DolphinQt: Support banners in Homebrew Channel format

HBC uses files named icon.png for icons. This change makes Dolphin
support that file name, and also [executable file name].png
in case someone wants to have multiple files in one folder.

The HBC banner support is mainly intended for DOL and ELF files,
but it can also be used to override banners of disc images,
something that wasn't possible in the past.

That sure was simple compared to the wx version of this commit...

Source/Core/DolphinQt/GameList/GameFile.cpp

@@ -73,7 +73,8 @@ GameFile::GameFile(const QString& fileName)
     : m_file_name(fileName)
 {
 	QFileInfo info(m_file_name);
-	m_folder_name = info.absoluteDir().dirName();
+	QDir directory = info.absoluteDir();
+	m_folder_name = directory.dirName();
 
 	if (LoadFromCache())
 	{
@@ -140,6 +141,16 @@ GameFile::GameFile(const QString& fileName)
 		m_file_size = info.size();
 		m_platform = DiscIO::IVolume::ELF_DOL;
 	}
+
+	// PNG files can optionally be used as banners. Typical for DOLs and ELFs, but also works with
+	// volumes. icon.png is the file name used by Homebrew Channel. The ability to use a PNG file
+	// with the same name as the main file is provided as an alternative for those who want to have
+	// multiple files in one folder instead of having a Homebrew Channel-style folder structure.
+	QImage banner(directory.filePath(info.baseName() + SL(".png")));
+	if (banner.isNull())
+		banner.load(directory.filePath(SL("icon.png")));
+	if (!banner.isNull())
+		m_banner = QPixmap::fromImage(banner);
 }
 
 bool GameFile::LoadFromCache()
@@ -259,6 +270,7 @@ QString GameFile::CreateCacheFilename() const
 	return fullname;
 }
 
+// Outputs to m_banner
 void GameFile::ReadBanner(const DiscIO::IVolume& volume)
 {
 	int width, height;

Source/Core/DolphinQt/GameList/GameFile.h

@@ -81,5 +81,6 @@ private:
 	bool IsElfOrDol() const;
 	QString CreateCacheFilename() const;
 
+	// Outputs to m_banner
 	void ReadBanner(const DiscIO::IVolume& volume);
 };