Enable conditional compilation for PNG support. Some ports (libretro) don't need it at all.

Changes.txt

@@ -59,6 +59,9 @@
 
   * Fixed 'Dancing Plate (Unknown) (PAL)' to use joystick.
 
+  * PNG image support is now conditionally compiled into Stella.  All
+    major ports (Linux/macOS/Windows) have it enabled by default.
+
 -Have fun!
 
 

configure

@@ -22,6 +22,7 @@ _build_sound=yes
 _build_debugger=yes
 _build_joystick=yes
 _build_cheats=yes
+_build_png=yes
 _build_static=no
 _build_profile=no
 _build_debug=no
@@ -198,6 +199,8 @@ Optional Features:
   --disable-joystick
   --enable-cheats        enable/disable cheatcode support [enabled]
   --disable-cheats
+  --enable-png           enable/disable PNG image support [enabled]
+  --disable-png
   --enable-windowed      enable/disable windowed rendering modes [enabled]
   --disable-windowed
   --enable-shared        build shared binary [enabled]
@@ -237,6 +240,8 @@ for ac_option in $@; do
       --disable-joystick)       _build_joystick=no   ;;
       --enable-cheats)          _build_cheats=yes    ;;
       --disable-cheats)         _build_cheats=no     ;;
+      --enable-png)             _build_png=yes       ;;
+      --disable-png)            _build_png=no        ;;
       --enable-windowed)        _build_windowed=yes  ;;
       --disable-windowed)       _build_windowed=no   ;;
       --enable-shared)          _build_static=no     ;;
@@ -669,6 +674,14 @@ else
 	echo
 fi
 
+if test "$_build_png" = yes ; then
+	echo_n "   PNG image support enabled"
+	echo
+else
+	echo_n "   PNG image support disabled"
+	echo
+fi
+
 if test "$_build_windowed" = "yes" ; then
 	echo_n "   Windowed rendering modes enabled"
 	echo
@@ -802,6 +815,10 @@ if test "$_build_cheats" = yes ; then
 	INCLUDES="$INCLUDES -I$CHEAT"
 fi
 
+if test "$_build_png" = yes ; then
+	DEFINES="$DEFINES -DPNG_SUPPORT"
+fi
+
 if test "$_build_profile" = no ; then
 	_build_profile=
 fi

src/common/PKeyboardHandler.cxx

@@ -546,9 +546,11 @@ bool PhysicalKeyboardHandler::handleAltEvent(StellaKey key, StellaMod mod, bool
           myOSystem.state().toggleTimeMachine();
           break;
 
+    #ifdef PNG_SUPPORT
         case KBDK_S:
           myOSystem.png().toggleContinuousSnapshots(StellaModTest::isShift(mod));
           break;
+    #endif
 
         default:
           handled = false;

src/common/PNGLibrary.cxx

@@ -15,6 +15,8 @@
 // this file, and for a DISCLAIMER OF ALL WARRANTIES.
 //============================================================================
 
+#if defined(PNG_SUPPORT)
+
 #include <cmath>
 
 #include "bspf.hxx"
@@ -493,3 +495,5 @@ void PNGLibrary::png_user_error(png_structp ctx, png_const_charp str)
 PNGLibrary::ReadInfoType PNGLibrary::ReadInfo = {
   nullptr, nullptr, 0, 0, 0, 0, 0
 };
+
+#endif  // PNG_SUPPORT

src/common/PNGLibrary.hxx

@@ -18,6 +18,8 @@
 #ifndef PNGLIBRARY_HXX
 #define PNGLIBRARY_HXX
 
+#if defined(PNG_SUPPORT)
+
 #include <png.h>
 
 class OSystem;
@@ -197,4 +199,6 @@ class PNGLibrary
     PNGLibrary& operator=(PNGLibrary&&) = delete;
 };
 
+#endif  // PNG_SUPPORT
+
 #endif

src/debugger/gui/TiaOutputWidget.cxx

@@ -61,9 +61,10 @@ void TiaOutputWidget::loadConfig()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TiaOutputWidget::saveSnapshot(int execDepth, const string& execPrefix)
 {
-  if (execDepth > 0) {
+#ifdef PNG_SUPPORT
+  if(execDepth > 0)
     drawWidget(false);
-  }
+
   ostringstream sspath;
   sspath << instance().snapshotSaveDir()
          << instance().console().properties().get(PropType::Cart_Name);
@@ -93,6 +94,9 @@ void TiaOutputWidget::saveSnapshot(int execDepth, const string& execPrefix)
   if (execDepth == 0) {
     instance().frameBuffer().showMessage(message);
   }
+#else
+  instance().frameBuffer().showMessage("PNG image saving not supported");
+#endif
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/emucore/EventHandler.cxx

@@ -118,7 +118,9 @@ void EventHandler::reset(EventHandlerState state)
 {
   setState(state);
   myOSystem.state().reset();
+#ifdef PNG_SUPPORT
   myOSystem.png().setContinuousSnapInterval(0);
+#endif
 
