Routines
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BF73: Handler: User Input
Used by the routines at Handler_UnknownWord and GameLoop.
Read a line of text, then turn it into vocabulary tokens.
Reset the cursor to the top of the text window.
Handler_UserInput BF73 CALL SetDefaultScreenPosition Call SetDefaultScreenPosition to park the cursor at the top of the text.
Clear the command buffer.
BF76 LD HL,$BB04 Start at the command buffer (InputBuffer).
BF79 LD A,$20 Prepare a space (20) and a counter of 32 bytes.
BF7B LD B,$32
UserInput_Clear BF7D LD (HL),A Write spaces through the whole command buffer.
BF7E INC HL
BF7F DJNZ UserInput_Clear
Print the ">" prompt.
BF81 CALL PrintInputPrompt Call PrintInputPrompt.
Collect keypresses.
BF84 LD HL,$BB04 Start again at the beginning of the command.
Wait for the next key.
UserInput_Loop BF87 CALL GetUserInput Call GetUserInput.
DELETE rubs out a character. ENTER finishes the line. Any other control key is ignored.
BF8A CP $0C Jump to UserInput_Delete if DELETE was pressed.
BF8C JR Z,UserInput_Delete
BF8E CP $0D Jump to UserInput_Enter if ENTER was pressed.
BF90 JR Z,UserInput_Enter
BF92 CP $20 Jump back to UserInput_Loop when the key is below SPACE.
BF94 JR C,UserInput_Loop
Is the command buffer full?
BF96 EX DE,HL Jump back to UserInput_Loop once the pointer has reached the sentinel at BB35.
BF97 LD HL,$BB35
BF9A AND A
BF9B SBC HL,DE
BF9D EX DE,HL
BF9E JR Z,UserInput_Loop
The key is valid, so store it and print it.
BFA0 LD (HL),A Write the key into the command buffer.
BFA1 CALL SwitchToNormalScreenOutput Call SwitchToNormalScreenOutput to select the screen channel.
BFA4 CALL PrintCharacter Call PrintCharacter to echo the key.
BFA7 INC HL Advance to the next space in the buffer.
BFA8 JR UserInput_Loop Jump back to UserInput_Loop for the next key.
The player pressed DELETE.
UserInput_Delete BFAA EX DE,HL Jump back to UserInput_Loop when the buffer is still empty.
BFAB LD HL,$BB04
BFAE AND A
BFAF SBC HL,DE
BFB1 EX DE,HL
BFB2 JR Z,UserInput_Loop
Rub the previous character off the screen.
BFB4 PUSH HL Keep the buffer pointer safe.
BFB5 LD HL,$BB58 Print " ".
BFB8 CALL PrintString
BFBB POP HL Restore the buffer pointer from the stack.
BFBC DEC HL Step back one character and blank it.
BFBD LD (HL),$20
BFBF JR UserInput_Loop Jump back to UserInput_Loop for the next key.
The player pressed ENTER, so close the command and clear the tokens.
UserInput_Enter BFC1 LD (HL),A Store ENTER as the end of the command.
BFC2 CALL SwitchToNormalScreenOutput Call SwitchToNormalScreenOutput to select the screen channel.
BFC5 CALL PrintCharacter Call PrintCharacter to echo ENTER.
BFC8 LD HL,$BB36 Start at the token buffer (BB36) and prepare the empty marker FF.
BFCB LD A,$FF
BFCD LD B,$0A
UserInput_ClearTokens BFCF LD (HL),A Write FF into each of the 0A token slots.
BFD0 INC HL
BFD1 DJNZ UserInput_ClearTokens
BFD3 LD HL,$BB04 Start at the command and allow 0A words, then fall into the parser.
BFD6 LD C,$0A
View the equivalent code in;
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