From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 31 Jan 2021 15:19:42 +0000 (+0200)
Subject: Register image loaders more explicitly
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=d3bc6c9;p=libs%2Fgui.git

Register image loaders more explicitly

The automatic registration just doesn't work reliably enough; there was
already a hack to work around the problems, so might as well make that
the official way.
---

diff --git a/source/graphics/bmploader.h b/source/graphics/bmploader.h
index db9af1d..273e104 100644
--- a/source/graphics/bmploader.h
+++ b/source/graphics/bmploader.h
@@ -6,7 +6,7 @@
 namespace Msp {
 namespace Graphics {
 
-class BmpLoader: public RegisteredImageLoader<BmpLoader>
+class BmpLoader: public ImageLoader
 {
 private:
 	IO::Base &io;
diff --git a/source/graphics/devil/devilloader.h b/source/graphics/devil/devilloader.h
index e94a31b..42ac2b2 100644
--- a/source/graphics/devil/devilloader.h
+++ b/source/graphics/devil/devilloader.h
@@ -6,7 +6,7 @@
 namespace Msp {
 namespace Graphics {
 
-class DevilLoader: public RegisteredImageLoader<DevilLoader>
+class DevilLoader: public ImageLoader
 {
 private:
 	IO::Base &io;
diff --git a/source/graphics/imageloader.cpp b/source/graphics/imageloader.cpp
index 965c7b3..da89798 100644
--- a/source/graphics/imageloader.cpp
+++ b/source/graphics/imageloader.cpp
@@ -21,8 +21,6 @@ using namespace std;
 namespace Msp {
 namespace Graphics {
 
-bool ImageLoader::registered_loaders_changed = false;
-
 ImageLoader::ImageLoader():
 	source(0)
 { }
@@ -49,36 +47,22 @@ ImageLoader *ImageLoader::open_file(const string &fn)
 
 ImageLoader *ImageLoader::open_io(IO::Seekable &io)
 {
-	(void)RegisteredImageLoader<BmpLoader>::reg;
-#ifdef WITH_LIBPNG
-	(void)RegisteredImageLoader<PngLoader>::reg;
-#endif
-#ifdef WITH_LIBJPEG
-	(void)RegisteredImageLoader<JpegLoader>::reg;
-#endif
-#ifdef WITH_DEVIL
-	(void)RegisteredImageLoader<DevilLoader>::reg;
-#endif
-#ifdef WITH_QUARTZ
-	(void)RegisteredImageLoader<QuartzLoader>::reg;
-#endif
-
-	list<RegisterBase *> &loaders = get_registered_loaders();
-	if(registered_loaders_changed)
+	Registry &registry = get_registry();
+	if(registry.changed)
 	{
-		registered_loaders_changed = false;
-		loaders.sort(signature_size_compare);
+		registry.changed = false;
+		registry.loaders.sort(signature_size_compare);
 	}
 
-	if(loaders.empty())
+	if(registry.loaders.empty())
 		throw unsupported_image_format("no loaders");
 
-	vector<char> sig_buf(loaders.back()->get_signature_size());
+	vector<char> sig_buf(registry.loaders.back()->get_signature_size());
 	unsigned sig_len = io.read(&sig_buf[0], sig_buf.size());
 	string signature(sig_buf.begin(), sig_buf.end());
 
 	ImageLoader *loader = 0;
-	for(list<RegisterBase *>::const_iterator i=loaders.begin(); (!loader && i!=loaders.end()); ++i)
+	for(list<RegisterBase *>::const_iterator i=registry.loaders.begin(); (!loader && i!=registry.loaders.end()); ++i)
 		if((*i)->detect(signature))
 			loader = (*i)->create(io);
 
@@ -99,18 +83,34 @@ ImageLoader *ImageLoader::open_io(IO::Seekable &io)
 	return loader;
 }
 
-
-ImageLoader::RegisterBase::RegisterBase()
+void ImageLoader::load(Image::Data &data)
 {
-	get_registered_loaders().push_back(this);
-	registered_loaders_changed = true;
+	load_headers(data);
+	load_data(data);
 }
 
-
-list<ImageLoader::RegisterBase *> &ImageLoader::get_registered_loaders()
+ImageLoader::Registry &ImageLoader::get_registry()
 {
-	static list<RegisterBase *> regs;
-	return regs;
+	static Registry registry;
+	static bool initialized = false;
+	if(!initialized)
+	{
+		initialized = true;
+		register_loader<BmpLoader>();
+#ifdef WITH_LIBPNG
+		register_loader<PngLoader>();
+#endif
+#ifdef WITH_LIBJPEG
+		register_loader<JpegLoader>();
+#endif
+#ifdef WITH_DEVIL
+		register_loader<DevilLoader>();
+#endif
+#ifdef WITH_QUARTZ
+		register_loader<QuartzLoader>();
+#endif
+	}
+	return registry;
 }
 
 bool ImageLoader::signature_size_compare(RegisterBase *r1, RegisterBase *r2)
@@ -118,5 +118,16 @@ bool ImageLoader::signature_size_compare(RegisterBase *r1, RegisterBase *r2)
 	return r1->get_signature_size()<r2->get_signature_size();
 }
 
