GPU: Completely revert commit a948838. I forgot that Zelda PH and Zelda ST could use both GPU engines for the same display when moving the map to and from the touch screen, and so native line tracking MUST be performed at the display level in order to account for this.

- Added some additional comments so that I'm not tempted to change the native line tracking paradigm ever again.
- Do some refactoring to make GPUEngineBase::_targetDisplay handle more buffer associations itself instead of relying on GPUEngineBase's copies of the associations.

desmume/src/GPU.h

@@ -63,6 +63,7 @@
 #endif
 
 class GPUEngineBase;
+class NDSDisplay;
 class EMUFILE;
 class Task;
 struct MMU_struct;
@@ -1175,7 +1176,6 @@ typedef struct
 												// GPUSubsystem::ResolveDisplayToCustomFramebuffer() is called, then this buffer is used as the
 												// target buffer for resolving any native-sized renders.
 	
-	u32 *workingNativeBuffer32[2];				// Pointer to a native size working framebuffer. (Usually used as an intermediate buffer for internal use, but might be useful for the client.)
 	u16 *nativeBuffer16[2];						// Pointer to the display's native size framebuffer.
 	void *customBuffer[2];						// Pointer to the display's custom size framebuffer.
 	
@@ -1389,13 +1389,7 @@ protected:
 	u8 *_deferredIndexCustom;
 	u16 *_deferredColorCustom;
 	
-	u16 *_nativeBuffer16;
-	u32 *_workingNativeBuffer32;
-	void *_customBuffer;
-	
 	bool _isLineRenderNative[GPU_FRAMEBUFFER_NATIVE_HEIGHT];
-	bool _isLineDisplayNative[GPU_FRAMEBUFFER_NATIVE_HEIGHT];
-	size_t _nativeLineDisplayCount;
 	
 	bool _enableEngine;
 	bool _enableBGLayer[5];
@@ -1426,7 +1420,7 @@ protected:
 	CACHE_ALIGN u8 _sprNum[256];
 	CACHE_ALIGN u8 _h_win[2][GPU_FRAMEBUFFER_NATIVE_WIDTH];
 	
-	NDSDisplayID _targetDisplayID;
+	NDSDisplay *_targetDisplay;
 	
 	CACHE_ALIGN u16 _internalRenderLineTargetNative[GPU_FRAMEBUFFER_NATIVE_WIDTH];
 	CACHE_ALIGN u8 _renderLineLayerIDNative[GPU_FRAMEBUFFER_NATIVE_HEIGHT][GPU_FRAMEBUFFER_NATIVE_WIDTH];
@@ -1519,6 +1513,7 @@ public:
 	
 	void SetupBuffers();
 	void SetupRenderStates();
+	void DisplayDrawBuffersUpdate();
 	template<NDSColorFormat OUTPUTFORMAT> void UpdateRenderStates(const size_t l);
 	template<NDSColorFormat OUTPUTFORMAT> void RenderLine(const size_t l);
 	
@@ -1583,14 +1578,12 @@ public:
 	void RenderLayerBG(const GPULayerID layerID, u16 *dstLineColor);
 
 	NDSDisplayID GetTargetDisplayByID() const;
-	void SetTargetDisplayByID(const NDSDisplayID theDisplayID);
+	NDSDisplay* GetTargetDisplay() const;
+	void SetTargetDisplay(NDSDisplay *theDisplay);
 	
 	GPUEngineID GetEngineID() const;
 	
-	virtual void SetupWorkingBuffers(NDSColorFormat requestedColorFormat, size_t w, size_t h);
-	void ResolveFramebufferToCustom(NDSDisplayInfo &mutableInfo);
-	template<NDSColorFormat OUTPUTFORMAT> void ResolveLinesDisplayedNative();
-	size_t GetLinesDisplayedNativeCount();
+	virtual void AllocateWorkingBuffers(NDSColorFormat requestedColorFormat, size_t w, size_t h);
 	
 	void REG_DISPx_pack_test();
 };
@@ -1670,7 +1663,7 @@ public:
 	void* GetCustomVRAMBlockPtr(const size_t blockID);
 	FragmentColor* Get3DFramebufferMain() const;
 	u16* Get3DFramebuffer16() const;
-	virtual void SetupWorkingBuffers(NDSColorFormat requestedColorFormat, size_t w, size_t h);
+	virtual void AllocateWorkingBuffers(NDSColorFormat requestedColorFormat, size_t w, size_t h);
 	
