From c3d15ef36d183cb54df75466de5bb26fd38ce8d8 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Sat, 22 Mar 2025 19:45:32 +0100
Subject: [PATCH] EGA and JEGA: Implement some missing SuperEGA stuff and make
 the JEGA properly set the EGA type to SuperEGA, fixes #5370.

---
 src/include/86box/vid_ega.h |  1 +
 src/video/vid_ega.c         | 69 +++++++++++++++++++++++++++++++++----
 src/video/vid_jega.c        |  2 +-
 3 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/src/include/86box/vid_ega.h b/src/include/86box/vid_ega.h
index 082cb120a..5ff7d3871 100644
--- a/src/include/86box/vid_ega.h
+++ b/src/include/86box/vid_ega.h
@@ -178,6 +178,7 @@ extern uint8_t ega_in(uint16_t addr, void *priv);
 extern void    ega_poll(void *priv);
 extern void    ega_write(uint32_t addr, uint8_t val, void *priv);
 extern uint8_t ega_read(uint32_t addr, void *priv);
+extern void    ega_set_type(void *priv, uint32_t local);
 
 extern int firstline_draw;
 extern int lastline_draw;
diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index 781e9a9dd..18a53a127 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -67,6 +67,8 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
     ega_t  *ega = (ega_t *) priv;
     uint8_t o;
     uint8_t old;
+    uint8_t gdcmask  = (ega->actual_type == EGA_SUPEREGA) ? 0xff : 0x0f;
+    uint8_t crtcmask = (ega->actual_type == EGA_SUPEREGA) ? 0xff : 0x1f;
 
     if (((addr & 0xfff0) == 0x3d0 || (addr & 0xfff0) == 0x3b0) && !(ega->miscout & 1))
         addr ^= 0x60;
@@ -200,8 +202,8 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
             ega->gdcaddr = val;
             break;
         case 0x3cf:
-            ega->gdcreg[ega->gdcaddr & 15] = val;
-            switch (ega->gdcaddr & 15) {
+            ega->gdcreg[ega->gdcaddr & gdcmask] = val;
+            switch (ega->gdcaddr & gdcmask) {
                 case 2:
                     ega->colourcompare = val;
                     break;
@@ -238,6 +240,19 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
                     ega->colournocare = val;
                     break;
 
+                case 0xf8:
+                    ega->la = val;
+                    break;
+                case 0xf9:
+                    ega->lb = val;
+                    break;
+                case 0xfa:
+                    ega->lc = val;
+                    break;
+                case 0xfb:
+                    ega->ld = val;
+                    break;
+
                 default:
                     break;
             }
@@ -247,7 +262,7 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
             if (ega->chipset)
                 ega->crtcreg = val & 0x3f;
             else
-                ega->crtcreg = val & 0x1f;
+                ega->crtcreg = val & crtcmask;
             return;
         case 0x3d1:
         case 0x3d5:
@@ -286,7 +301,8 @@ uint8_t
 ega_in(uint16_t addr, void *priv)
 {
     ega_t  *ega = (ega_t *) priv;
-    uint8_t ret = 0xff;
+    uint8_t gdcmask = (ega->actual_type == EGA_SUPEREGA) ? 0xff : 0x0f;
+    uint8_t ret     = 0xff;
 
     if (((addr & 0xfff0) == 0x3d0 || (addr & 0xfff0) == 0x3b0) && !(ega->miscout & 1))
         addr ^= 0x60;
@@ -347,8 +363,25 @@ ega_in(uint16_t addr, void *priv)
                 ret = ega->gdcaddr;
             break;
         case 0x3cf:
-            if (ega_type == EGA_TYPE_OTHER)
-                ret = ega->gdcreg[ega->gdcaddr & 0xf];
+            if (ega_type == EGA_TYPE_OTHER) {
+                switch (ega->gdcaddr & gdcmask) {
+                    default:
+                        ret = ega->gdcreg[ega->gdcaddr & gdcmask];
+                        break;
+                    case 0xf8:
+                        ret = ega->la;
+                        break;
+                    case 0xf9:
+                        ret = ega->lb;
+                        break;
+                    case 0xfa:
+                        ret = ega->lc;
+                        break;
+                    case 0xfb:
+                        ret = ega->ld;
+                        break;
+                }
+            }
             break;
         case 0x3d0:
         case 0x3d4:
@@ -1428,6 +1461,30 @@ ega_init(ega_t *ega, int monitor_type, int is_mono)
         timer_add(&ega->dot_timer, ega_dot_poll, ega, 1);
 }
 
+void
+ega_set_type(void *priv, uint32_t local)
+{
+    ega_t *ega = (ega_t *) priv;
+
+    if ((local == EGA_IBM) || (local == EGA_ISKRA) || (local == EGA_TSENG))
+        ega_type = EGA_TYPE_IBM;
+    else if (local == EGA_COMPAQ)
+        ega_type = EGA_TYPE_COMPAQ;
+    else
+        ega_type = EGA_TYPE_OTHER;
+
+    ega->actual_type = local;
+    ega->chipset = 0;
+
+    switch (local) {
+        default:
+            break;
+        case EGA_ATI800P:
+            ega->chipset = 1;
+            break;
+    }
+}
+
 static void *
 ega_standalone_init(const device_t *info)
 {
diff --git a/src/video/vid_jega.c b/src/video/vid_jega.c
index c410a15da..145579cf5 100644
--- a/src/video/vid_jega.c
+++ b/src/video/vid_jega.c
@@ -632,7 +632,7 @@ jega_init(const device_t *info)
     video_inform(VIDEO_FLAG_TYPE_SPECIAL, &timing_ega);
     jega->pallook = pallook64;
     ega_init(&jega->ega, 9, 0);
-    jega->ega.actual_type = EGA_SUPEREGA;
+    ega_set_type(&jega->ega, EGA_SUPEREGA);
     jega->ega.priv_parent = jega;
     mem_mapping_add(&jega->ega.mapping, 0xa0000, 0x20000, ega_read, NULL, NULL, ega_write, NULL, NULL, NULL, MEM_MAPPING_EXTERNAL, &jega->ega);