCODE_SLASH
beq @jump_to
cmp #KEYCODE_RIGHT
beq @forward_one_page
cmp #KEYCODE_DOWN
beq @forward_one_page
cmp #KEYCODE_UP
beq @back_one_page
cmp #KEYCODE_LEFT
beq @back_one_page
ora #$e0 ;make it a lower case letter with high bit set
sec
sbc #$e1
bcc @get_keypress ;if we have underflowed, it wasn't a valid option
cmp #OPTIONS_PER_PAGE-1
beq @got_valid_option
bpl @get_keypress ;if we have underflowed, it wasn't a valid option
@got_valid_option:
clc
adc first_option_this_page
sta current_option
lda #0
adc first_option_this_page+1
sta current_option+1
jsr @move_to_current_option
ldax get_current_byte+1
rts
@forward_one_page:
clc
lda last_page_flag
beq :+
@back_to_first_page:
jmp @display_first_page_of_options
:
lda first_option_this_page
adc #OPTIONS_PER_PAGE
sta first_option_this_page
bcc :+
inc first_option_this_page+1
:
jmp @print_current_page
@back_one_page:
sec
lda first_option_this_page
sbc #OPTIONS_PER_PAGE
sta first_option_this_page
lda first_option_this_page+1
sbc #0
sta first_option_this_page+1
bmi @show_last_page_of_options
jmp @print_current_page
@show_last_page_of_options:
sec
lda number_of_options
sbc #OPTIONS_PER_PAGE
sta first_option_this_page
lda number_of_options+1
sbc #0
sta first_option_this_page+1
bmi @back_to_first_page
jmp @print_current_page
.rodata
select_from_following_options: .byte "SELECT ONE OF THE FOLLOWING OPTIONS:",13,0
navigation_instructions: .byte 13,"ARROW KEYS NAVIGATE BETWEEN MENU PAGES",13
.byte "/ TO JUMP ",13
.byte 0
jump_to_prompt: .byte "JUMP TO:",0