 	bool WillRender3DLayer();
 	bool WillCapture3DLayerDirect(const size_t l);
@@ -1707,11 +1700,23 @@ class NDSDisplay
 {
 private:
 	NDSDisplayID _ID;
-	GPUEngineBase *_gpu;
+	GPUEngineBase *_gpuEngine;
+	
+	// Native line tracking must be handled at the display level in order to account for
+	// games that use both engines for the same display. For example, "The Legend of Zelda:
+	// Phantom Hourglass" and "The Legend of Zelda: Spirit Tracks" can do this when the
+	// player moves the map to and from the touch screen.
+	bool _isLineDisplayNative[GPU_FRAMEBUFFER_NATIVE_HEIGHT];
+	size_t _nativeLineDisplayCount;
 	
 	u16 *_nativeBuffer16;
+	u32 *_workingNativeBuffer32;
 	void *_customBuffer;
 	
+	void *_renderedBuffer;
+ 	size_t _renderedWidth;
+ 	size_t _renderedHeight;
+	
 	void __constructor(const NDSDisplayID displayID, GPUEngineBase *theEngine);
 	
 public:
@@ -1719,15 +1724,30 @@ public:
 	NDSDisplay(const NDSDisplayID displayID);
 	NDSDisplay(const NDSDisplayID displayID, GPUEngineBase *theEngine);
 	
+	NDSDisplayID GetDisplayID() const;
+	
 	GPUEngineBase* GetEngine();
 	void SetEngine(GPUEngineBase *theEngine);
 	
 	GPUEngineID GetEngineID();
 	void SetEngineByID(const GPUEngineID theID);
 	
+	size_t GetNativeLineCount();
+ 	bool GetIsLineNative(const size_t l);
+ 	void SetIsLineNative(const size_t l, const bool isNative);
+ 	void ClearAllLinesToNative();
+	template<NDSColorFormat OUTPUTFORMAT> void ResolveLinesDisplayedNative();
+	void ResolveFramebufferToCustom(NDSDisplayInfo &mutableInfo);
+	bool DidPerformCustomRender() const;
+	
 	u16* GetNativeBuffer16() const;
+	u32* GetWorkingNativeBuffer32() const;
 	void* GetCustomBuffer() const;
-	void SetDrawBuffers(u16 *nativeBuffer16, void *customBuffer);
+	void SetDrawBuffers(u16 *nativeBuffer16, u32 *workingNativeBuffer32, void *customBuffer);
+	
+	void* GetRenderedBuffer() const;
+ 	size_t GetRenderedWidth() const;
+ 	size_t GetRenderedHeight() const;
 };
 
 class GPUEventHandler
@@ -1787,6 +1807,7 @@ private:
 	void *_customVRAMBlank;
 	
 	void *_masterFramebuffer;
+	u32 *_masterWorkingNativeBuffer32;
 	
 	NDSDisplayInfo _displayInfo;
 	
@@ -1858,17 +1879,17 @@ public:
 	void SetWillPostprocessDisplays(const bool willPostprocess);
 	void PostprocessDisplay(const NDSDisplayID displayID, NDSDisplayInfo &mutableInfo);
 	
-	// Normally, the GPUs will automatically resolve their native buffers to the master
+	// Normally, the displays will automatically resolve their native buffers to the master
 	// custom framebuffer at the end of V-blank so that all rendered graphics are contained
 	// within a single common buffer. This is necessary for when someone wants to read
 	// the NDS framebuffers, but the reader can only read a single buffer at a time.
-	// Certain functions, such as taking screenshots, as well as many frontends running
+	// Certain functions, such as taking screenshots, as well as many clients running
 	// the NDS video displays, require that they read from only a single buffer.
 	//
-	// However, if SetWillAutoResolveToCustomBuffer() is passed "false", then the frontend
+	// However, if SetWillAutoResolveToCustomBuffer() is passed "false", then the client
 	// becomes responsible for calling GetDisplayInfo() and reading the native and custom buffers
 	// properly for each display. If a single buffer is still needed for certain cases, then the
-	// frontend must manually call ResolveDisplayToCustomFramebuffer() for each display before
+	// client must manually call ResolveDisplayToCustomFramebuffer() for each display before
 	// reading the master custom framebuffer.
 	bool GetWillAutoResolveToCustomBuffer() const;
 	void SetWillAutoResolveToCustomBuffer(const bool willAutoResolve);