Implement the standard set of copy and move operations for Surface

src/surface.cpp

@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <cassert>
 #include <iomanip>
+#include <utility>
 
 using namespace std;
 
@@ -94,22 +95,44 @@ Surface::Surface(SDL_Surface *raw_, bool freeWhenDone_)
 {
 }
 
-Surface::Surface(Surface *s) {
+Surface::Surface(Surface const& other)
-	raw = SDL_ConvertSurface(s->raw, s->raw->format, SDL_SWSURFACE);
+	: Surface(SDL_ConvertSurface(
+			other.raw, other.raw->format, SDL_SWSURFACE), true)
+{
 	// Note: A bug in SDL_ConvertSurface() leaves the per-surface alpha
 	//       undefined when converting from RGBA to RGBA. This can cause
 	//       problems if the surface is later converted to a format without
 	//       an alpha channel, such as the display format.
-	raw->format->alpha = s->raw->format->alpha;
+	raw->format->alpha = other.raw->format->alpha;
-	freeWhenDone = true;
 }
 
-Surface::~Surface() {
+Surface::Surface(Surface&& other)
+	: raw(other.raw)
+	, freeWhenDone(other.freeWhenDone)
+{
+	other.raw = nullptr;
+	other.freeWhenDone = false;
+}
+
+Surface::~Surface()
+{
 	if (freeWhenDone) {
 		SDL_FreeSurface(raw);
 	}
 }
 
+Surface& Surface::operator=(Surface other)
+{
+	swap(other);
+	return *this;
+}
+
+void Surface::swap(Surface& other)
+{
+	std::swap(raw, other.raw);
+	std::swap(freeWhenDone, other.freeWhenDone);
+}
+
 void Surface::convertToDisplayFormat() {
 	SDL_Surface *newSurface = SDL_DisplayFormat(raw);
 	if (newSurface) {

src/surface.h

@@ -52,8 +52,14 @@ public:
 	static Surface *loadImage(const std::string &img,
 			const std::string &skin="", bool loadAlpha=true);
 
-	Surface(Surface *s);
+	// TODO: Remove this once naked Surface pointers are no longer in use.
+	Surface(Surface *other) : Surface(*other) {}
+
+	Surface(Surface const& other);
+	Surface(Surface&& other);
 	~Surface();
+	Surface& operator=(Surface other);
+	void swap(Surface& other);
 
 	/** Converts the underlying surface to the same pixel format as the frame
 	  * buffer, for faster blitting. This removes the alpha channel if the