From 2ffff44957ae0393f895f5ad30d4888b2682e791 Mon Sep 17 00:00:00 2001
From: Toni Wilen <twilen@winuae.net>
Date: Sun, 6 Nov 2022 18:50:30 +0200
Subject: [PATCH] AGA EHB instant on/off

---
 custom.cpp  | 24 ++++++++++++++++++------
 drawing.cpp |  7 ++++++-
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/custom.cpp b/custom.cpp
index 05e47b76..69e5f429 100644
--- a/custom.cpp
+++ b/custom.cpp
@@ -948,10 +948,14 @@ static void record_color_change2(int hpos, int regno, uae_u32 value)
 	int pos = hpos < 0 ? -hpos : hpos_to_diwx(hpos);
 
 	// AGA has extra hires pixel delay in color changes
-	if ((regno < RECORDED_REGISTER_CHANGE_OFFSET || regno == RECORDED_REGISTER_CHANGE_OFFSET + 0x10c) && aga_mode) {
+	if ((regno < RECORDED_REGISTER_CHANGE_OFFSET || regno == RECORDED_REGISTER_CHANGE_OFFSET + 0x10c || regno == RECORDED_REGISTER_CHANGE_OFFSET + 0x201) && aga_mode) {
 		if (currprefs.chipset_hr) {
 			pos += 2;
 		}
+		if (regno == RECORDED_REGISTER_CHANGE_OFFSET + 0x201) {
+			// EHB delay
+			pos += 2;
+		}
 		if (regno == RECORDED_REGISTER_CHANGE_OFFSET + 0x10c) {
 			// BPLCON4:
 			// Bitplane XOR change: 2 hires pixel delay
@@ -4645,11 +4649,11 @@ static void record_register_change(int hpos, int regno, uae_u16 value)
 	if (regno == 0x0100 || regno == 0x0101) { // BPLCON0
 		if (value & 0x800)
 			thisline_decision.ham_seen = 1;
-		thisline_decision.ehb_seen = isehb(value, bplcon2);
+		thisline_decision.ehb_seen |= isehb(value, bplcon2);
 		isbrdblank(hpos, value, bplcon3);
 		issprbrd(hpos, value, bplcon3);
 	} else if (regno == 0x104) { // BPLCON2
-		thisline_decision.ehb_seen = isehb(bplcon0, value);
+		thisline_decision.ehb_seen |= isehb(bplcon0, value);
 	} else if (regno == 0x106) { // BPLCON3
 		isbrdblank(hpos, bplcon0, value);
 		issprbrd(hpos, bplcon0, value);
@@ -5616,9 +5620,9 @@ static void reset_decisions_hsync_start(void)
 	thisline_decision.plfleft = -1;
 	thisline_decision.plflinelen = -1;
 	thisline_decision.plfright = -1;
-	thisline_decision.ham_seen = !!(bplcon0 & 0x800);
-	thisline_decision.ehb_seen = !!isehb(bplcon0, bplcon2);
-	thisline_decision.ham_at_start = !!(bplcon0 & 0x800);
+	thisline_decision.ham_seen = (bplcon0 & 0x800) != 0;
+	thisline_decision.ehb_seen = isehb(bplcon0, bplcon2);
+	thisline_decision.ham_at_start = (bplcon0 & 0x800) != 0;
 	thisline_decision.bordersprite_seen = issprbrd(-1, bplcon0, bplcon3);
 	thisline_decision.xor_seen = (bplcon4 & 0xff00) != 0;
 	thisline_decision.nr_planes = toscr_nr_planes_agnus;
@@ -8059,6 +8063,14 @@ static void bplcon0_denise_change_early(int hpos, uae_u16 con0)
 	decide_line(hpos);
 	decide_fetch_safe(hpos);
 
+	if (aga_mode) {
+		int e1 = isehb(dcon0, bplcon2);
+		int e2 = isehb(dcon0o, bplcon2);
+		if (e1 ^ e2) {
+			record_register_change(hpos, 0x201, dcon0);
+		}
+	}
+
 	toscr_nr_planes_shifter_new = np;
 	if (ecs_denise || aga_mode) {
 		toscr_nr_changed = np != toscr_nr_planes3 && res == toscr_res;
diff --git a/drawing.cpp b/drawing.cpp
index 3e23a02f..702fc3c5 100644
--- a/drawing.cpp
+++ b/drawing.cpp
@@ -256,6 +256,7 @@ static int vblank_top_start, vblank_bottom_stop;
 static int hblank_left_start, hblank_right_stop;
 static int hblank_left_start_hard, hblank_right_stop_hard;
 static bool exthblank, extborder, exthblanken, exthblankon;
+static bool ehb_enable;
 
 static int linetoscr_x_adjust_pixbytes, linetoscr_x_adjust_pixels;
 static int thisframe_y_adjust;
@@ -3257,7 +3258,7 @@ static void pfield_expand_dp_bplcon(void)
 	bplres = dp_for_drawing->bplres;
 	bplplanecnt = dp_for_drawing->nr_planes;
 	bplham = dp_for_drawing->ham_seen;
-	bplehb = dp_for_drawing->ehb_seen;
+	bplehb = dp_for_drawing->ehb_seen && ehb_enable;
 	if (ecs_denise) {
 		// Check for KillEHB bit in ECS/AGA
 		if (dp_for_drawing->bplcon2 & 0x0200) {
@@ -3379,6 +3380,9 @@ static void pfield_expand_dp_bplconx (int regno, int v, int hp, int vp)
 		dp_for_drawing->ham_seen = isham(v);
 		extblankcheck();
 		break;
+	case 0x201: // AGA EHB immediate change
+		ehb_enable = (v & 0x7010) == 0x6000;
+		break;
 	case 0x104: // BPLCON2
 		dp_for_drawing->bplcon2 = v;
 		break;
@@ -5160,6 +5164,7 @@ void reset_drawing(void)
 	exthblankon = false;
 	extborder = false;
 	display_reset = 1;
+	ehb_enable = true;
 
 	lores_reset ();
 
-- 
2.47.3