Kernel: Allow backspace '\b' to be remapped

Previously, one could put '\b' in a keymap, but in non-Terminal
applications, it would just insert a literal '\b' character instead of
behaving like backspace. This patch modifes
`visible_code_point_to_key_code` to include backspace, as well as
renaming it to `code_point_to_key_code` since '\b' is not a visible
character. Additionally, `KeyboardDevice::key_state_changed` has been
rearranged to apply the user's keymap before checking for things like
caps lock.

Kernel/API/KeyCode.h

@@ -168,7 +168,7 @@ inline const char* key_code_to_string(KeyCode key)
     }
 }
 
-inline KeyCode visible_code_point_to_key_code(u32 code_point)
+inline KeyCode code_point_to_key_code(u32 code_point)
 {
     switch (code_point) {
 #define MATCH_ALPHA(letter) \
@@ -250,6 +250,7 @@ inline KeyCode visible_code_point_to_key_code(u32 code_point)
         MATCH_KEY(Backtick, '`')
         MATCH_KEY(Space, ' ')
         MATCH_KEY(Tab, '\t')
+        MATCH_KEY(Backspace, '\b')
 #undef MATCH_KEY
 
     default:

Kernel/Devices/HID/KeyboardDevice.cpp

@@ -228,15 +228,6 @@ void KeyboardDevice::key_state_changed(u8 scan_code, bool pressed)
         }
     }
 
-    if (!g_caps_lock_remapped_to_ctrl && key == Key_CapsLock && pressed)
-        m_caps_lock_on = !m_caps_lock_on;
-
-    if (g_caps_lock_remapped_to_ctrl && key == Key_CapsLock)
-        m_caps_lock_to_ctrl_pressed = pressed;
-
-    if (g_caps_lock_remapped_to_ctrl)
-        update_modifier(Mod_Ctrl, m_caps_lock_to_ctrl_pressed);
-
     Event event;
     event.key = key;
     event.scancode = m_has_e0_prefix ? 0xe000 + scan_code : scan_code;
@@ -246,9 +237,20 @@ void KeyboardDevice::key_state_changed(u8 scan_code, bool pressed)
     event.code_point = HIDManagement::the().character_map().get_char(event);
 
     // If using a non-QWERTY layout, event.key needs to be updated to be the same as event.code_point
-    KeyCode mapped_key = visible_code_point_to_key_code(event.code_point);
-    if (mapped_key != KeyCode::Key_Invalid)
+    KeyCode mapped_key = code_point_to_key_code(event.code_point);
+    if (mapped_key != KeyCode::Key_Invalid) {
         event.key = mapped_key;
+        key = mapped_key;
+    }
+
+    if (!g_caps_lock_remapped_to_ctrl && key == Key_CapsLock && pressed)
+        m_caps_lock_on = !m_caps_lock_on;
+
+    if (g_caps_lock_remapped_to_ctrl && key == Key_CapsLock)
+        m_caps_lock_to_ctrl_pressed = pressed;
+
+    if (g_caps_lock_remapped_to_ctrl)
+        update_modifier(Mod_Ctrl, m_caps_lock_to_ctrl_pressed);
 
     if (pressed)
         event.flags |= Is_Press;