Initial (WIP) Harfbuzz text shaping integration.

This a significant refactor / rewrite of much of the love.graphics Font code.
Text positioning is now split into TextShaper classes in the love.font module. This isn't exposed to users yet.
BMFonts and ImageFonts use the same text shaping as before (in the new TextShaper API). Fonts loaded via FreeType now use Harfbuzz for text shaping.

The new code isn't at feature-parity with the old code yet. Harfbuzz-based text shaping enables kerning support in more fonts, character combining into ligature glyphs, and directions other than left-to-right (this isn't supported in love yet).

src/modules/font/BMFontRasterizer.cpp

@@ -20,6 +20,7 @@
 
 // LOVE
 #include "BMFontRasterizer.h"
+#include "GenericShaper.h"
 #include "filesystem/Filesystem.h"
 #include "image/Image.h"
 
@@ -164,6 +165,14 @@ BMFontRasterizer::~BMFontRasterizer()
 
 void BMFontRasterizer::parseConfig(const std::string &configtext)
 {
+	{
+		BMFontCharacter nullchar = {};
+		nullchar.page = -1;
+		nullchar.glyph = 0;
+		characters.push_back(nullchar);
+		characterIndices[0] = (int)characters.size() - 1;
+	}
+
 	std::stringstream ss(configtext);
 	std::string line;
 
@@ -237,7 +246,10 @@ void BMFontRasterizer::parseConfig(const std::string &configtext)
 			c.metrics.bearingY = -cline.getAttributeInt("yoffset");
 			c.metrics.advance  =  cline.getAttributeInt("xadvance");
 
-			characters[id] = c;
+			c.glyph = id;
+
+			characters.push_back(c);
+			characterIndices[id] = (int) characters.size() - 1;
 		}
 		else if (tag == "kerning")
 		{
@@ -257,13 +269,15 @@ void BMFontRasterizer::parseConfig(const std::string &configtext)
 	bool guessheight = lineHeight == 0;
 
 	// Verify the glyph character attributes.
-	for (const auto &cpair : characters)
+	for (const auto &c : characters)
 	{
-		const BMFontCharacter &c = cpair.second;
+		if (c.glyph == 0)
+			continue;
+
 		int width = c.metrics.width;
 		int height = c.metrics.height;
 
-		if (!unicode && cpair.first > 127)
+		if (!unicode && c.glyph > 127)
 			throw love::Exception("Invalid BMFont character id (only unicode and ASCII are supported)");
 
 		if (c.page < 0 || images[c.page].get() == nullptr)
@@ -272,13 +286,13 @@ void BMFontRasterizer::parseConfig(const std::string &configtext)
 		const image::ImageData *id = images[c.page].get();
 
 		if (!id->inside(c.x, c.y))
-			throw love::Exception("Invalid coordinates for BMFont character %u.", cpair.first);
+			throw love::Exception("Invalid coordinates for BMFont character %u.", c.glyph);
 
 		if (width > 0 && !id->inside(c.x + width - 1, c.y))
-			throw love::Exception("Invalid width %d for BMFont character %u.", width, cpair.first);
+			throw love::Exception("Invalid width %d for BMFont character %u.", width, c.glyph);
 
 		if (height > 0 && !id->inside(c.x, c.y + height - 1))
-			throw love::Exception("Invalid height %d for BMFont character %u.", height, cpair.first);
+			throw love::Exception("Invalid height %d for BMFont character %u.", height, c.glyph);
 
 		if (guessheight)
 			lineHeight = std::max(lineHeight, c.metrics.height);
@@ -292,22 +306,37 @@ int BMFontRasterizer::getLineHeight() const
 	return lineHeight;
 }
 
-GlyphData *BMFontRasterizer::getGlyphData(uint32 glyph) const
+int BMFontRasterizer::getGlyphSpacing(uint32 glyph) const
 {
-	auto it = characters.find(glyph);
+	auto it = characterIndices.find(glyph);
+	if (it == characterIndices.end())
+		return 0;
 
+	return characters[it->second].metrics.advance;
+}
+
+int BMFontRasterizer::getGlyphIndex(uint32 glyph) const
+{
+	auto it = characterIndices.find(glyph);
+	if (it == characterIndices.end())
+		return 0;
+	return it->second;
+}
+
+GlyphData *BMFontRasterizer::getGlyphDataForIndex(int index) const
+{
 	// Return an empty GlyphData if we don't have the glyph character.
-	if (it == characters.end())
-		return new GlyphData(glyph, GlyphMetrics(), PIXELFORMAT_RGBA8_UNORM);
+	if (index < 0 || index >= (int) characters.size())
+		return new GlyphData(0, GlyphMetrics(), PIXELFORMAT_RGBA8_UNORM);
 
-	const BMFontCharacter &c = it->second;
+	const BMFontCharacter& c = characters[index];
 	const auto &imagepair = images.find(c.page);
 
 	if (imagepair == images.end())
-		return new GlyphData(glyph, GlyphMetrics(), PIXELFORMAT_RGBA8_UNORM);
+		return new GlyphData(c.glyph, GlyphMetrics(), PIXELFORMAT_RGBA8_UNORM);
 
 	image::ImageData *imagedata = imagepair->second.get();
-	GlyphData *g = new GlyphData(glyph, c.metrics, PIXELFORMAT_RGBA8_UNORM);
+	GlyphData *g = new GlyphData(c.glyph, c.metrics, PIXELFORMAT_RGBA8_UNORM);
 
 	size_t pixelsize = imagedata->getPixelSize();
 
@@ -333,7 +362,7 @@ int BMFontRasterizer::getGlyphCount() const
 
 bool BMFontRasterizer::hasGlyph(uint32 glyph) const
 {
-	return characters.find(glyph) != characters.end();
+	return characterIndices.find(glyph) != characterIndices.end();
 }
 
 float BMFontRasterizer::getKerning(uint32 leftglyph, uint32 rightglyph) const
@@ -352,6 +381,11 @@ Rasterizer::DataType BMFontRasterizer::getDataType() const
 	return DATA_IMAGE;
 }
 
+TextShaper *BMFontRasterizer::newTextShaper()
+{
+	return new GenericShaper(this);
+}
+
 bool BMFontRasterizer::accepts(love::filesystem::FileData *fontdef)
 {
 	const char *data = (const char *) fontdef->getData();