Support for loading a certain font face from a font file.

This commit allows loading a certain font face from a font collection file such as TTC.

src/fontstash.h

@@ -102,8 +102,8 @@ int fonsExpandAtlas(FONScontext* s, int width, int height);
 int fonsResetAtlas(FONScontext* stash, int width, int height);
 
 // Add fonts
-int fonsAddFont(FONScontext* s, const char* name, const char* path);
-int fonsAddFontMem(FONScontext* s, const char* name, unsigned char* data, int ndata, int freeData);
+int fonsAddFont(FONScontext* s, const char* name, const char* path, int fontIndex);
+int fonsAddFontMem(FONScontext* s, const char* name, unsigned char* data, int ndata, int freeData, int fontIndex);
 int fonsGetFontByName(FONScontext* s, const char* name);
 
 // State handling
@@ -175,13 +175,13 @@ int fons__tt_done(FONScontext *context)
 	return ftError == 0;
 }
 
-int fons__tt_loadFont(FONScontext *context, FONSttFontImpl *font, unsigned char *data, int dataSize)
+int fons__tt_loadFont(FONScontext *context, FONSttFontImpl *font, unsigned char *data, int dataSize, int fontIndex)
 {
 	FT_Error ftError;
 	FONS_NOTUSED(context);
 
 	//font->font.userdata = stash;
-	ftError = FT_New_Memory_Face(ftLibrary, (const FT_Byte*)data, dataSize, 0, &font->font);
+	ftError = FT_New_Memory_Face(ftLibrary, (const FT_Byte*)data, dataSize, fontIndex, &font->font);
 	return ftError == 0;
 }
 
@@ -278,13 +278,18 @@ int fons__tt_done(FONScontext *context)
 	return 1;
 }
 
-int fons__tt_loadFont(FONScontext *context, FONSttFontImpl *font, unsigned char *data, int dataSize)
+int fons__tt_loadFont(FONScontext *context, FONSttFontImpl *font, unsigned char *data, int dataSize, int fontIndex)
 {
-	int stbError;
+	int offset, stbError;
 	FONS_NOTUSED(dataSize);
 
 	font->font.userdata = context;
-	stbError = stbtt_InitFont(&font->font, data, 0);
+	offset = stbtt_GetFontOffsetForIndex(data, fontIndex);
+	if (offset == -1) {
+		stbError = 0;
+	} else {
+		stbError = stbtt_InitFont(&font->font, data, offset);
+	}
 	return stbError;
 }
 
@@ -890,7 +895,7 @@ error:
 	return FONS_INVALID;
 }
 
-int fonsAddFont(FONScontext* stash, const char* name, const char* path)
+int fonsAddFont(FONScontext* stash, const char* name, const char* path, int fontIndex)
 {
 	FILE* fp = 0;
 	int dataSize = 0;
@@ -910,7 +915,7 @@ int fonsAddFont(FONScontext* stash, const char* name, const char* path)
 	fp = 0;
 	if (readed != dataSize) goto error;
 
-	return fonsAddFontMem(stash, name, data, dataSize, 1);
+	return fonsAddFontMem(stash, name, data, dataSize, 1, fontIndex);
 
 error:
 	if (data) free(data);
@@ -918,7 +923,7 @@ error:
 	return FONS_INVALID;
 }
 
-int fonsAddFontMem(FONScontext* stash, const char* name, unsigned char* data, int dataSize, int freeData)
+int fonsAddFontMem(FONScontext* stash, const char* name, unsigned char* data, int dataSize, int freeData, int fontIndex)
 {
 	int i, ascent, descent, fh, lineGap;
 	FONSfont* font;
@@ -943,7 +948,7 @@ int fonsAddFontMem(FONScontext* stash, const char* name, unsigned char* data, in
 
 	// Init font
 	stash->nscratch = 0;
-	if (!fons__tt_loadFont(stash, &font->font, data, dataSize)) goto error;
+	if (!fons__tt_loadFont(stash, &font->font, data, dataSize, fontIndex)) goto error;
 
 	// Store normalized line height. The real line height is got
 	// by multiplying the lineh by font size.

src/nanovg.c

@@ -2287,14 +2287,24 @@ void nvgStroke(NVGcontext* ctx)
 }
 
 // Add fonts
-int nvgCreateFont(NVGcontext* ctx, const char* name, const char* path)
+int nvgCreateFont(NVGcontext* ctx, const char* name, const char* filename)
 {
-	return fonsAddFont(ctx->fs, name, path);
+	return fonsAddFont(ctx->fs, name, filename, 0);
+}
+
+int nvgCreateFontAtIndex(NVGcontext* ctx, const char* name, const char* filename, const int fontIndex)
+{
+	return fonsAddFont(ctx->fs, name, filename, fontIndex);
 }
 
 int nvgCreateFontMem(NVGcontext* ctx, const char* name, unsigned char* data, int ndata, int freeData)
 {
-	return fonsAddFontMem(ctx->fs, name, data, ndata, freeData);
+	return fonsAddFontMem(ctx->fs, name, data, ndata, freeData, 0);
+}
+
+int nvgCreateFontMemAtIndex(NVGcontext* ctx, const char* name, unsigned char* data, int ndata, int freeData, const int fontIndex)
+{
+	return fonsAddFontMem(ctx->fs, name, data, ndata, freeData, fontIndex);
 }
 
 int nvgFindFont(NVGcontext* ctx, const char* name)

src/nanovg.h

@@ -546,10 +546,16 @@ void nvgStroke(NVGcontext* ctx);
 // Returns handle to the font.
 int nvgCreateFont(NVGcontext* ctx, const char* name, const char* filename);
 
+// fontIndex specifies which font face to load from a .ttf/.ttc file.
+int nvgCreateFontAtIndex(NVGcontext* ctx, const char* name, const char* filename, const int fontIndex);
+
 // Creates font by loading it from the specified memory chunk.
 // Returns handle to the font.
 int nvgCreateFontMem(NVGcontext* ctx, const char* name, unsigned char* data, int ndata, int freeData);
 
+// fontIndex specifies which font face to load from a .ttf/.ttc file.
+int nvgCreateFontMemAtIndex(NVGcontext* ctx, const char* name, unsigned char* data, int ndata, int freeData, const int fontIndex);
+
 // Finds a loaded font of specified name, and returns handle to it, or -1 if the font is not found.
 int nvgFindFont(NVGcontext* ctx, const char* name);