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Fixed bug 4307 - Improve SDL_ttf glyph cache system
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Sylvain

Using Index instead of Glyph is a better option to ease the integration of a text shaping engine into SDL_ttf (like in bug 3046 and bug 3211). It also doesn't break current SDL_ttf.

This way, SDL_ttf can have in the future a function to render an array of indexes e.g:

    SDL_Surface *TTF_RenderINDEX_Solid(TTF_Font *font, int *indexes, int nb_indexes, SDL_Color fg);

Where (indexes, nb_indexes) would be produced by a text shaping engine.

Having a text shaping engine is essential to render text correctly. To be picky, even English language needs it to render ligatures like "fi".
https://en.wikipedia.org/wiki/Typographic_ligature
https://en.wikipedia.org/wiki/Typographic_ligature#/media/File:Ligatures.svg
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@slouken
slouken committed Nov 6, 2018
1 parent af95c8a commit 5de806d
Showing 1 changed file with 26 additions and 22 deletions.
48 changes: 26 additions & 22 deletions SDL_ttf.c
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Expand Up @@ -60,7 +60,7 @@ typedef struct cached_glyph {
int maxy;
int yoffset;
int advance;
Uint32 cached;
SDL_bool is_cached;
} c_glyph;

/* The structure used to hold internal font information */
Expand Down Expand Up @@ -134,7 +134,7 @@ static int TTF_byteswapped = 0;
}


static int TTF_initFontMetrics(TTF_Font* font);
static int TTF_initFontMetrics(TTF_Font *font);

/* Draw a solid or shaded line of underline_height at the given row. */
static void TTF_drawLine(const TTF_Font *font, const SDL_Surface *textbuf, int row, int color)
Expand Down Expand Up @@ -251,7 +251,7 @@ static unsigned long RWread(

TTF_Font* TTF_OpenFontIndexRW(SDL_RWops *src, int freesrc, int ptsize, long index)
{
TTF_Font* font;
TTF_Font *font;
FT_Error error;
FT_Face face;
FT_Stream stream;
Expand Down Expand Up @@ -407,7 +407,7 @@ TTF_Font* TTF_OpenFontIndexRW(SDL_RWops *src, int freesrc, int ptsize, long inde
}

/* Update font parameter depending on a style change */
static int TTF_initFontMetrics(TTF_Font* font)
static int TTF_initFontMetrics(TTF_Font *font)
{
FT_Face face = font->face;

Expand All @@ -429,7 +429,7 @@ static int TTF_initFontMetrics(TTF_Font* font)
font->descent = FT_CEIL(face->size->metrics.descender);
font->height = FT_CEIL(face->size->metrics.height);
font->lineskip = FT_CEIL(face->size->metrics.height);
/* face->underline_position and face->underline_height are only
/* face->underline_position and face->underline_height are only
* relevant for scalable formats (see freetype.h FT_FaceRec)*/
font->underline_offset = font->descent / 2;
font->underline_height = 1;
Expand Down Expand Up @@ -500,7 +500,7 @@ TTF_Font* TTF_OpenFont(const char *file, int ptsize)
return TTF_OpenFontIndex(file, ptsize, 0);
}

static void Flush_Glyph(c_glyph* glyph)
static void Flush_Glyph(c_glyph *glyph)
{
glyph->stored = 0;
glyph->index = 0;
Expand All @@ -512,28 +512,28 @@ static void Flush_Glyph(c_glyph* glyph)
SDL_free(glyph->pixmap.buffer);
glyph->pixmap.buffer = 0;
}
glyph->cached = 0;
glyph->is_cached = SDL_FALSE;
}

static void Flush_Cache(TTF_Font* font)
static void Flush_Cache(TTF_Font *font)
{
int i;
int size = sizeof(font->cache) / sizeof(font->cache[0]);

for (i = 0; i < size; ++i) {
if (font->cache[i].cached) {
if (font->cache[i].is_cached) {
Flush_Glyph(&font->cache[i]);
}
}
}

static FT_Error Load_Glyph(TTF_Font* font, Uint32 ch, c_glyph* cached, int want)
static FT_Error Load_Glyph(TTF_Font *font, Uint32 idx, c_glyph *cached, int want)
{
FT_Face face;
FT_Error error;
FT_GlyphSlot glyph;
FT_Glyph_Metrics* metrics;
FT_Outline* outline;
FT_Glyph_Metrics *metrics;
FT_Outline *outline;

if (!font || !font->face) {
return FT_Err_Invalid_Handle;
Expand All @@ -542,9 +542,8 @@ static FT_Error Load_Glyph(TTF_Font* font, Uint32 ch, c_glyph* cached, int want)
face = font->face;

/* Load the glyph */
if (!cached->index) {
cached->index = FT_Get_Char_Index(face, ch);
}
cached->index = idx;

error = FT_Load_Glyph(face, cached->index, FT_LOAD_DEFAULT | font->hinting);
if (error) {
return error;
Expand Down Expand Up @@ -591,8 +590,8 @@ static FT_Error Load_Glyph(TTF_Font* font, Uint32 ch, c_glyph* cached, int want)
((want & CACHED_PIXMAP) && !(cached->stored & CACHED_PIXMAP))) {
int mono = (want & CACHED_BITMAP);
unsigned int i;
FT_Bitmap* src;
FT_Bitmap* dst;
FT_Bitmap *src;
FT_Bitmap *dst;
FT_Glyph bitmap_glyph = NULL;

/* Handle the italic style, only for scalable fonts */
Expand Down Expand Up @@ -833,29 +832,34 @@ static FT_Error Load_Glyph(TTF_Font* font, Uint32 ch, c_glyph* cached, int want)
}

/* We're done, mark this glyph cached */
cached->cached = ch;
cached->is_cached = SDL_TRUE;

return 0;
}

static FT_Error Find_Glyph(TTF_Font *font, Uint32 ch, int want)
static FT_Error Find_GlyphByIndex(TTF_Font *font, FT_UInt idx, int want)
{
int retval = 0;
int hsize = sizeof(font->cache) / sizeof(font->cache[0]);

int h = ch % hsize;
int h = idx % hsize;
font->current = &font->cache[h];

if (font->current->cached != ch) {
if (font->current->is_cached && font->current->index != idx) {
Flush_Glyph(font->current);
}

if ((font->current->stored & want) != want) {
retval = Load_Glyph(font, ch, font->current, want);
retval = Load_Glyph(font, idx, font->current, want);
}
return retval;
}

static FT_Error Find_Glyph(TTF_Font *font, Uint32 ch, int want) {
Uint32 idx = FT_Get_Char_Index(font->face, ch);
return Find_GlyphByIndex(font, idx, want);
}

void TTF_CloseFont(TTF_Font *font)
{
if (font) {
Expand Down

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