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add SDF support when using stb_truetype backend
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@wheybags
wheybags committed Dec 16, 2017
1 parent 539d871 commit edab822
Showing 1 changed file with 80 additions and 8 deletions.
88 changes: 80 additions & 8 deletions src/fontstash.h
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,21 @@ struct FONStextIter {
};
typedef struct FONStextIter FONStextIter;

// See also: stb_truetype documentation for stbtt_GetGlyphSDF. These parameters are copied from there
struct FONSsdfSettings
{
unsigned char sdfEnabled;
unsigned char onedgeValue; // value 0-255 to test the SDF against to reconstruct the character (i.e. the isocontour of the character)

int padding; // extra "pixels" around the character which are filled with the distance to the character (not 0),
// which allows effects like bit outlines

float pixelDistScale; // what value the SDF should increase by when moving one SDF "pixel" away from the edge (on the 0..255 scale)
// if positive, > onedge_value is inside; if negative, < onedge_value is inside
};
typedef struct FONSsdfSettings FONSsdfSettings;


typedef struct FONScontext FONScontext;

// Contructor and destructor.
Expand All @@ -109,6 +124,12 @@ FONS_DEF int fonsResetAtlas(FONScontext* stash, int width, int height);
// Add fonts
FONS_DEF int fonsAddFont(FONScontext* s, const char* name, const char* path);
FONS_DEF int fonsAddFontMem(FONScontext* s, const char* name, unsigned char* data, int ndata, int freeData);

#ifndef FONS_USE_FREETYPE
FONS_DEF int fonsAddFontSdf(FONScontext* s, const char* name, const char* path, FONSsdfSettings sdfSettings);
FONS_DEF int fonsAddFontSdfMem(FONScontext* s, const char* name, unsigned char* data, int ndata, int freeData, FONSsdfSettings sdfSettings);
#endif

FONS_DEF int fonsGetFontByName(FONScontext* s, const char* name);

// State handling
Expand Down Expand Up @@ -204,12 +225,13 @@ static int fons__tt_getGlyphIndex(FONSttFontImpl *font, int codepoint)
}

static int fons__tt_buildGlyphBitmap(FONSttFontImpl *font, int glyph, float size, float scale,
int *advance, int *lsb, int *x0, int *y0, int *x1, int *y1)
int *advance, int *lsb, int *x0, int *y0, int *x1, int *y1, const FONSsdfSettings* sdfSettings)
{
FT_Error ftError;
FT_GlyphSlot ftGlyph;
FT_Fixed advFixed;
FONS_NOTUSED(scale);
FONS_NOTUSED(sdfSettings);

ftError = FT_Set_Pixel_Sizes(font->font, 0, (FT_UInt)(size * (float)font->font->units_per_EM / (float)(font->font->ascender - font->font->descender)));
if (ftError) return 0;
Expand All @@ -228,7 +250,7 @@ static int fons__tt_buildGlyphBitmap(FONSttFontImpl *font, int glyph, float size
}

static void fons__tt_renderGlyphBitmap(FONSttFontImpl *font, unsigned char *output, int outWidth, int outHeight, int outStride,
float scaleX, float scaleY, int glyph)
float scaleX, float scaleY, int glyph, const FONSsdfSettings* sdfSettings)
{
FT_GlyphSlot ftGlyph = font->font->glyph;
int ftGlyphOffset = 0;
Expand All @@ -238,6 +260,7 @@ static void fons__tt_renderGlyphBitmap(FONSttFontImpl *font, unsigned char *outp
FONS_NOTUSED(scaleX);
FONS_NOTUSED(scaleY);
FONS_NOTUSED(glyph); // glyph has already been loaded by fons__tt_buildGlyphBitmap
FONS_NOTUSED(sdfSettings);

for ( y = 0; y < ftGlyph->bitmap.rows; y++ ) {
for ( x = 0; x < ftGlyph->bitmap.width; x++ ) {
Expand Down Expand Up @@ -300,18 +323,46 @@ static int fons__tt_getGlyphIndex(FONSttFontImpl *font, int codepoint)
}

static int fons__tt_buildGlyphBitmap(FONSttFontImpl *font, int glyph, float size, float scale,
int *advance, int *lsb, int *x0, int *y0, int *x1, int *y1)
int *advance, int *lsb, int *x0, int *y0, int *x1, int *y1, const FONSsdfSettings* sdfSettings)
{
FONS_NOTUSED(size);
stbtt_GetGlyphHMetrics(&font->font, glyph, advance, lsb);
stbtt_GetGlyphBitmapBox(&font->font, glyph, scale, scale, x0, y0, x1, y1);

if (sdfSettings->sdfEnabled)
{
*x0 -= sdfSettings->padding;
*y0 -= sdfSettings->padding;
*x1 += sdfSettings->padding;
*y1 += sdfSettings->padding;
}