+
+ImageLoader::Registry::Registry():
+	changed(false)
+{ }
+
+ImageLoader::Registry::~Registry()
+{
+	for(list<RegisterBase *>::iterator i=loaders.begin(); i!=loaders.end(); ++i)
+		delete *i;
+}
+
 } // namespace Graphics
 } // namespace Msp
diff --git a/source/graphics/imageloader.h b/source/graphics/imageloader.h
index 031ecb4..f0b8d52 100644
--- a/source/graphics/imageloader.h
+++ b/source/graphics/imageloader.h
@@ -27,7 +27,7 @@ protected:
 	class RegisterBase
 	{
 	protected:
-		RegisterBase();
+		RegisterBase() { }
 	public:
 		virtual ~RegisterBase() { }
 
@@ -36,13 +36,27 @@ protected:
 		virtual ImageLoader *create(IO::Seekable &) const = 0;
 	};
 
+	template<typename T>
+	class RegisteredLoader: public RegisterBase
+	{
+	public:
+		virtual unsigned get_signature_size() const { return T::get_signature_size(); }
+		virtual bool detect(const std::string &s) const { return T::detect(s); }
+		virtual ImageLoader *create(IO::Seekable &io) const { return new T(io); }
+	};
+
+	struct Registry
+	{
+		std::list<RegisterBase *> loaders;
+		bool changed;
+
+		Registry();
+		~Registry();
+	};
+
 private:
 	IO::Base *source;
 
-	static std::list<RegisterBase *> &get_registered_loaders();
-	static bool registered_loaders_changed;
-	static bool signature_size_compare(RegisterBase *, RegisterBase *);
-
 protected:
 	ImageLoader();
 public:
@@ -51,32 +65,25 @@ public:
 	static ImageLoader *open_file(const std::string &);
 	static ImageLoader *open_io(IO::Seekable &);
 
-	virtual void load(Image::Data &) = 0;
-};
-
-
-template<typename T>
-class RegisteredImageLoader: public ImageLoader
-{
-	friend class ImageLoader;
+	virtual void load(Image::Data &);
+	virtual void load_headers(Image::Data &) { }
+	virtual void load_data(Image::Data &) { }
 
+	template<typename T>
+	static void register_loader();
 private:
-	class Register: public RegisterBase
-	{
-	public:
-		virtual unsigned get_signature_size() const { return T::get_signature_size(); }
-		virtual bool detect(const std::string &s) const { return T::detect(s); }
-		virtual ImageLoader *create(IO::Seekable &io) const { return new T(io); }
-	};
-
-	static Register reg;
+	static Registry &get_registry();
 
-protected:
-	RegisteredImageLoader() { (void)reg; }
+	static bool signature_size_compare(RegisterBase *, RegisterBase *);
 };
 
 template<typename T>
-typename RegisteredImageLoader<T>::Register RegisteredImageLoader<T>::reg;
+void ImageLoader::register_loader()
+{
+	Registry &registry = get_registry();
+	registry.loaders.push_back(new RegisteredLoader<T>);
+	registry.changed = true;
+}
 
 } // namespace Graphics
 } // namespace Msp
diff --git a/source/graphics/jpeg/jpegloader.h b/source/graphics/jpeg/jpegloader.h
index b93d5bc..04e8917 100644
--- a/source/graphics/jpeg/jpegloader.h
+++ b/source/graphics/jpeg/jpegloader.h
@@ -6,7 +6,7 @@
 namespace Msp {
 namespace Graphics {
 
-class JpegLoader: public RegisteredImageLoader<JpegLoader>
+class JpegLoader: public ImageLoader
 {
 private:
 	struct Private;
diff --git a/source/graphics/png/pngloader.h b/source/graphics/png/pngloader.h
index de8b535..6ed57cc 100644
--- a/source/graphics/png/pngloader.h
+++ b/source/graphics/png/pngloader.h
@@ -6,7 +6,7 @@
 namespace Msp {
 namespace Graphics {
 
-class PngLoader: public RegisteredImageLoader<PngLoader>
+class PngLoader: public ImageLoader
 {
 private:
 	struct Private;
diff --git a/source/graphics/quartz/quartzloader.h b/source/graphics/quartz/quartzloader.h
index 963e45c..4885ff5 100644
--- a/source/graphics/quartz/quartzloader.h
+++ b/source/graphics/quartz/quartzloader.h
@@ -6,7 +6,7 @@
 namespace Msp {
 namespace Graphics {
 
-class QuartzLoader: public RegisteredImageLoader<QuartzLoader>
+class QuartzLoader: public ImageLoader
 {
 private:
 	struct Private;