GRAPHICS/GUI: Implement kerning support for Font.

This adapts the related graphics code, which is the generic Font API and the
TTF font implementation.

It furthermore adapts the GUI to properly take care of kerning in text input
widgets.

1 files changed, 31 insertions, 6 deletions

diff --git a/graphics/fonts/ttf.cpp b/graphics/fonts/ttf.cpp
index 8a6b87c000..b5bf5c0158 100644
--- a/graphics/fonts/ttf.cpp
+++ b/graphics/fonts/ttf.cpp
@@ -109,6 +109,8 @@ public:
 
 	virtual int getCharWidth(byte chr) const;
 
+	virtual int getKerningOffset(byte left, byte right) const;
+
 	virtual void drawChar(Surface *dst, byte chr, int x, int y, uint32 color) const;
 private:
 	bool _initialized;
@@ -126,16 +128,19 @@ private:
 		int advance;
 	};
 
-	bool cacheGlyph(Glyph &glyph, byte chr);
+	bool cacheGlyph(Glyph &glyph, FT_UInt &slot, uint chr);
 	typedef Common::HashMap<byte, Glyph> GlyphCache;
 	GlyphCache _glyphs;
 
+	FT_UInt _glyphSlots[256];
+
 	bool _monochrome;
+	bool _hasKerning;
 };
 
 TTFFont::TTFFont()
     : _initialized(false), _face(), _ttfFile(0), _size(0), _width(0), _height(0), _ascent(0),
-      _descent(0), _glyphs(), _monochrome(false) {
+      _descent(0), _glyphs(), _glyphSlots(), _monochrome(false), _hasKerning(false) {
 }
 
 TTFFont::~TTFFont() {
@@ -187,6 +192,9 @@ bool TTFFont::load(Common::SeekableReadStream &stream, int size, bool monochrome
 		return false;
 	}
 
+	// Check whether we have kerning support
+	_hasKerning = (FT_HAS_KERNING(_face) != 0);
+
 	if (FT_Set_Char_Size(_face, 0, size * 64, 0, 0)) {
 		delete[] _ttfFile;
 		_ttfFile = 0;
@@ -204,8 +212,10 @@ bool TTFFont::load(Common::SeekableReadStream &stream, int size, bool monochrome
 	_height = _ascent - _descent + 1;
 
 	// Load all ISO-8859-1 characters.
-	for (uint i = 0; i < 256; ++i)
-		cacheGlyph(_glyphs[i], i);
+	for (uint i = 0; i < 256; ++i) {
+		if (!cacheGlyph(_glyphs[i], _glyphSlots[i], i))
+			_glyphSlots[i] = 0;
+	}
 
 	_initialized = (_glyphs.size() != 0);
 	return _initialized;
@@ -227,6 +237,21 @@ int TTFFont::getCharWidth(byte chr) const {
 		return glyphEntry->_value.advance;
 }
 
+int TTFFont::getKerningOffset(byte left, byte right) const {
+	if (!_hasKerning)
+		return 0;
+
+	FT_UInt leftGlyph = _glyphSlots[left];
+	FT_UInt rightGlyph = _glyphSlots[right];
+
+	if (!leftGlyph || !rightGlyph)
+		return 0;
+
+	FT_Vector kerningVector;
+	FT_Get_Kerning(_face, leftGlyph, rightGlyph, FT_KERNING_DEFAULT, &kerningVector);
+	return (kerningVector.x / 64);
+}
+
 namespace {
 
 template<typename ColorType>
@@ -336,8 +361,8 @@ void TTFFont::drawChar(Surface *dst, byte chr, int x, int y, uint32 color) const
 	}
 }
 
-bool TTFFont::cacheGlyph(Glyph &glyph, byte chr) {
-	FT_UInt slot = FT_Get_Char_Index(_face, chr);
+bool TTFFont::cacheGlyph(Glyph &glyph, FT_UInt &slot, uint chr) {
+	slot = FT_Get_Char_Index(_face, chr);
 	if (!slot)
 		return false;