Refactor NDS and DSi to be objects (#1893)

* First crack at refactoring NDS and DSi into objects

- Remove all global/`static` variables in `NDS` and related classes
- Rely more on virtual dispatch when we need to pick methods at runtime
- Pass `NDS&` or `DSi&` to its constituent components where necessary
- Introduce some headers or move some definitions to break `#include` cycles

* Refactor the frontend to accommodate the core's changes

* Move up `SchedList`'s declaration

- Move it to before the components are initialized so the `map`s inside are initialized
- Fields in C++ are initialized in the order they're declared

* Fix a crash when allocating memory

* Fix JIT-free builds

* Fix GDB-free builds

* Fix Linux builds

- Explicitly qualify some member types in NDS, since they share the same name as their classes

* Remove an unnecessary template argument

- This was causing the build to fail on macOS

* Fix ARM and Android builds

* Rename `Constants.h` to `MemConstants.h`

* Add `NDS::IsRunning()`

* Use an `#include` guard instead of `#pragma once`

src/frontend/qt_sdl/AudioInOut.cpp

@@ -55,8 +55,9 @@ void AudioCallback(void* data, Uint8* stream, int len)
     s16 buf_in[1024*2];
     int num_in;
 
+    EmuThread* emuThread = (EmuThread*)data;
     SDL_LockMutex(audioSyncLock);
-    num_in = NDS::SPU->ReadOutput(buf_in, len_in);
+    num_in = emuThread->NDS->SPU.ReadOutput(buf_in, len_in);
     SDL_CondSignal(audioSync);
     SDL_UnlockMutex(audioSyncLock);
 
@@ -244,7 +245,7 @@ void MicLoadWav(const std::string& name)
     SDL_FreeWAV(buf);
 }
 
-void MicProcess()
+void MicProcess(melonDS::NDS& nds)
 {
     int type = Config::MicInputType;
     bool cmd = Input::HotkeyDown(HK_Mic);
@@ -257,16 +258,16 @@ void MicProcess()
     switch (type)
     {
     case micInputType_Silence: // no mic
-        Frontend::Mic_FeedSilence();
+        Frontend::Mic_FeedSilence(nds);
         break;
 
     case micInputType_External: // host mic
     case micInputType_Wav: // WAV
-        Frontend::Mic_FeedExternalBuffer();
+        Frontend::Mic_FeedExternalBuffer(nds);
         break;
 
     case micInputType_Noise: // blowing noise
-        Frontend::Mic_FeedNoise();
+        Frontend::Mic_FeedNoise(nds);
         break;
     }
 }
@@ -296,7 +297,7 @@ void SetupMicInputData()
     }
 }
 
-void Init()
+void Init(EmuThread* thread)
 {
     audioMuted = false;
     audioSync = SDL_CreateCond();
@@ -310,6 +311,7 @@ void Init()
     whatIwant.channels = 2;
     whatIwant.samples = 1024;
     whatIwant.callback = AudioCallback;
+    whatIwant.userdata = thread;
     audioDevice = SDL_OpenAudioDevice(NULL, 0, &whatIwant, &whatIget, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE);
     if (!audioDevice)
     {
@@ -349,12 +351,12 @@ void DeInit()
     micWavBuffer = nullptr;
 }
 
-void AudioSync()
+void AudioSync(NDS& nds)
 {
     if (audioDevice)
     {
         SDL_LockMutex(audioSyncLock);
-        while (NDS::SPU->GetOutputSize() > 1024)
+        while (nds.SPU.GetOutputSize() > 1024)
         {
             int ret = SDL_CondWaitTimeout(audioSync, audioSyncLock, 500);
             if (ret == SDL_MUTEX_TIMEDOUT) break;
@@ -363,11 +365,11 @@ void AudioSync()
     }
 }
 
-void UpdateSettings()
+void UpdateSettings(NDS& nds)
 {
     MicClose();
 
-    NDS::SPU->SetInterpolation(Config::AudioInterp);
+    nds.SPU.SetInterpolation(Config::AudioInterp);
     SetupMicInputData();
 
     MicOpen();