From 32c22fe34a80ced040c6497065e110e04db79db6 Mon Sep 17 00:00:00 2001
From: Yash Karandikar <nerdstep710@gmail.com>
Date: Thu, 16 Sep 2021 18:20:20 -0500
Subject: [PATCH] Don't move the cursor out of bounds

---
 src/interrupts.rs | 10 +++++++---
 src/vga_buffer.rs | 12 +++++++-----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/interrupts.rs b/src/interrupts.rs
index 2df9c36..a3fd5bb 100644
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -62,6 +62,8 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStac
                 DecodedKey::Unicode(character) => {
                     if character == '\u{8}' {
                         crate::vga_buffer::backspace();
+                    } else if character == '\u{9}' {
+                        print!("    ");
                     } else {
                         print!("{}", character)
                     }
@@ -79,9 +81,11 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStac
                             let mut writer = crate::vga_buffer::WRITER.lock();
                             let col = writer.column_position;
                             let row = crate::vga_buffer::BUFFER_HEIGHT - 1;
-
-                            crate::vga_buffer::move_cursor((col as u16) - 1, row as u16);
-                            writer.column_position -= 1;
+                            
+                            if col != 0 {
+                                crate::vga_buffer::move_cursor((col as u16) - 1, row as u16);
+                                writer.column_position -= 1;
+                            }
                         },
                         KeyCode::ArrowRight => {
                             let mut writer = crate::vga_buffer::WRITER.lock();
diff --git a/src/vga_buffer.rs b/src/vga_buffer.rs
index 68d4092..38435bc 100644
--- a/src/vga_buffer.rs
+++ b/src/vga_buffer.rs
@@ -157,11 +157,13 @@ pub fn backspace() {
     let row = BUFFER_HEIGHT - 1;
     let col = writer.column_position;
     let color_code = writer.color_code;
-    writer.buffer.chars[row][col - 1].write(ScreenChar {
-        ascii_character: b' ',
-        color_code
-    });
-    writer.column_position -= 1;
+    if col != 0 {
+        writer.buffer.chars[row][col - 1].write(ScreenChar {
+            ascii_character: b' ',
+            color_code
+        });
+        writer.column_position -= 1;
+    }
 }