make a workaround for streamout with no fbo

src/Cafe/HW/Latte/Renderer/Metal/CachedFBOMtl.cpp

@@ -7,6 +7,7 @@ CachedFBOMtl::CachedFBOMtl(class MetalRenderer* metalRenderer, uint64 key) : Lat
 {
 	m_renderPassDescriptor = MTL::RenderPassDescriptor::alloc()->init();
 
+	bool hasAttachment = false;
 	for (int i = 0; i < 8; ++i)
 	{
 		const auto& buffer = colorBuffer[i];
@@ -19,6 +20,8 @@ CachedFBOMtl::CachedFBOMtl(class MetalRenderer* metalRenderer, uint64 key) : Lat
 		colorAttachment->setTexture(textureView->GetRGBAView());
 		colorAttachment->setLoadAction(MTL::LoadActionLoad);
 		colorAttachment->setStoreAction(MTL::StoreActionStore);
+
+		hasAttachment = true;
 	}
 
 	// setup depth attachment
@@ -38,6 +41,17 @@ CachedFBOMtl::CachedFBOMtl(class MetalRenderer* metalRenderer, uint64 key) : Lat
             stencilAttachment->setLoadAction(MTL::LoadActionLoad);
             stencilAttachment->setStoreAction(MTL::StoreActionStore);
 		}
+
+		hasAttachment = true;
+	}
+
+	// HACK: setup a dummy color attachment to prevent Metal from discarding draws for stremout draws in Super Smash Bros. for Wii U (works fine on MoltenVK without this hack though)
+	if (!hasAttachment)
+	{
+        auto colorAttachment = m_renderPassDescriptor->colorAttachments()->object(0);
+    	colorAttachment->setTexture(metalRenderer->GetNullTexture2D());
+    	colorAttachment->setLoadAction(MTL::LoadActionDontCare);
+    	colorAttachment->setStoreAction(MTL::StoreActionDontCare);
 	}
 
 	// Visibility buffer

src/Cafe/HW/Latte/Renderer/Metal/MetalPipelineCache.cpp

@@ -10,6 +10,7 @@
 #include "Cafe/HW/Latte/Core/FetchShader.h"
 #include "Cafe/HW/Latte/ISA/RegDefines.h"
 #include "Cemu/Logging/CemuLogging.h"
+#include "HW/Latte/Core/LatteConst.h"
 #include "config/ActiveSettings.h"
 
 static void rectsEmulationGS_outputSingleVertex(std::string& gsSrc, const LatteDecompilerShader* vertexShader, LatteShaderPSInputTable* psInputTable, sint32 vIdx, const LatteContextRegister& latteRegister)
@@ -206,20 +207,21 @@ void SetFragmentState(T* desc, CachedFBOMtl* lastUsedFBO, CachedFBOMtl* activeFB
 	if (cullFront && cullBack)
 	    rasterizationEnabled = false;
 
-	if (!rasterizationEnabled)
+	auto pixelShaderMtl = static_cast<RendererShaderMtl*>(pixelShader->shader);
+
+	if (!rasterizationEnabled || !pixelShaderMtl)
 	{
 	    desc->setRasterizationEnabled(false);
 		return;
 	}
 
-    auto pixelShaderMtl = static_cast<RendererShaderMtl*>(pixelShader->shader);
+    desc->setFragmentFunction(pixelShaderMtl->GetFunction());
-	desc->setFragmentFunction(pixelShaderMtl->GetFunction());
 
     // Color attachments
 	const Latte::LATTE_CB_COLOR_CONTROL& colorControlReg = lcr.CB_COLOR_CONTROL;
 	uint32 blendEnableMask = colorControlReg.get_BLEND_MASK();
 	uint32 renderTargetMask = lcr.CB_TARGET_MASK.get_MASK();
-	for (uint8 i = 0; i < 8; i++)
+	for (uint8 i = 0; i < LATTE_NUM_COLOR_TARGET; i++)
 	{
 	    const auto& colorBuffer = lastUsedFBO->colorBuffer[i];
 		auto texture = static_cast<LatteTextureViewMtl*>(colorBuffer.texture);

src/Cafe/HW/Latte/Renderer/Metal/MetalRenderer.cpp

@@ -863,7 +863,6 @@ void MetalRenderer::draw_beginSequence()
 			return; // no render target
 		}
 
-		// TODO: not checking for !streamoutEnable fixes Super Smash Bros. for Wii U, investigate why
 		if (!hasValidFramebufferAttached && !streamoutEnable)
 		{
 			debug_printf("Drawcall with no color buffer or depth buffer attached\n");
@@ -1476,10 +1475,6 @@ MTL::RenderCommandEncoder* MetalRenderer::GetRenderCommandEncoder(bool forceRecr
 
     auto commandBuffer = GetCommandBuffer();
 
-    // Update state
-    m_state.m_lastUsedFBO = m_state.m_activeFBO;
-    m_state.m_isFirstDrawInRenderPass = true;
-
     auto renderCommandEncoder = commandBuffer->renderCommandEncoder(m_state.m_activeFBO->GetRenderPassDescriptor());
 #ifdef CEMU_DEBUG_ASSERT
     renderCommandEncoder->setLabel(GetLabel("Render command encoder", renderCommandEncoder));
@@ -1487,6 +1482,10 @@ MTL::RenderCommandEncoder* MetalRenderer::GetRenderCommandEncoder(bool forceRecr
     m_commandEncoder = renderCommandEncoder;
     m_encoderType = MetalEncoderType::Render;
 
+    // Update state
+    m_state.m_lastUsedFBO = m_state.m_activeFBO;
+    m_state.m_isFirstDrawInRenderPass = true;
+
     ResetEncoderState();
 
     // Debug

src/Cafe/HW/Latte/Renderer/Metal/MetalRenderer.h

@@ -380,6 +380,11 @@ public:
         return (m_hasUnifiedMemory ? MTL::ResourceStorageModeShared : MTL::ResourceStorageModeManaged);
     }
 
+    MTL::Texture* GetNullTexture2D() const
+    {
+        return m_nullTexture2D;
+    }
+
     MTL::Buffer* GetTextureReadbackBuffer()
     {
         if (!m_readbackBuffer)