First pass at conditional compilation of SDL for Stella.

For now, it's enabled for all mainline ports.
Stella doesn't absolutely need SDL (as the libretro port shows); it's less than 2000 lines in 220,000+ LOC,

Makefile

@@ -26,7 +26,7 @@
 
 srcdir      ?= .
 
-DEFINES     := -D_GLIBCXX_USE_CXX11_ABI=1
+DEFINES     := -DSDL_SUPPORT -D_GLIBCXX_USE_CXX11_ABI=1
 LDFLAGS     := -pthread
 INCLUDES    :=
 LIBS	    :=

src/common/MediaFactory.hxx

@@ -19,7 +19,9 @@
 #define MEDIA_FACTORY_HXX
 
 #include "bspf.hxx"
+#if defined(SDL_SUPPORT)
   #include "SDL_lib.hxx"
+#endif
 
 #include "OSystem.hxx"
 #include "Settings.hxx"
@@ -54,16 +56,20 @@
 #if defined(__LIB_RETRO__)
   #include "EventHandlerLIBRETRO.hxx"
   #include "FrameBufferLIBRETRO.hxx"
-#else
+#elif defined(SDL_SUPPORT)
   #include "EventHandlerSDL2.hxx"
   #include "FrameBufferSDL2.hxx"
+#else
+  #error Unsupported backend!
 #endif
 
 #if defined(SOUND_SUPPORT)
   #if defined(__LIB_RETRO__)
     #include "SoundLIBRETRO.hxx"
-  #else
+  #elif defined(SDL_SUPPORT)
     #include "SoundSDL2.hxx"
+  #else
+    #include "SoundNull.hxx"
   #endif
 #else
   #include "SoundNull.hxx"
@@ -140,18 +146,22 @@ class MediaFactory
     {
     #if defined(__LIB_RETRO__)
       return make_unique<FrameBufferLIBRETRO>(osystem);
-    #else
+    #elif defined(SDL_SUPPORT)
       return make_unique<FrameBufferSDL2>(osystem);
+    #else
+      #error Unsupported platform for FrameBuffer!
     #endif
     }
 
     static unique_ptr<Sound> createAudio(OSystem& osystem, AudioSettings& audioSettings)
     {
-    #ifdef SOUND_SUPPORT
+    #if defined(SOUND_SUPPORT)
       #if defined(__LIB_RETRO__)
         return make_unique<SoundLIBRETRO>(osystem, audioSettings);
-      #elif defined(SOUND_SUPPORT)
+      #elif defined(SOUND_SUPPORT) && defined(SDL_SUPPORT)
         return make_unique<SoundSDL2>(osystem, audioSettings);
+      #else
+        return make_unique<SoundNull>(osystem);
       #endif
     #else
       return make_unique<SoundNull>(osystem);
@@ -162,24 +172,27 @@ class MediaFactory
     {
     #if defined(__LIB_RETRO__)
       return make_unique<EventHandlerLIBRETRO>(osystem);
-	#else
+    #elif defined(SDL_SUPPORT)
       return make_unique<EventHandlerSDL2>(osystem);
+    #else
+      #error Unsupported platform for EventHandler!
     #endif
     }
 
     static void cleanUp()
     {
+    #if defined(SDL_SUPPORT)
       SDL_Quit();
+    #endif
     }
 
     static string backendName()
     {
-      ostringstream buf;
+    #if defined(SDL_SUPPORT)
-      SDL_version ver;
+      return SDLVersion();
-      SDL_GetVersion(&ver);
+    #else
-      buf << "SDL " << int(ver.major) << "." << int(ver.minor) << "." << int(ver.patch);
+      return "Custom backend";
-
+    #endif
-      return buf.str();
     }
 
   private:

src/common/SDL_lib.hxx

@@ -18,6 +18,8 @@
 #ifndef SDL_LIB_HXX
 #define SDL_LIB_HXX
 
+#include "bspf.hxx"
+
 /*
  * We can't control the quality of code from outside projects, so for now
  * just disable warnings for it.
@@ -43,4 +45,13 @@
 #undef pixel
 #undef bool
 
