From 646e25f1bc524f21fc6a74045986142652c1cb21 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Sun, 23 Mar 2025 02:22:10 +0100
Subject: [PATCH] EGA: Implement monochrome attributes for text mode.

---
 src/video/vid_ega.c        | 20 ++++++++++++++++++++
 src/video/vid_ega_render.c | 12 ++++++++++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index c7345cd00..438d5c98d 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -1447,6 +1447,26 @@ ega_init(ega_t *ega, int monitor_type, int is_mono)
 
     ega->pallook = pallook16;
 
+    for (uint16_t c = 0; c < 256; c++) {
+        ega->mdacols[c][0][0] = ega->mdacols[c][1][0] = ega->mdacols[c][1][1] = 16;
+        if (c & 8)
+            ega->mdacols[c][0][1] = 15 + 16;
+        else
+            ega->mdacols[c][0][1] = 7 + 16;
+    }
+    ega->mdacols[0x70][0][1] = 16;
+    ega->mdacols[0x70][0][0] = ega->mdacols[0x70][1][0] = ega->mdacols[0x70][1][1] = 16 + 15;
+    ega->mdacols[0xF0][0][1]                                                       = 16;
+    ega->mdacols[0xF0][0][0] = ega->mdacols[0xF0][1][0] = ega->mdacols[0xF0][1][1] = 16 + 15;
+    ega->mdacols[0x78][0][1]                                                       = 16 + 7;
+    ega->mdacols[0x78][0][0] = ega->mdacols[0x78][1][0] = ega->mdacols[0x78][1][1] = 16 + 15;
+    ega->mdacols[0xF8][0][1]                                                       = 16 + 7;
+    ega->mdacols[0xF8][0][0] = ega->mdacols[0xF8][1][0] = ega->mdacols[0xF8][1][1] = 16 + 15;
+    ega->mdacols[0x00][0][1] = ega->mdacols[0x00][1][1] = 16;
+    ega->mdacols[0x08][0][1] = ega->mdacols[0x08][1][1] = 16;
+    ega->mdacols[0x80][0][1] = ega->mdacols[0x80][1][1] = 16;
+    ega->mdacols[0x88][0][1] = ega->mdacols[0x88][1][1] = 16;
+
     egaswitches = monitor_type & 0xf;
 
     ega->vram_limit = 256 * 1024;
diff --git a/src/video/vid_ega_render.c b/src/video/vid_ega_render.c
index fe2632574..d499154e6 100644
--- a/src/video/vid_ega_render.c
+++ b/src/video/vid_ega_render.c
@@ -118,6 +118,7 @@ ega_render_text(ega_t *ega)
         const bool doublewidth   = ((ega->seqregs[1] & 8) != 0);
         const bool attrblink     = ((ega->attrregs[0x10] & 8) != 0);
         const bool attrlinechars = (ega->attrregs[0x10] & 4);
+        const bool monoattrs     = (ega->attrregs[0x10] & 2);
         const bool crtcreset     = ((ega->crtc[0x17] & 0x80) == 0);
         const bool seq9dot       = ((ega->seqregs[1] & 1) == 0);
         const int  dwshift       = doublewidth ? 1 : 0;
@@ -174,8 +175,15 @@ ega_render_text(ega_t *ega)
             if ((chr & ~0x1F) == 0xC0 && attrlinechars)
                 dat |= (dat >> 1) & 1;
 
-            for (int xx = 0; xx < charwidth; xx++)
-                p[xx] = (dat & (0x100 >> (xx >> dwshift))) ? fg : bg;
+            for (int xx = 0; xx < charwidth; xx++) {
+                if (monoattrs) {
+                    if ((ega->sc == (ega->crtc[0x14] + 1)) && ((attr & 7) == 1))
+                        p[xx] = ega->mdacols[attr][attrblink][1];
+                    else
+                        p[xx] = ega->mdacols[attr][attrblink][dat & (0x100 >> (xx >> dwshift))];
+                } else
+                    p[xx] = (dat & (0x100 >> (xx >> dwshift))) ? fg : bg;
+            }
 
             ega->ma += 4;
             p += charwidth;