handle commands coming from virtual keyboard

messages.asm

@@ -63,9 +63,14 @@ int 0x10
 
 .loop:
 	;; read a character, ASCII in al
-	mov ah, 0x00	; Read character
+	mov ah, 0x0		; Read character
 	int 0x16
 
+	;; a null character will be sent before every command from the virtual keyboard
+	;; so if a null is detected go to the virtual_kbd_loop instead
+	cmp al, 0x0		; null
+	je .virtual_kbd_loop_init
+
 	mov ah, 0x1
 	mov dx, 0x0
 	int 0x14
@@ -81,20 +86,43 @@ int 0x10
 
 	jmp nonewline	; all other characters
 
+.nl_reset_state:
+	mov byte[is_from_virtual_kbd], 0x0	; reset state variable
 .nl:
 	call newline
 	jmp .loop
 
+.virtual_kbd_loop_init:
+	mov byte[is_from_virtual_kbd], 0x1	; update state variable
+.virtual_kbd_loop:
+	;; read a character, ASCII in al
+	mov ah, 0x0
+	int 0x16
+
+	cmp al, 0x08 	; backspace
+	je change_color_mode
+
+	cmp al, 0x1b 	; esc
+	je beep
+
+	;; an enter character signifies the end of a command
+	;; so a newline should get printed and then the program should resume
+	;; from the main .loop again
+	cmp al, 0xD		; enter
+	je .nl_reset_state
+
+	jmp nonewline	; all other characters
+
 ;; Update the color_mode variable with a byte from the keyboard
 ;;
 ;; CLOBBERS
 ;; - ax
 ;; - bl
 change_color_mode:
-	call readbyte		; get byte from keyboard (in al)
+	call readbyte			; get byte from keyboard (in al)
 	mov [color_mode], al	; store byte in color_mode variable
 
-	jmp start.loop
+	jmp compare_virtual_and_jump
 
 ;; Simulates going to a new line
 ;;
@@ -181,7 +209,7 @@ beep:
 	and     al, 11111100b	; Clear bits 1 and 0 (disable speaker, clear channel select)
 	out     61h, al         ; Send new value
 
-	jmp start.loop
+	jmp compare_virtual_and_jump
 
 ;; Handles all other characters by writing them to the screen
 ;;
@@ -212,7 +240,7 @@ nonewline:
 .eol:
 	call newline
 
-	jmp start.loop
+	jmp compare_virtual_and_jump
 
 .noeol:
 	;; Move cursor forward
@@ -220,6 +248,15 @@ nonewline:
 	mov ah, 0x02	; set cursor position, dh (row) already set, dl (col) updated on prev line
 	int 0x10
 
+	jmp compare_virtual_and_jump
+
+;; Compares the is_from_virtual_kbd state variable to 1 to check if the command
+;; came from the virtual keyboard
+;; if it did, jump to the virtual keyboard loop
+;; if it didn't, jump to the main loop
+compare_virtual_and_jump:
+	cmp byte[is_from_virtual_kbd], 0x1
+	je start.virtual_kbd_loop
 	jmp start.loop
 
 ;; Reads two characters from the keyboard buffer and converts them into a single byte
@@ -273,6 +310,8 @@ read_duration:
 
 ;; Variable to store color mode information for writing to the screen
 color_mode: db 0x02
+;; State variable for detecting whether keystrokes are virtual or real
+is_from_virtual_kbd: db 0x0
 
 ;; Magic number must be in the last 2 bytes of the sector so
 ;; fill the binary with zeroes until it is 510 bytes in size