return 1;
}

static void fons__tt_renderGlyphBitmap(FONSttFontImpl *font, unsigned char *output, int outWidth, int outHeight, int outStride,
float scaleX, float scaleY, int glyph)
float scaleX, float scaleY, int glyph, const FONSsdfSettings* sdfSettings)
{
stbtt_MakeGlyphBitmap(&font->font, output, outWidth, outHeight, outStride, scaleX, scaleY, glyph);
if (!sdfSettings->sdfEnabled)
{
stbtt_MakeGlyphBitmap(&font->font, output, outWidth, outHeight, outStride, scaleX, scaleY, glyph);
}
else
{
int w = 0, h = 0, xoff = 0, yoff = 0;
unsigned char* sdfData = stbtt_GetGlyphSDF(&font->font, scaleX, glyph, sdfSettings->padding, sdfSettings->onedgeValue, sdfSettings->pixelDistScale, &w, &h, &xoff, &yoff);

for (int y = 0; y < h; y++)
{
unsigned char* outRow = output + (outStride*y);
unsigned char* inRow = sdfData + (w*y);

memcpy(outRow, inRow, w);
}

if (sdfData)
stbtt_FreeSDF(sdfData, NULL);
}
}

static int fons__tt_getGlyphKernAdvance(FONSttFontImpl *font, int glyph1, int glyph2)
Expand Down Expand Up @@ -394,6 +445,7 @@ struct FONSfont
int lut[FONS_HASH_LUT_SIZE];
int fallbacks[FONS_MAX_FALLBACKS];
int nfallbacks;
FONSsdfSettings sdfSettings;
};
typedef struct FONSfont FONSfont;

Expand Down Expand Up @@ -916,6 +968,15 @@ static FILE* fons__fopen(const char* filename, const char* mode)
}

int fonsAddFont(FONScontext* stash, const char* name, const char* path)
{
FONSsdfSettings sdfSettings;
memset(&sdfSettings, 0, sizeof(FONSsdfSettings));
sdfSettings.sdfEnabled = 0;

return fonsAddFontSdf(stash, name, path, sdfSettings);
}

int fonsAddFontSdf(FONScontext* stash, const char* name, const char* path, FONSsdfSettings sdfSettings)
{
FILE* fp = 0;
int dataSize = 0, readed;
Expand All @@ -934,7 +995,7 @@ 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 fonsAddFontSdfMem(stash, name, data, dataSize, 1, sdfSettings);

error:
if (data) free(data);
Expand All @@ -943,6 +1004,16 @@ int fonsAddFont(FONScontext* stash, const char* name, const char* path)
}

int fonsAddFontMem(FONScontext* stash, const char* name, unsigned char* data, int dataSize, int freeData)
{
FONSsdfSettings sdfSettings;
memset(&sdfSettings, 0, sizeof(FONSsdfSettings));
sdfSettings.sdfEnabled = 0;

return fonsAddFontSdfMem(stash, name, data, dataSize, freeData, sdfSettings);
}


int fonsAddFontSdfMem(FONScontext* stash, const char* name, unsigned char* data, int dataSize, int freeData, FONSsdfSettings sdfSettings)
{
int i, ascent, descent, fh, lineGap;
FONSfont* font;
Expand All @@ -952,6 +1023,7 @@ int fonsAddFontMem(FONScontext* stash, const char* name, unsigned char* data, in
return FONS_INVALID;

font = stash->fonts[idx];
font->sdfSettings = sdfSettings;

strncpy(font->name, name, sizeof(font->name));
font->name[sizeof(font->name)-1] = '\0';
Expand Down Expand Up @@ -1119,7 +1191,7 @@ static FONSglyph* fons__getGlyph(FONScontext* stash, FONSfont* font, unsigned in
// In that case the glyph index 'g' is 0, and we'll proceed below and cache empty glyph.
}
scale = fons__tt_getPixelHeightScale(&renderFont->font, size);
fons__tt_buildGlyphBitmap(&renderFont->font, g, size, scale, &advance, &lsb, &x0, &y0, &x1, &y1);
fons__tt_buildGlyphBitmap(&renderFont->font, g, size, scale, &advance, &lsb, &x0, &y0, &x1, &y1, &renderFont->sdfSettings);
gw = x1-x0 + pad*2;
gh = y1-y0 + pad*2;

Expand Down Expand Up @@ -1153,7 +1225,7 @@ static FONSglyph* fons__getGlyph(FONScontext* stash, FONSfont* font, unsigned in

// Rasterize
dst = &stash->texData[(glyph->x0+pad) + (glyph->y0+pad) * stash->params.width];
fons__tt_renderGlyphBitmap(&renderFont->font, dst, gw-pad*2,gh-pad*2, stash->params.width, scale,scale, g);
fons__tt_renderGlyphBitmap(&renderFont->font, dst, gw-pad*2,gh-pad*2, stash->params.width, scale,scale, g, &renderFont->sdfSettings);

// Make sure there is one pixel empty border.
dst = &stash->texData[glyph->x0 + glyph->y0 * stash->params.width];
Expand Down

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