   // Reset events almost immediately after starting emulation mode
   // We wait a little while (0.5s), since 'hold' events may be present,
@@ -219,9 +221,11 @@ void EventHandler::poll(uInt64 time)
       cheat->evaluate();
   #endif
 
+  #ifdef PNG_SUPPORT
     // Handle continuous snapshots
     if(myOSystem.png().continuousSnapEnabled())
       myOSystem.png().updateTime(time);
+  #endif
   }
   else if(myOverlay)
   {

src/emucore/OSystem.cxx

@@ -83,6 +83,9 @@ OSystem::OSystem()
   #ifdef CHEATCODE_SUPPORT
     myFeatures += "Cheats ";
   #endif
+  #ifdef PNG_SUPPORT
+    myFeatures += "PNG";
+  #endif
 
   // Get build info
   ostringstream info;
@@ -154,8 +157,10 @@ bool OSystem::create()
   // Create random number generator
   myRandom = make_unique<Random>(uInt32(TimerManager::getTicks()));
 
+#ifdef PNG_SUPPORT
   // Create PNG handler
   myPNGLib = make_unique<PNGLibrary>(*this);
+#endif
 
   return true;
 }

src/emucore/OSystem.hxx

@@ -18,6 +18,9 @@
 #ifndef OSYSTEM_HXX
 #define OSYSTEM_HXX
 
+#ifdef PNG_SUPPORT
+class PNGLibrary;
+#endif
 #ifdef CHEATCODE_SUPPORT
 class CheatManager;
 #endif
@@ -29,7 +32,6 @@ class Menu;
 class TimeMachine;
 class FrameBuffer;
 class EventHandler;
-class PNGLibrary;
 class Properties;
 class PropertiesSet;
 class Random;
@@ -173,13 +175,6 @@ class OSystem
     */
     TimerManager& timer() const { return *myTimerManager; }
 
-    /**
-      Get the PNG handler of the system.
-
-      @return The PNGlib object
-    */
-    PNGLibrary& png() const { return *myPNGLib; }
-
     /**
       This method should be called to initiate the process of loading settings
       from the config file.  It takes care of loading settings, applying
@@ -212,6 +207,15 @@ class OSystem
     CheatManager& cheat() const { return *myCheatManager; }
 #endif
 
+#ifdef PNG_SUPPORT
+    /**
+      Get the PNG handler of the system.
+
+      @return The PNGlib object
+    */
+    PNGLibrary& png() const { return *myPNGLib; }
+#endif
+
     /**
       Set all config file paths for the OSystem.
     */
@@ -491,15 +495,17 @@ class OSystem
     unique_ptr<CheatManager> myCheatManager;
   #endif
 
+  #ifdef PNG_SUPPORT
+    // PNG object responsible for loading/saving PNG images
+    unique_ptr<PNGLibrary> myPNGLib;
+  #endif
+
     // Pointer to the StateManager object
     unique_ptr<StateManager> myStateManager;
 
     // Pointer to the TimerManager object
     unique_ptr<TimerManager> myTimerManager;
 
-    // PNG object responsible for loading/saving PNG images
-    unique_ptr<PNGLibrary> myPNGLib;
-
     // The list of log messages
     string myLogMessages;
 

src/emucore/TIASurface.cxx

@@ -398,7 +398,9 @@ void TIASurface::render()
   if(mySaveSnapFlag)
   {
     mySaveSnapFlag = false;
+  #ifdef PNG_SUPPORT
     myOSystem.png().takeSnapshot();
+  #endif
   }
 }
 

src/gui/RomInfoWidget.cxx

@@ -95,9 +95,10 @@ void RomInfoWidget::parseProperties(const FilesystemNode& node)
 
   // Initialize to empty properties entry
   mySurfaceErrorMsg = "";
-  mySurfaceIsValid = true;
+  mySurfaceIsValid = false;
   myRomInfo.clear();
 
+#ifdef PNG_SUPPORT
   // Get a valid filename representing a snapshot file for this rom
   const string& filename = instance().snapshotLoadDir() +
       myProperties.get(PropType::Cart_Name) + ".png";
@@ -111,12 +112,15 @@ void RomInfoWidget::parseProperties(const FilesystemNode& node)
     const GUI::Rect& src = mySurface->srcRect();
     float scale = std::min(float(myAvail.w) / src.width(), float(myAvail.h) / src.height());
     mySurface->setDstSize(uInt32(src.width() * scale), uInt32(src.height() * scale));
+    mySurfaceIsValid = true;
   }
   catch(const runtime_error& e)
   {
-    mySurfaceIsValid = false;
     mySurfaceErrorMsg = e.what();
   }
+#else
+  mySurfaceErrorMsg = "PNG image loading not supported";
+#endif
   if(mySurface)
     mySurface->setVisible(mySurfaceIsValid);