Add cursor support from kernel

Author: Ian Seyler

src/monitor.asm

@@ -1068,21 +1068,22 @@ string_to_int_invalid:
 ui_input:
 	push rdi
 	push rdx			; Counter to keep track of max accepted characters
+	push rbx
 	push rax
 
 	mov rdx, rcx			; Max chars to accept
+	xor ebx, ebx			; Cursor position
 	xor ecx, ecx			; Offset from start
 
 ui_input_more:
-	mov al, '_'			; Cursor character
-	call output_char		; Output the cursor
-	mov al, 0x03			; Decrement cursor
-	call output_char		; Output the cursor
-ui_input_halt:
 	hlt				; Halt until an interrupt is received
 	call [b_input]			; Returns the character entered. 0 if there was none
-	jz ui_input_halt		; If there was no character then halt until an interrupt is received
+	jz ui_input_more		; If there was no character then halt until an interrupt is received
 ui_input_process:
+	cmp al, 0x02
+	je ui_input_inc_cursor
+	cmp al, 0x03
+	je ui_input_dec_cursor
 	cmp al, 0x1C			; If Enter key pressed, finish
 	je ui_input_done
 	cmp al, 0x0E			; Backspace
@@ -1094,31 +1095,47 @@ ui_input_process:
 	cmp rcx, rdx			; Check if we have reached the max number of chars
 	je ui_input_more		; Jump if we have (should beep as well)
 	stosb				; Store AL at RDI and increment RDI by 1
+	inc ebx
 	inc rcx				; Increment the counter
 	call output_char		; Display char
 	jmp ui_input_more
 
 ui_input_backspace:
-	test rcx, rcx			; backspace at the beginning? get a new char
+	test ecx, ecx			; backspace at the beginning? get a new char
 	jz ui_input_more
-	mov al, ' '
-	call output_char		; Output backspace as a character
 	mov al, 0x03			; Decrement cursor
 	call output_char		; Output the cursor
+	mov al, ' '
+	call output_char		; Output backspace as a character
 	mov al, 0x03			; Decrement cursor
 	call output_char		; Output the cursor
 	dec rdi				; go back one in the string
 	mov byte [rdi], 0x00		; NULL out the char
 	dec rcx				; decrement the counter by one
 	jmp ui_input_more
 
+ui_input_inc_cursor:
+	cmp ebx, ecx
+	je ui_input_more
+	call output_char		; Output the cursor
+	inc ebx
+	jmp ui_input_more
+
+ui_input_dec_cursor:
+	test ebx, ebx			; backspace at the beginning? get a new char
+	jz ui_input_more
+	call output_char		; Output the cursor
+	dec ebx
+	jmp ui_input_more
+
 ui_input_done:
 	xor al, al
 	stosb				; We NULL terminate the string
 	mov al, ' '
 	call output_char		; Overwrite the cursor
 
 	pop rax
+	pop rbx
 	pop rdx
 	pop rdi
 	ret