From e57d93400e39c70fbfcc37985fde1909d0520e0a Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Sat, 29 Jul 2023 04:27:35 +0000
Subject: [PATCH] main: start vdp1 drawing immediately after updating the
 command list

This appears to reduce position artifacts between vdp1/vdp2 drawings.
---
 main.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/main.cpp b/main.cpp
index b644d52..c1150cd 100644
--- a/main.cpp
+++ b/main.cpp
@@ -463,8 +463,12 @@ void render()
 
   render_sprites(offset);
 
+  vdp1.reg.PTMR = PTMR__PTM__NOW;
+
   vdp2.reg.SCXIN0 = offset.x;
+  vdp2.reg.SCXDN0 = 0;
   vdp2.reg.SCYIN0 = offset.y;
+  vdp2.reg.SCYDN0 = 0;
 
   render_map();
 }
@@ -480,8 +484,8 @@ void v_blank_in_int()
   sh2.reg.FRC.L = 0;
   sh2.reg.FTCSR = 0; // clear flags
 
-  update();
   render();
+  update();
 
   // wait at least 300us, as specified in the SMPC manual.
   // It appears reading FRC.H is mandatory and *must* occur before FRC.L on real
@@ -549,7 +553,7 @@ void init_vdp1()
   vdp1.vram.cmd[2].CTRL = CTRL__END;
 
   // start drawing (execute the command list) on every frame
-  vdp1.reg.PTMR = PTMR__PTM__FRAME_CHANGE;
+  //vdp1.reg.PTMR = PTMR__PTM__FRAME_CHANGE;
 }
 
 void init_vdp2()