Routines
Prev: A479 Up: Map Next: A591
A4B0: Handler: User Input
Used by the routine at GameStart.
Handles keyboard input, tokenises commands and validates the vocabulary.
Reset the screen position to defaults.
Handler_UserInput A4B0 CALL PrintPrompt Call PrintPrompt.
A4B3 LD HL,$A109 HL=CommandBuffer.
Initialise the command buffer.
A4B6 LD B,$00 Initialise a letter counter in B.
A4B8 JR UserInput_Next Jump to UserInput_Next.
Main input loop - process each keypress.
UserInput_Loop A4BA INC HL Move to the next byte of the command buffer.
A4BB INC B Increment the letter counter by one.
UserInput_Next A4BC CALL Print_Cursor Call Print_Cursor.
A4BF CALL GetUserInput Call GetUserInput.
A4C2 CP $0C Jump to ValidateUserInput if "DELETE" was not pressed.
A4C4 JR NZ,ValidateUserInput
The user pressed "DELETE".
A4C6 XOR A Jump back to UserInput_Next if there hasn't been any input yet (nothing to delete).
A4C7 OR B
A4C8 JR Z,UserInput_Next
There is input which can be deleted, so action a delete!
A4CA EX DE,HL Temporarily stash the command buffer pointer in DE.
Print "SPACE BACKSPACE BACKSPACE SPACE BACKSPACE" to move the current print position on the screen to the previous character, and to delete the character present using a space.
A4CB LD HL,$A447 HL=Messaging_SpaceBackspaceBackspaceSpaceBackspace.
A4CE CALL PrintString Call PrintString.
Adjust the command buffer position and letter counter.
A4D1 EX DE,HL Restore the command buffer pointer from DE.
A4D2 DEC HL Decrease the command buffer pointer by one.
A4D3 DEC B Decrease the letter counter by one.
A4D4 JR UserInput_Next Jump to UserInput_Next.
Check which key the user pressed:
ValidateUserInput A4D6 LD C,A Jump to UserInput_WriteKeypress if "ENTER" was pressed.
A4D7 CP $0D
A4D9 JR Z,UserInput_WriteKeypress
A4DB CP $20 If the keypress was any other control key (the value being under 20 ASCII "SPACE"), it's not valid input so jump back to UserInput_Next.
A4DD JR C,UserInput_Next
A4DF CP $80 If the keypress was higher than 80 it's also not valid input so jump back to UserInput_Next.
A4E1 JR NC,UserInput_Next
Is the command buffer full?
A4E3 LD A,B Jump to UserInput_Next if the letter counter is 31 (so the buffer is full).
A4E4 CP $31
A4E6 JR Z,UserInput_Next
Writes the keypress into the command buffer and print it to the screen.
UserInput_WriteKeypress A4E8 LD A,C Write the user input key to *HL.
A4E9 LD (HL),A
A4EA CALL Print_UserInputToScreen Call Print_UserInputToScreen.
Did the user press "ENTER"?
A4ED LD A,C Jump to UserInput_Loop if "ENTER" was not pressed.
A4EE CP $0D
A4F0 JR NZ,UserInput_Loop
The player pressed "ENTER" so begin to process the user input.
Clear down the user input tokens.
A4F2 LD HL,$A13B HL=UserInput_Token_1.
A4F5 LD B,$0A Set a counter in B for all 0A user input tokens.
EmptyUserInputTokens_Loop A4F7 LD (HL),$FF Write a termination byte (FF) to *HL.
A4F9 INC HL Increment HL by one.
A4FA DJNZ EmptyUserInputTokens_Loop Decrease the user input tokens counter by one and loop back to EmptyUserInputTokens_Loop until all the tokens have been set to termination bytes (FF).
Set up pointers for the command buffer, the user input tokens and the count of the number of user input tokens.
A4FC LD HL,$A109 HL=CommandBuffer.
A4FF LD IX,$A13B IX=UserInput_Token_1.
A503 LD C,$0A Set a counter in C for the 0A user input tokens.
A505 JR EmptyFourLetterBuffer Jump to EmptyFourLetterBuffer.
Print "Give me a command!".
Handler_UserInput_0 A507 LD HL,$0001 HL=Messaging_GiveMeACommand.
A50A CALL PrintCompressedStringAndNewline Call PrintCompressedStringAndNewline.
A50D JP Handler_UserInput Jump to Handler_UserInput.
Handler_UserInput_1 A510 PUSH HL
A511 PUSH DE
A512 PUSH BC
A513 LD HL,($A443)
A516 LD DE,$A145
A519 LD BC,$0004
A51C LD A,($A445)
A51F CP C
A520 JR NC,Handler_UserInput_2
A522 LD C,A
Handler_UserInput_2 A523 LDIR
A525 POP BC
A526 POP DE
A527 POP HL
A528 PUSH HL
A529 LD HL,$9DD2
A52C LD ($A47F),HL
A52F CALL Handler_MatchItem
A532 LD HL,$B0ED
A535 LD ($A47F),HL
A538 POP HL
A539 JR C,EmptyFourLetterBuffer
A53B CALL Handler_MatchItem
A53E JR C,StoreTokenAndContinue
A540 LD HL,$0002
A543 CALL PrintCompressedStringAndNewline
A546 JP Handler_UserInput
StoreTokenAndContinue A549 LD (IX+$00),A
A54C INC IX
A54E DEC C
A54F JR Z,Handler_UserInput_9
EmptyFourLetterBuffer A551 PUSH HL
A552 PUSH BC
A553 LD HL,$A145
A556 LD B,$04
Handler_UserInput_3 A558 LD (HL),$20
A55A INC HL
A55B DJNZ Handler_UserInput_3
A55D POP BC
A55E POP HL
A55F PUSH DE
A560 JR Handler_UserInput_5
Handler_UserInput_4 A562 INC HL
Handler_UserInput_5 A563 LD A,(HL)
A564 CP $0D
A566 JR Z,Handler_UserInput_8
A568 CALL IsDelimiter
A56B JR Z,Handler_UserInput_4
A56D LD ($A443),HL
A570 LD DE,$0000
Handler_UserInput_6 A573 INC HL
A574 INC DE
A575 LD A,(HL)
A576 CP $0D
A578 JR Z,Handler_UserInput_7
A57A CALL IsDelimiter
A57D JR NZ,Handler_UserInput_6
Handler_UserInput_7 A57F LD ($A445),DE
A583 SCF
Handler_UserInput_8 A584 POP DE
A585 JP C,Handler_UserInput_1
Handler_UserInput_9 A588 LD A,($A13B)
A58B CP $FF
A58D JP Z,Handler_UserInput_0
A590 RET
View the equivalent code in;
Prev: A479 Up: Map Next: A591