Switched from raw input to low-level keyboard hook, with -W/--raw to optionally re-enable raw input (needed to debug, so the hook doesn't cause GDB to make system input unusably slow), fixes #4399.

src/device/keyboard.c

@@ -29,7 +29,9 @@
 
 #include "cpu.h"
 
-int keyboard_scan;
+uint16_t     scancode_map[768] = { 0 };
+
+int          keyboard_scan;
 
 #ifdef _WIN32
 /* Windows: F8+F12 */
@@ -386,3 +388,22 @@ keyboard_ismsexit(void)
         return ((recv_key_ui[key_prefix_1_1] || recv_key_ui[key_prefix_1_2]) &&
                 (recv_key_ui[key_uncapture_1] || recv_key_ui[key_uncapture_2]));
 }
+
+/* This is so we can disambiguate scan codes that would otherwise conflict and get
+   passed on incorrectly. */
+uint16_t
+convert_scan_code(uint16_t scan_code)
+{
+    if ((scan_code & 0xff00) == 0xe000)
+        scan_code = (scan_code & 0xff) | 0x0100;
+
+    if (scan_code == 0xE11D)
+        scan_code = 0x0100;
+    /* E0 00 is sent by some USB keyboards for their special keys, as it is an
+       invalid scan code (it has no untranslated set 2 equivalent), we mark it
+       appropriately so it does not get passed through. */
+    else if ((scan_code > 0x01FF) || (scan_code == 0x0100))
+        scan_code = 0xFFFF;
+
+    return scan_code;
+}