From e38d1df8071fb877172c078ef80423c8138cfe52 Mon Sep 17 00:00:00 2001
From: Ry <ryanst755@gmail.com>
Date: Thu, 12 May 2022 17:23:01 -0700
Subject: [PATCH] monitor: Don't allow backspacing past the start of the prompt

---
 monitor/shell.asm | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/monitor/shell.asm b/monitor/shell.asm
index 453db0e..858aa1a 100644
--- a/monitor/shell.asm
+++ b/monitor/shell.asm
@@ -56,6 +56,10 @@ monitor_shell_key_down_event_enter:
     call print_string_to_monitor
     ret
 monitor_shell_key_down_event_backspace:
+    ; check if we are already at the start of the prompt
+    mov r1, [MONITOR_SHELL_TEXT_BUF_PTR]
+    cmp r1, MONITOR_SHELL_TEXT_BUF_BOTTOM
+    iflteq ret
     ; delete the last character from the screen, and pop the last character from the buffer
     mov r0, 8 ; backspace character
     call print_character_to_monitor