VideoCommon: Add fallback handling for bounding box when disabled or unsupported

The SDK seems to write "default" bounding box values before every draw
(1023 0 1023 0 are the only values encountered so far, which happen to
be the extents allowed by the BP registers) to reset the registers for
comparison in the pixel engine, and presumably to detect whether GX has
updated the registers with real values. Handling these writes and
returning them on read when bounding box emulation is disabled or
unsupported, even without computing real values from rendering, seems
to prevent games from corrupting memory or crashing.

This obviously does not fix any effects that rely on bounding box
emulation, but having the game not clobber its own code/data or just
outright crash is a definite improvement.

1 files changed, 10 insertions, 0 deletions

diff --git a/Source/Core/VideoCommon/RenderBase.cpp b/Source/Core/VideoCommon/RenderBase.cpp
index f93d498fc6..5422d26e94 100644
--- a/Source/Core/VideoCommon/RenderBase.cpp
+++ b/Source/Core/VideoCommon/RenderBase.cpp
@@ -187,11 +187,20 @@ void Renderer::ReinterpretPixelData(EFBReinterpretType convtype)
 
 u16 Renderer::BBoxRead(int index)
 {
+  if (!g_ActiveConfig.bBBoxEnable || !g_ActiveConfig.backend_info.bSupportsBBox)
+    return m_bounding_box_fallback[index];
+
   return BBoxReadImpl(index);
 }
 
 void Renderer::BBoxWrite(int index, u16 value)
 {
+  if (!g_ActiveConfig.bBBoxEnable || !g_ActiveConfig.backend_info.bSupportsBBox)
+  {
+    m_bounding_box_fallback[index] = value;
+    return;
+  }
+
   BBoxWriteImpl(index, value);
 }
 
@@ -1748,6 +1757,7 @@ void Renderer::DoState(PointerWrap& p)
   p.Do(m_last_xfb_width);
   p.Do(m_last_xfb_stride);
   p.Do(m_last_xfb_height);
+  p.DoArray(m_bounding_box_fallback);
 
   if (p.GetMode() == PointerWrap::MODE_READ)
   {