From 8fe70b0a6e2def8ac650beb55e5213ea23c6c0ef Mon Sep 17 00:00:00 2001
From: Ben Russell <thematrixeatsyou@gmail.com>
Date: Fri, 24 Mar 2023 21:50:06 +0000
Subject: [PATCH] vid_ega: Make the read-write CRTC registers readable

This fixes a lockup that happens when returning from QBASIC under many screen modes, including SCREEN 0.
---
 src/video/vid_ega.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index b85863e8d..3da38da35 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -312,8 +312,25 @@ ega_in(uint16_t addr, void *p)
             break;
         case 0x3d1:
         case 0x3d5:
-            if (ega_type)
-                ret = ega->crtc[ega->crtcreg];
+            switch(ega->crtcreg) {
+                case 0xc:
+                case 0xd:
+                case 0xe:
+                case 0xf:
+                    ret = ega->crtc[ega->crtcreg];
+                    break;
+
+                case 0x10:
+                case 0x11:
+                    // TODO: Return light pen address once implemented
+                    if (ega_type)
+                        ret = ega->crtc[ega->crtcreg];
+                    break;
+
+                default:
+                    if (ega_type)
+                        ret = ega->crtc[ega->crtcreg];
+            }
             break;
         case 0x3da:
             ega->attrff = 0;