From 37c4aa74c9fe77c0cd9a52eda00713940b478834 Mon Sep 17 00:00:00 2001
From: Toni Wilen <twilen@winuae.net>
Date: Thu, 16 Jan 2025 20:57:56 +0200
Subject: [PATCH] Reimplement interlace scandoubler

---
 custom.cpp  | 14 ++++++++------
 drawing.cpp |  8 ++++++--
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/custom.cpp b/custom.cpp
index 8b99e24a..88dba25d 100644
--- a/custom.cpp
+++ b/custom.cpp
@@ -119,8 +119,8 @@ static uae_u32 custom_state_flags;
 static int not_safe_mode;
 static bool dmal_next;
 
-#define MAX_SCANDOUBLED_LINES 1000
-static uae_u32 scandoubled_bpl_ptr[MAX_SCANDOUBLED_LINES][8][2];
+#define MAX_SCANDOUBLED_LINES 1200
+static uae_u32 scandoubled_bpl_ptr[MAX_SCANDOUBLED_LINES][2][MAX_PLANES];
 
 static evt_t blitter_dma_change_cycle, copper_dma_change_cycle, sprite_dma_change_cycle_on, sprite_dma_change_cycle_off;
 
@@ -9637,7 +9637,7 @@ static void decide_bpl(int hpos)
 			ddf_enable_on = 1;
 			if (currprefs.gfx_scandoubler && vpos < MAX_SCANDOUBLED_LINES) {
 				for (int i = 0; i < MAX_PLANES; i++) {
-					scandoubled_bpl_ptr[vpos][i][lof_store] = bplpt[i];
+					scandoubled_bpl_ptr[vpos][lof_store][i] = bplpt[i];
 				}
 			}
 		}
@@ -9795,7 +9795,7 @@ static void decide_bpl(int hpos)
 			ddfstrt_match = true;
 			if (currprefs.gfx_scandoubler && vpos < MAX_SCANDOUBLED_LINES) {
 				for (int i = 0; i < MAX_PLANES; i++) {
-					scandoubled_bpl_ptr[vpos][i][lof_store] = bplpt[i];
+					scandoubled_bpl_ptr[vpos][lof_store][i] = bplpt[i];
 				}
 			}
 		} else {
@@ -10237,8 +10237,8 @@ static void do_scandouble(void)
 		if (rd->rga >= 0x110 && rd->rga < 0x120) {
 			int plane = (rd->rga - 0x110) / 2;
 			if (vp < MAX_SCANDOUBLED_LINES) {
-				uaecptr l1 = scandoubled_bpl_ptr[vp][plane][l];
-				uaecptr l2 = scandoubled_bpl_ptr[vp][plane][l ^ 1];
+				uaecptr l1 = scandoubled_bpl_ptr[vp][l][plane];
+				uaecptr l2 = scandoubled_bpl_ptr[vp][l ^ 1][plane];
 				rga.pv = rd->pt - l1 + l2;
 				if (fetchmode_fmode_bpl == 3) {
 					rd->v64 = fetch64(&rga);
@@ -10485,7 +10485,9 @@ static void decide_hsync(void)
 						do_scandouble();
 						denise_restore_registers();
 						lof_display ^= 1;
+						scandoubled_line = 1;
 						draw_line(linear_hpos);
+						scandoubled_line = 0;
 						lof_display ^= 1;
 					} else {
 						draw_line(linear_hpos);
diff --git a/drawing.cpp b/drawing.cpp
index 6c0fc6ce..1d530009 100644
--- a/drawing.cpp
+++ b/drawing.cpp
@@ -42,6 +42,8 @@
 #define AUTOSCALE_SPRITES 1
 #define LOL_SHIFT_COLORS 0
 
+int scandoubled_line;
+
 struct amigadisplay adisplays[MAX_AMIGADISPLAYS];
 
 typedef enum
@@ -4579,8 +4581,10 @@ static void matchsprites_aga(int cnt)
 }
 
 static uae_u16 s_bplcon0, s_bplcon1, s_bplcon2, s_bplcon3, s_bplcon4, s_fmode;
+static int denise_hcounter_s;
 void denise_store_registers(void)
 {
+	denise_hcounter_s = denise_hcounter; 
 	s_bplcon0 = bplcon0_denise;
 	s_bplcon1 = bplcon1_denise;
 	s_bplcon2 = bplcon2_denise;
@@ -4590,6 +4594,7 @@ void denise_store_registers(void)
 }
 void denise_restore_registers(void)
 {
+	denise_hcounter = denise_hcounter_s;
 	expand_bplcon0(s_bplcon0);
 	expand_bplcon1(s_bplcon1);
 	expand_bplcon2(s_bplcon2);
@@ -4798,7 +4803,7 @@ static void get_line(int gfx_ypos, enum nln_how how)
 	}
 
 	// clear lines if mode height is now smaller than previously
-	if (gfx_ypos >= 0 && gfx_ypos < prevline) {
+	if (gfx_ypos >= 0 && gfx_ypos < prevline && !scandoubled_line) {
 		struct vidbuf_description *vidinfo = &adisplays[0].gfxvidinfo;
 		struct vidbuffer *vb = &vidinfo->drawbuffer;
 		if (prevline > vb->inheight) {
@@ -4927,7 +4932,6 @@ void draw_denise_line(int gfx_ypos, enum nln_how how, uae_u32 linecnt, int start
 	get_line(gfx_ypos, how);
 	hbstrt_ptr1 = NULL;
 
-
 	if (denise_pixtotal_max == -0x7fffffff || ((linear_vpos >= denise_vblank_extra_vbstop || linear_vpos < denise_vblank_extra_vbstrt) && currprefs.gfx_overscanmode < OVERSCANMODE_ULTRA)) {
 
 		// don't draw vertical blanking if not ultra extreme overscan
-- 
2.47.3