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374 lines (325 loc) · 12.6 KB
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//-----------------------------------------------------------------------------
// Routines to read a TrueType font as vector outlines, and generate them
// as entities, since they're always representable as either lines or
// quadratic Bezier curves.
//
// Copyright 2016 whitequark, Peter Barfuss.
//-----------------------------------------------------------------------------
#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_OUTLINE_H
#include FT_ADVANCES_H
/* Yecch. Irritatingly, you need to do this nonsense to get the error string table,
since nobody thought to put this exact function into FreeType itsself. */
#undef __FTERRORS_H__
#define FT_ERRORDEF(e, v, s) { (e), (s) },
#define FT_ERROR_START_LIST
#define FT_ERROR_END_LIST { 0, NULL }
struct ft_error {
int err;
const char *str;
};
static const struct ft_error ft_errors[] = {
#include FT_ERRORS_H
};
extern "C" const char *ft_error_string(int err) {
const struct ft_error *e;
for(e = ft_errors; e->str; e++)
if(e->err == err)
return e->str;
return "Unknown error";
}
/* Okay, we're done with that. */
#undef FT_ERRORDEF
#undef FT_ERROR_START_LIST
#undef FT_ERROR_END_LIST
#include "solvespace.h"
//-----------------------------------------------------------------------------
// Get the list of available font filenames, and load the name for each of
// them. Only that, though, not the glyphs too.
//-----------------------------------------------------------------------------
TtfFontList::TtfFontList() {
FT_Init_FreeType(&fontLibrary);
}
TtfFontList::~TtfFontList() {
FT_Done_FreeType(fontLibrary);
}
void TtfFontList::LoadAll() {
if(loaded) return;
for(const std::string &font : GetFontFiles()) {
TtfFont tf = {};
tf.fontFile = font;
if(tf.LoadFromFile(fontLibrary))
l.Add(&tf);
}
// Sort fonts according to their actual name, not filename.
std::sort(&l.elem[0], &l.elem[l.n],
[](const TtfFont &a, const TtfFont &b) { return a.name < b.name; });
// Filter out fonts with the same family and style name. This is not
// strictly necessarily the exact same font, but it will almost always be.
TtfFont *it = std::unique(&l.elem[0], &l.elem[l.n],
[](const TtfFont &a, const TtfFont &b) { return a.name == b.name; });
l.RemoveLast(&l.elem[l.n] - it);
// TODO: identify fonts by their name and not filename, which may change
// between OSes.
loaded = true;
}
TtfFont *TtfFontList::LoadFont(const std::string &font)
{
LoadAll();
TtfFont *tf = std::find_if(l.begin(), l.end(),
[&](const TtfFont &tf) { return tf.FontFileBaseName() == font; });
if(tf != l.end()) {
if(tf->fontFace == NULL) {
tf->LoadFromFile(fontLibrary, /*nameOnly=*/false);
}
return tf;
} else {
return NULL;
}
}
void TtfFontList::PlotString(const std::string &font, const std::string &str,
SBezierList *sbl, Vector origin, Vector u, Vector v)
{
TtfFont *tf = LoadFont(font);
if(!str.empty() && tf != NULL) {
tf->PlotString(str, sbl, origin, u, v);
} else {
// No text or no font; so draw a big X for an error marker.
SBezier sb;
sb = SBezier::From(origin, origin.Plus(u).Plus(v));
sbl->l.Add(&sb);
sb = SBezier::From(origin.Plus(v), origin.Plus(u));
sbl->l.Add(&sb);
}
}
double TtfFontList::AspectRatio(const std::string &font, const std::string &str)
{
TtfFont *tf = LoadFont(font);
if(tf != NULL) {
return tf->AspectRatio(str);
}
return 0.0;
}
//-----------------------------------------------------------------------------
// Return the basename of our font filename; that's how the requests and
// entities that reference us will store it.
//-----------------------------------------------------------------------------
std::string TtfFont::FontFileBaseName() const {
std::string baseName = fontFile;
size_t pos = baseName.rfind(PATH_SEP);
if(pos != std::string::npos)
return baseName.erase(0, pos + 1);
return "";
}
//-----------------------------------------------------------------------------
// Load a TrueType font into memory. We care about the curves that define
// the letter shapes, and about the mappings that determine which glyph goes
// with which character.
//-----------------------------------------------------------------------------
bool TtfFont::LoadFromFile(FT_Library fontLibrary, bool nameOnly) {
FT_Open_Args args = {};
args.flags = FT_OPEN_PATHNAME;
args.pathname = &fontFile[0]; // FT_String is char* for historical reasons
// We don't use ssfopen() here to let freetype do its own memory management.
// This is OK because on Linux/OS X we just delegate to fopen and on Windows
// we only look into C:\Windows\Fonts, which has a known short path.
if(int fterr = FT_Open_Face(fontLibrary, &args, 0, &fontFace)) {
dbp("freetype: loading font from file '%s' failed: %s",
fontFile.c_str(), ft_error_string(fterr));
return false;
}
if(int fterr = FT_Select_Charmap(fontFace, FT_ENCODING_UNICODE)) {
dbp("freetype: loading unicode CMap for file '%s' failed: %s",
fontFile.c_str(), ft_error_string(fterr));
FT_Done_Face(fontFace);
fontFace = NULL;
return false;
}
name = std::string(fontFace->family_name) +
" (" + std::string(fontFace->style_name) + ")";
if(nameOnly) {
FT_Done_Face(fontFace);
fontFace = NULL;
return true;
}
// We always ask Freetype to give us a unit size character.
