Now that I better understand what Nut Berry keyboard ISR is doing, up…

…date the code and CHANGELOG comments. Also, copying your BIOS ISR instruction for instruction may seem clever but all it does is make sure it only works on your own dev machine, so do not do that

CHANGELOG

@@ -1,13 +1,10 @@
 Next:
   - Write PC-98 keyboard translation table (non-shifted) in ROM BIOS and set the
     keyboard translation table pointer in the BIOS data area for "Nut Berry".
-    This should allow keyboard input to work as long as you don't touch any
-    modifier keys (because the game will zero that pointer if you do because of
-    assumptions about the ROM BIOS), but keyboard input should work otherwise.
-    The "Nut Berry" game uses it's own entirely custom keyboard interrupt handler
-    instead of the BIOS (DOSBox-X provided) one and it makes quite a few assumptions
-    about where some tables are in the ROM BIOS. Time to pull out the PC-98 hardware
-    and do some more ROM BIOS examination. (joncampbell123).
+    This Nut Berry game also assumes lookup and translation tables exist at
+    specific locations in the ROM BIOS, so put those tables there. The shift
+    state table in BIOS has also been added, though at the moment, they all
+    reflect the normal unshifted state which shouldn't be a problem. (joncampbell123).
   - MegaZeux from the MS-DOS days had a 256-color tweakmode that worked on some
     popular SVGA chipsets of it's time though on others it does nothing but halve
     the display resolution of text mode. The basic idea is that it makes the VGA

src/ints/bios.cpp

@@ -3519,11 +3519,11 @@ static Bitu INT18_PC98_Handler(void) {
             IO_WriteB(0x43, 0x16);
             for (int i=0; i<0x20; i++) mem_writeb(0x502+i, 0);
             for (int i=0; i<0x13; i++) mem_writeb(0x528+i, 0);
-            mem_writew(0x522, 0x0e00);
+            mem_writew(0x522,(unsigned int)(Real2Phys(BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION) - 0xFD800));
             mem_writew(0x524, 0x0502);
             mem_writew(0x526, 0x0502);
-            mem_writew(0x5c6, 0x0e00);
-            mem_writew(0x5c8, 0xfd80);
+            mem_writew(0x5C6,(unsigned int)(Real2Phys(BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION) - 0xFD800));
+            mem_writew(0x5C8,0xFD80);
             break;
         case 0x04: /* Sense of key input state (キー入力状態のセンス) */
             reg_ah = mem_readb(0x52A + (unsigned int)(reg_al & 0x0Fu));
@@ -8224,6 +8224,8 @@ class BIOS:public Module_base{
 
             /* Set up the translation table poiner, which is relative to segment 0xFD80 */
             mem_writew(0x522,(unsigned int)(Real2Phys(BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION) - 0xFD800));
+            mem_writew(0x5C6,(unsigned int)(Real2Phys(BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION) - 0xFD800));
+            mem_writew(0x5C8,0xFD80);
         }
 
         if (bios_user_reset_vector_blob != 0 && !bios_user_reset_vector_blob_run) {
@@ -10051,7 +10053,7 @@ class BIOS:public Module_base{
 
 	if (IS_PC98_ARCH) {
 		/* Keyboard translation tables, must exist at segment 0xFD80:0x0E00 because PC-98 MS-DOS assumes it (it writes 0x522 itself on boot) */
-		BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION = PhysToReal416(ROMBIOS_GetMemory(0x80/*TODO: multiple tables eventually*/,"Keyboard translation tables",/*align*/1,0xFD800+0xE00));
+		BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION = PhysToReal416(ROMBIOS_GetMemory(0x80/*TODO: multiple tables eventually*/,"Keyboard translation tables",/*align*/1,0xFD800+0xB31));
 		BIOSKEY_PC98_Write_Tables();
 	}
 
@@ -10394,6 +10396,34 @@ class BIOS:public Module_base{
                 bo = 0xE8000;
                 phys_writeb(bo+0x00,(uint8_t)0xEB);                       // JMP $+2 (to next instruction)
                 phys_writeb(bo+0x01,(uint8_t)0x00);
+
+                /* "Nut Berry" expects a 8-byte lookup table for [AL&7] -> 1 << (AL&7) at 0xFD80:0x0E3C so it's
+                 * custom keyboard interrupt handler can update the keyboard status bitmap in the BIOS data area.
+                 * I don't know if the game even uses it. On a BIOS.ROM image I have, and on real hardware, there
+                 * is clearly that table but at slightly different addresses (One PC-9821 laptop has it at
+                 * 0xFD80:0x0E45) which means whether the game uses it or not the bitmap may have random bits set
+                 * when you exit to DOS.
+                 *
+                 * Assuming no other game does this, this fixed address should be fine.
+                 *
+                 * NOTE: After disassembling the IRQ1 handler on a real PC-9821 laptop, I noticed this game's
+                 *       custom ISR bears a strong resemblance to it. In fact, you might say it's an exact instruction
+                 *       for instruction copy of the ISR, except that the table addresses in ROM are slightly different.
+                 *       Ha. Theoretically then, that means we could also get this game to work fully properly by patching
+                 *       it not to hook the keyboard interrupt at all! */
+                for (unsigned int i=0;i < 8;i++) phys_writeb(0xFD800+0xE3C+i,1u << i);
+
+                /* "Nut Berry" also assumes shift state table offsets (for all 16 possible combinations) exist
+                 * at 0xFD80:0x0E28. Once again, this means it will not work properly on anything other than the dev's
+                 * machine because on a real PC-9821 laptop used for testing, the table offset is slightly different
+                 * (0xE31 instead of 0xE28). The table mentioned here is used to update the 0x522 offset WORD in the
+                 * BIOS data area to reflect the translation table in effect based on the shift key status, so if you
+                 * misread the table you end up pointing it at junk and then keyboard input doesn't work anymore. */
+                // FIXME: This implementation does not yet implement all tables!
+                // NTS: On a real PC-9821 laptop, the table is apparently 10 entries long. If BDA byte 0x53A is less than
+                //      8 then it's just a simple lookup. If BDA byte 0x53A has bit 4 set, then use the 8th entry, and
+                //      if bit 4 and 3 are set, use the 9th entry.
+                for (unsigned int i=0;i < 10;i++) phys_writew(0xFD800+0xE28+(i*2),(unsigned int)(Real2Phys(BIOS_PC98_KEYBOARD_TRANSLATION_LOCATION) - 0xFD800));
             }
 	    else {
 		    if (ibm_rom_basic_size == 0) {