From 664bd06df6539de8f3d386e5c568a7e6f15a27ef Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Sun, 17 May 2020 17:58:47 +1000
Subject: [PATCH] GPU: Don't recursively execute commands

This can happen with interlaced rendering on when a line is pending
scanout and a primitive is drawn.

Fixes screen transitions in Slap Happy Rhythm Busters.
---
 src/core/gpu.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/core/gpu.cpp b/src/core/gpu.cpp
index b2277ae1f..a00a236e8 100644
--- a/src/core/gpu.cpp
+++ b/src/core/gpu.cpp
@@ -619,7 +619,11 @@ void GPU::Execute(TickCount ticks)
     if (m_command_ticks > 0)
     {
       m_command_ticks -= gpu_ticks;
-      ExecuteCommands();
+
+      // we can be syncing if this came from a DMA write. recursively executing commands would be bad.
+      if (!m_syncing)
+        ExecuteCommands();
+
       if (m_command_ticks < 0)
         m_command_ticks = 0;
     }