VideoCommon: Abstract bounding box

This moves much of the duplicated bounding box code into VideoCommon,
leaving only the specific buffer implementations in each backend.

Source/Core/VideoBackends/Null/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_library(videonull
   NullBackend.cpp
+  NullBoundingBox.h
   NullRender.cpp
   NullRender.h
   NullTexture.cpp

Source/Core/VideoBackends/Null/NullBoundingBox.h

@@ -0,0 +1,25 @@
+// Copyright 2021 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "Common/CommonTypes.h"
+
+#include "VideoCommon/BoundingBox.h"
+
+namespace Null
+{
+class NullBoundingBox final : public BoundingBox
+{
+public:
+  bool Initialize() override { return true; }
+
+protected:
+  std::vector<BBoxType> Read(u32 index, u32 length) override
+  {
+    return std::vector<BBoxType>(length);
+  }
+  void Write(u32 index, const std::vector<BBoxType>& values) override {}
+};
+
+}  // namespace Null

Source/Core/VideoBackends/Null/NullRender.cpp

@@ -3,6 +3,7 @@
 
 #include "VideoBackends/Null/NullRender.h"
 
+#include "VideoBackends/Null/NullBoundingBox.h"
 #include "VideoBackends/Null/NullTexture.h"
 
 #include "VideoCommon/AbstractPipeline.h"
@@ -83,4 +84,9 @@ Renderer::CreateNativeVertexFormat(const PortableVertexDeclaration& vtx_decl)
 {
   return std::make_unique<NativeVertexFormat>(vtx_decl);
 }
+
+std::unique_ptr<BoundingBox> Renderer::CreateBoundingBox() const
+{
+  return std::make_unique<NullBoundingBox>();
+}
 }  // namespace Null

Source/Core/VideoBackends/Null/NullRender.h

@@ -5,6 +5,8 @@
 
 #include "VideoCommon/RenderBase.h"
 
+class BoundingBox;
+
 namespace Null
 {
 class Renderer final : public ::Renderer
@@ -35,8 +37,6 @@ public:
 
   u32 AccessEFB(EFBAccessType type, u32 x, u32 y, u32 poke_data) override { return 0; }
   void PokeEFB(EFBAccessType type, const EfbPokeData* points, size_t num_points) override {}
-  u16 BBoxReadImpl(int index) override { return 0; }
-  void BBoxWriteImpl(int index, u16 value) override {}
 
   void ClearScreen(const MathUtil::Rectangle<int>& rc, bool colorEnable, bool alphaEnable,
                    bool zEnable, u32 color, u32 z) override
@@ -44,5 +44,8 @@ public:
   }
 
   void ReinterpretPixelData(EFBReinterpretType convtype) override {}
+
+protected:
+  std::unique_ptr<BoundingBox> CreateBoundingBox() const override;
 };
 }  // namespace Null