From a5f46ef64ecb8de789a34ea5dcde18a0700de88b Mon Sep 17 00:00:00 2001
From: Toni Wilen <twilen@winuae.net>
Date: Sat, 28 Mar 2026 16:14:06 +0200
Subject: [PATCH] Fix A2024 (others later)

---
 custom.cpp          | 14 +++++++++++---
 drawing.cpp         |  4 +++-
 include/drawing.h   |  1 +
 specialmonitors.cpp | 19 ++++++++++++++-----
 4 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/custom.cpp b/custom.cpp
index 13ff0054..d620cea9 100644
--- a/custom.cpp
+++ b/custom.cpp
@@ -393,6 +393,7 @@ static int next_lineno;
 int linear_vpos, linear_vpos_vb_start, linear_vpos_vb_end, linear_hpos, linear_vpos_prev[3], linear_hpos_prev[3];
 static int linear_vb_offset;
 static int linear_vpos_vsync;
+int vsync_start_offset;
 int linear_display_vpos;
 int current_linear_vpos, current_linear_hpos;
 static int current_linear_hblen, current_linear_hblen_temp;
@@ -1686,7 +1687,9 @@ void compute_framesync(void)
 	if (currprefs.cs_hvcsync >= HVSYNC_SYNCPOS) {
 		vblines = LINES_AFTER_VSYNC;
 	}
-	int maxv = current_linear_vpos - (vblines - display_vblankstart_skip) + display_vblankend_skip + 1;
+	int hiddentopv = (vblines - display_vblankstart_skip);
+	int hiddenbottomv = display_vblankend_skip;
+	int maxv = current_linear_vpos - (hiddentopv + hiddenbottomv) + 1;
 	linear_vpos_vb_end = current_linear_vpos_vb_end - display_vblankstart_skip - 1;
 	if (currprefs.gfx_overscanmode >= OVERSCANMODE_ULTRA) {
 		maxv = current_linear_vpos;
@@ -4612,7 +4615,8 @@ static void cursorsprite(struct sprite *s)
 
 static int calculate_linetype(int vp)
 {
-	int lineno = vp - (currprefs.cs_hvcsync >= HVSYNC_SYNCPOS ? LINES_AFTER_VSYNC : linear_vb_offset);
+	int off = currprefs.cs_hvcsync >= HVSYNC_SYNCPOS ? LINES_AFTER_VSYNC : linear_vb_offset;
+	int lineno = vp - off;
 	nextline_how = nln_normal;
 	if (doflickerfix_active()) {
 		lineno *= 2;
@@ -10086,7 +10090,7 @@ static void vsync_mark(void)
 		if (!vb_end_detect) {
 			vb_detect_cnt++;
 			if (vb_detect_cnt >= 4) {
-				// if VB does not exists
+				// if VB does not exist
 				linear_vpos_vblank_end = LINES_AFTER_VSYNC;
 				linear_vpos_vblank_start = linear_vpos;
 				linear_vpos_vblank_lines = LINES_AFTER_VSYNC;
@@ -10099,6 +10103,10 @@ static void vsync_mark(void)
 		}
 		vb_end_detect = false;
 		linear_vpos = 0;
+
+		int off = currprefs.cs_hvcsync >= HVSYNC_SYNCPOS ? LINES_AFTER_VSYNC : linear_vb_offset;
+		vsync_start_offset = -off;
+
 	}
 }
 
diff --git a/drawing.cpp b/drawing.cpp
index 9292ad2e..34512c7a 100644
--- a/drawing.cpp
+++ b/drawing.cpp
@@ -1529,7 +1529,7 @@ static void center_image(void)
 	}
 
 	vidinfo->inbuffer->xoffset = visible_left_border << (RES_MAX - currprefs.gfx_resolution);
-	vidinfo->inbuffer->yoffset = thisframe_y_adjust << VRES_MAX;
+	vidinfo->inbuffer->yoffset = (-vsync_start_offset) << VRES_MAX;
 
 	int linedbl = currprefs.gfx_vresolution;
 	if (doublescan > 0 && interlace_seen <= 0) {
@@ -2029,6 +2029,8 @@ static void setspecialmonitorpos(struct vidbuffer *vb)
 	vb->yoffset = vidinfo->inbuffer->yoffset;
 	vb->inxoffset = vidinfo->inbuffer->inxoffset;
 	vb->inyoffset = vidinfo->inbuffer->inyoffset;
+	vb->outwidth = vidinfo->inbuffer->outwidth;
+	vb->outheight = vidinfo->inbuffer->outheight;
 }
 
 static void vbcopy(struct vidbuffer *vbout, struct vidbuffer *vbin)
diff --git a/include/drawing.h b/include/drawing.h
index 2bd86d68..4ba9dfb1 100644
--- a/include/drawing.h
+++ b/include/drawing.h
@@ -25,6 +25,7 @@ extern int detected_screen_resolution;
 extern int hdisplay_left_border, denisehtotal;
 extern int vsync_startline;
 extern int video_recording_active;
+extern int vsync_start_offset;
 
 #define AMIGA_WIDTH_MAX (754 / 2)
 #define AMIGA_HEIGHT_MAX_PAL (576 / 2)
diff --git a/specialmonitors.cpp b/specialmonitors.cpp
index b9b25f26..db082306 100755
--- a/specialmonitors.cpp
+++ b/specialmonitors.cpp
@@ -1,3 +1,11 @@
+/*
+* UAE - The Un*x Amiga Emulator
+*
+* Video port display adapters using digital RGBI signals
+*
+*/
+
+
 #include "sysconfig.h"
 #include "sysdeps.h"
 
@@ -18,9 +26,6 @@
 #include "arcadia.h"
 #include "uae/attributes.h"
 
-// We have this in sysconfig.h
-//#define VIDEOGRAB 1
-
 const TCHAR *specialmonitorfriendlynames[] =
 {
 	_T("A2024"),
@@ -2051,7 +2056,7 @@ static bool a2024(struct vidbuffer *src, struct vidbuffer *dst)
 	doff = ((dxoff << RES_MAX) / avidinfo->xchange) * src->pixbytes;
 	found = false;
 
-	int idlinestart = 21;
+	int idlinestart = 18;
 	for (idline = idlinestart; idline <= idlinestart + 8; idline += 8) {
 		if (src->yoffset > (idline << VRES_MAX))
 			continue;
@@ -2169,7 +2174,11 @@ static bool a2024(struct vidbuffer *src, struct vidbuffer *dst)
 		return false;
 	}
 
-	srcbuf = src->bufmem + (((44 << VRES_MAX) - src->yoffset) / avidinfo->ychange) * src->rowbytes + (srcxoffset / avidinfo->xchange) * src->pixbytes;
+	int ystart = 82 - src->yoffset;
+	if (ystart < 0) {
+		return false;
+	}
+	srcbuf = src->bufmem + (ystart / avidinfo->ychange) * src->rowbytes + (srcxoffset / avidinfo->xchange) * src->pixbytes;
 	dstbuf = dst->bufmem + py * (panel_height / avidinfo->ychange) * dst->rowbytes + px * ((panel_width * 2) / avidinfo->xchange) * dst->pixbytes;
 
 	for (y = 0; y < (panel_height / (dbl == 1 ? 1 : 2)) / avidinfo->ychange; y++) {
-- 
2.47.3