kc3-lang/ftgl/docs/FTGL.txt

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• Author : henry
  Date : 2001-11-05 20:58:07
  Hash : 8621b34b
  Message : More words of wisdom

• docs/FTGL.txt

• FTGL User Guide
  (work in progress)
  
  Introduction
  
  OpenGL doesn't provide direct font support, so the application must use any of OpenGL's other features for font rendering, such as drawing bitmaps or pixmaps, creating texture maps containing an entire character set, drawing character outlines, or creating 3D geometry for each character.
  
  
  One thing all of these systems have in commen is they require a pre-processing stage to take the native fonts and convert them into proprietry format.
  
  FTGL was borne out of the need to treat fonts in openGL applications just like any other application. For example when using Photoshop you don't need an intermediate pre-processing step to use high quality scalable fonts.
  
  Choosing a font type
  FTGL supports 5 font output types in 3 groups, raster fonts, vector fonts and texure fonts which are a mixture of both. Each font type has it's advantages and disadvantages
  
  The two raster types are
  -  Bitmapped
  -  Antialiased pixmapped
  
  
  
  
  The vector types are
  -  Outline
  -  Polygonal
  
  
  
  
  -  Texture mapped
  This is probably the most versatile type. It is fast, antialised and can be transformed just like any openGL primitive.
  
  Creating a font
  
  	FTGLPixmapFont font;
  	
  	font.Open( "Fonts:Arial");
  	font.FaceSize( 72);
  	
  	font.render( "Hello World!");
  
  	FTFont::Open( string, cache);
  	const char* string;	
  	bool cache;			
  
  A side effect of this is you can specify a sub set of glyphs to be pre-loaded. This will let you use larger higher quality glyphs without consuming huge amounts of ram as you would if you laoded the entire font. For example if your application only needs numbers, eg for scores, you can use the following code to preload them.
  
  	// Open the font with pre-cache set to false
  	font.Open( "Fonts:Arial", false);
  	
  	// Set the size
  	font.FaceSize( 72);
  	
  	// Cause the font to preload the number chars without rendering them.
  	font.Advance( "0123456789");
  
  
  
  More font commands
  
  
  
  
  Specifying a character map encoding.
  
  From the freetype docs...
  "By default, when a new face object is created, (freetype) lists all the charmaps contained in the font face and selects the one that supports Unicode character codes if it finds one. Otherwise, it tries to find support for Latin-1, then ASCII."
  
  It then gives up. In this case FTGL will set the charmap to the first it finds in the fonts charmap list.
  
  You can expilcitly set the char encoding with Charmap:
  	bool FTFont::CharMap( encoding);
  	FT_Encoding encoding;	Freetype code
  	
  for example...
  font.CharMap( ft_encoding_apple_roman);
  
  Valid encodings as at Freetype 2.0.4
  	ft_encoding_none
  	ft_encoding_symbol
  	ft_encoding_unicode
  	ft_encoding_latin_2
  	ft_encoding_sjis
  	ft_encoding_gb2312
  	ft_encoding_big5
  	ft_encoding_wansung
  	ft_encoding_johab
  	ft_encoding_adobe_standard
  	ft_encoding_adobe_expert
  	ft_encoding_adobe_custom
  	ft_encoding_apple_roman
  
  This will return an error if the requested encoding can't be found in the font.
  
  
  
  FAQ
  
  Sample font manager class.
  
  FTGLTextureFont* myFont = FTGLFontManager::Instance().GetFont( "arial.ttf", 72);
  
  #include	<map>
  #include	"FTGLTextureFont.h"
  
  using namespace std;
  
  typedef map< string, FTFont*> FontList;
  typedef FontList::const_iterator FontIter;
  
  class FTGLFontManager
  {
  	public:
  		static FTGLFontManager& Instance()
  		{
  			static FTGLFontManager tm;
  			return tm;
  		}
  		
  		~FTGLFontManager()
  		{
      		FontIter font;
  		    for( font = fonts.begin(); font != fonts.end(); font++)
      		{
      		    delete (*font).second;;
  		    }
      
  			fonts.clear();
  		}
  
  		
  		FTFont* GetFont( const char *filename, int size)
  		{
  			char buf[256];
  			sprintf(buf, "%s%i", filename, size);
  			string fontKey = string(buf);
  			
  			FontIter result = fonts.find( fontKey);
  			if( result != fonts.end())
  			{
  				LOGMSG( "Found font %s in list", filename);
  				return result->second;
  			}
  		
  			FTFont* font = new FTGLTextureFont;
  			
  			string fullname = path + string( filename);
  			
  			if( !font->Open( fullname.c_str()))
  			{
  				LOGERROR( "Font %s failed to open", fullname.c_str());
  				return NULL;
  			}
  			
  			if( !font->FaceSize( size))
  			{
  				LOGERROR( "Font %s failed to set size %i", filename, size);
  				return NULL;
  			}
  		
  			fonts[fontKey] = font;
  			
  			return font;
  		
  		}
  	
  		
  	private:
  		// Hide these 'cause this is a singleton.
  		FTGLFontManager(){}
  		FTGLFontManager( const FTGLFontManager&){};
  		FTGLFontManager& operator = ( const FTGLFontManager&){ return *this;};
  		
  		// container for fonts
  		FontList fonts;
  	
  };