From 9844cbc2459cc33d18ae17253e431547e5504579 Mon Sep 17 00:00:00 2001
From: GreaseMonkey <thematrixeatsyou@gmail.com>
Date: Tue, 23 Jan 2024 16:02:32 +1300
Subject: [PATCH 1/3] Add 8-dot hscroll compensation to EGA graphics modes

This is in lieu of whatever the correct emulation would be (as per the text modes).
Somehow I forgot to add this when reworking the fine scroll implementations.
---
 src/video/vid_ega_render.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/video/vid_ega_render.c b/src/video/vid_ega_render.c
index 98905e0c8..0cb1216ad 100644
--- a/src/video/vid_ega_render.c
+++ b/src/video/vid_ega_render.c
@@ -199,6 +199,7 @@ ega_render_graphics(ega_t *ega)
     const bool    attrblink   = ((ega->attrregs[0x10] & 8) != 0);
     const bool    blinked     = ega->blink & 0x10;
     const bool    crtcreset   = ((ega->crtc[0x17] & 0x80) == 0);
+    const bool    seq9dot       = ((ega->seqregs[1] & 1) == 0);
     const bool    seqoddeven  = ((ega->seqregs[1] & 4) != 0);
     const uint8_t blinkmask   = (attrblink && blinked ? 0x8 : 0x0);
     uint32_t     *p           = &buffer32->line[ega->displine + ega->y_add][ega->x_add];
@@ -206,6 +207,15 @@ ega_render_graphics(ega_t *ega)
     const int     dotwidth    = 1 << dwshift;
     const int     charwidth   = dotwidth * 8;
     int           secondcclk  = 0;
+
+    /* Compensate for 8dot scroll */
+    if (!seq9dot) {
+        for (int x = 0; x < dotwidth; x++) {
+            p[x] = ega->overscan_color;
+        }
+        p += dotwidth;
+    }
+
     for (int x = 0; x <= (ega->hdisp + ega->scrollcache); x += charwidth) {
         uint32_t addr = ega->remap_func(ega, ega->ma) & ega->vrammask;
 

From e5000f7419d1020c4e657b4168f91658d3b1c746 Mon Sep 17 00:00:00 2001
From: GreaseMonkey <thematrixeatsyou@gmail.com>
Date: Tue, 23 Jan 2024 17:03:33 +1300
Subject: [PATCH 2/3] Fix fine scroll wobbling in EGA when calling
 `ega_recalctimings`

Closes: GH-4072
---
 src/video/vid_ega.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index 670d88e61..282fde656 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -557,7 +557,7 @@ ega_recalctimings(ega_t *ega)
         overscan_x <<= 1;
 
     ega->y_add = (overscan_y >> 1);
-    ega->x_add = (overscan_x >> 1);
+    ega->x_add = (overscan_x >> 1) - ega->scrollcache;
 
     if (ega->vres)
         ega->y_add >>= 1;

From 257cf0d1a2cb18bfd28cf5230a9a8bf27198a492 Mon Sep 17 00:00:00 2001
From: GreaseMonkey <thematrixeatsyou@gmail.com>
Date: Tue, 23 Jan 2024 17:06:39 +1300
Subject: [PATCH 3/3] Remove the "reset horizontal fine scroll on split screen"
 VGAism from EGA

---
 src/video/vid_ega.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index 282fde656..7979cd958 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -804,10 +804,6 @@ ega_poll(void *priv)
             ega->cca = ega->ma;
             ega->maback <<= 2;
             ega->sc = 0;
-            if (ega->attrregs[0x10] & 0x20) {
-                ega->scrollcache = 0;
-                ega->x_add       = (overscan_x >> 1);
-            }
         }
         if (ega->vc == ega->dispend) {
             ega->dispon = 0;