-#endif
+static inline string SDLVersion()
+{
+  ostringstream buf;
+  SDL_version ver;
+  SDL_GetVersion(&ver);
+  buf << "SDL " << int(ver.major) << "." << int(ver.minor) << "." << int(ver.patch);
+  return buf.str();
+}
+
+#endif  // SDL_LIB_HXX

src/common/StellaKeys.hxx

@@ -18,7 +18,9 @@
 #ifndef STELLA_KEYS_HXX
 #define STELLA_KEYS_HXX
 
+#ifdef SDL_SUPPORT
   #include "SDL_lib.hxx"
+#endif
 
 /**
   This class implements a thin wrapper around the SDL keysym enumerations,
@@ -439,7 +441,11 @@ namespace StellaKeyName
 {
   inline const char* const forKey(StellaKey key)
   {
+  #ifdef SDL_SUPPORT
     return SDL_GetScancodeName(SDL_Scancode(key));
+  #else
+    return "";
+  #endif
   }
 };
 

src/macos/stella.xcodeproj/project.pbxproj

@@ -3026,6 +3026,7 @@
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
 				GCC_OPTIMIZATION_LEVEL = 0;
 				GCC_PREPROCESSOR_DEFINITIONS = (
+					SDL_SUPPORT,
 					CHEATCODE_SUPPORT,
 					DEBUGGER_SUPPORT,
 					JOYSTICK_SUPPORT,
@@ -3080,6 +3081,7 @@
 				GCC_GENERATE_DEBUGGING_SYMBOLS = NO;
 				GCC_OPTIMIZATION_LEVEL = 3;
 				GCC_PREPROCESSOR_DEFINITIONS = (
+					SDL_SUPPORT,
 					CHEATCODE_SUPPORT,
 					DEBUGGER_SUPPORT,
 					JOYSTICK_SUPPORT,

src/windows/Stella.vcxproj

@@ -157,7 +157,7 @@
     <ClCompile>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;DEBUG_BUILD;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;DEBUG_BUILD;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <MinimalRebuild>false</MinimalRebuild>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
@@ -193,7 +193,7 @@
     <ClCompile>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;DEBUG_BUILD;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;DEBUG_BUILD;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <MinimalRebuild>false</MinimalRebuild>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
@@ -226,7 +226,7 @@
       <OmitFramePointers>true</OmitFramePointers>
       <WholeProgramOptimization>false</WholeProgramOptimization>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <RuntimeTypeInfo>false</RuntimeTypeInfo>
       <PrecompiledHeader>
@@ -260,7 +260,7 @@
       <OmitFramePointers>true</OmitFramePointers>
       <WholeProgramOptimization>false</WholeProgramOptimization>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <RuntimeTypeInfo>false</RuntimeTypeInfo>
       <PrecompiledHeader>
@@ -298,7 +298,7 @@
       <InlineFunctionExpansion>AnySuitable</InlineFunctionExpansion>
       <OmitFramePointers>true</OmitFramePointers>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <RuntimeTypeInfo>false</RuntimeTypeInfo>
       <PrecompiledHeader>
@@ -335,7 +335,7 @@
       <InlineFunctionExpansion>Default</InlineFunctionExpansion>
       <OmitFramePointers>true</OmitFramePointers>
       <AdditionalIncludeDirectories>..\yacc;..\emucore;..\emucore\tia;..\emucore\tia\frame-manager;..\common;..\common\tv_filters;..\gui;..\debugger\gui;..\debugger;..\windows;..\cheat;..\zlib;..\libpng;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>BSPF_WINDOWS;WIN32;NDEBUG;SDL_SUPPORT;PNG_SUPPORT;JOYSTICK_SUPPORT;DEBUGGER_SUPPORT;WINDOWED_SUPPORT;SOUND_SUPPORT;CHEATCODE_SUPPORT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <RuntimeTypeInfo>false</RuntimeTypeInfo>
       <PrecompiledHeader>