// It uses fixed point; put the unit size somewhere in the middle of the dynamic
// range of its 26.6 fixed point type, and adjust the factors so that the unit
// matches cap height.
FT_Size_RequestRec sizeRequest;
sizeRequest.type = FT_SIZE_REQUEST_TYPE_REAL_DIM;
sizeRequest.width = 1 << 16;
sizeRequest.height = 1 << 16;
sizeRequest.horiResolution = 128;
sizeRequest.vertResolution = 128;
if(int fterr = FT_Request_Size(fontFace, &sizeRequest)) {
dbp("freetype: cannot set character size: %s",
ft_error_string(fterr));
FT_Done_Face(fontFace);
fontFace = NULL;
return false;
}
char chr = 'A';
uint32_t gid = FT_Get_Char_Index(fontFace, 'A');
if (gid == 0) {
dbp("freetype: CID-to-GID mapping for CID 0x%04x failed: %s; using CID as GID",
chr, ft_error_string(gid));
gid = chr;
}
if(gid) {
if(int fterr = FT_Load_Glyph(fontFace, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING)) {
dbp("freetype: cannot load glyph for GID 0x%04x: %s",
gid, ft_error_string(fterr));
FT_Done_Face(fontFace);
fontFace = NULL;
return false;
}
FT_BBox bbox;
FT_Outline_Get_CBox(&fontFace->glyph->outline, &bbox);
capHeight = (double)bbox.yMax;
}
return true;
}
typedef struct OutlineData {
Vector origin, u, v; // input parameters
SBezierList *beziers; // output bezier list
float factor; // ratio between freetype and solvespace coordinates
FT_Pos bx; // x offset of the current glyph
FT_Pos px, py; // current point
} OutlineData;
static Vector Transform(OutlineData *data, FT_Pos x, FT_Pos y) {
Vector r = data->origin;
r = r.Plus(data->u.ScaledBy((float)(data->bx + x) * data->factor));
r = r.Plus(data->v.ScaledBy((float)y * data->factor));
return r;
}
static int MoveTo(const FT_Vector *p, void *cc)
{
OutlineData *data = (OutlineData *) cc;
data->px = p->x;
data->py = p->y;
return 0;
}
static int LineTo(const FT_Vector *p, void *cc)
{
OutlineData *data = (OutlineData *) cc;
SBezier sb = SBezier::From(
Transform(data, data->px, data->py),
Transform(data, p->x, p->y));
data->beziers->l.Add(&sb);
data->px = p->x;
data->py = p->y;
return 0;
}
static int ConicTo(const FT_Vector *c, const FT_Vector *p, void *cc)
{
OutlineData *data = (OutlineData *) cc;
SBezier sb = SBezier::From(
Transform(data, data->px, data->py),
Transform(data, c->x, c->y),
Transform(data, p->x, p->y));
data->beziers->l.Add(&sb);
data->px = p->x;
data->py = p->y;
return 0;
}
static int CubicTo(const FT_Vector *c1, const FT_Vector *c2, const FT_Vector *p, void *cc)
{
OutlineData *data = (OutlineData *) cc;
SBezier sb = SBezier::From(
Transform(data, data->px, data->py),
Transform(data, c1->x, c1->y),
Transform(data, c2->x, c2->y),
Transform(data, p->x, p->y));
data->beziers->l.Add(&sb);
data->px = p->x;
data->py = p->y;
return 0;
}
void TtfFont::PlotString(const std::string &str,
SBezierList *sbl, Vector origin, Vector u, Vector v)
{
ssassert(fontFace != NULL, "Expected font face to be loaded");
FT_Outline_Funcs outlineFuncs;
outlineFuncs.move_to = MoveTo;
outlineFuncs.line_to = LineTo;
outlineFuncs.conic_to = ConicTo;
outlineFuncs.cubic_to = CubicTo;
outlineFuncs.shift = 0;
outlineFuncs.delta = 0;
FT_Pos dx = 0;
for(char32_t cid : ReadUTF8(str)) {
uint32_t gid = FT_Get_Char_Index(fontFace, cid);
if (gid == 0) {
dbp("freetype: CID-to-GID mapping for CID 0x%04x failed: %s; using CID as GID",
cid, ft_error_string(gid));
gid = cid;
}
/*
* Stupid hacks:
* - if we want fake-bold, use FT_Outline_Embolden(). This actually looks
* quite good.
* - if we want fake-italic, apply a shear transform [1 s s 1 0 0] here using
* FT_Set_Transform. This looks decent at small font sizes and bad at larger
* ones, antialiasing mitigates this considerably though.
*/
if(int fterr = FT_Load_Glyph(fontFace, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING)) {
dbp("freetype: cannot load glyph for GID 0x%04x: %s",
gid, ft_error_string(fterr));
return;
}
/* A point that has x = xMin should be plotted at (dx0 + lsb); fix up
* our x-position so that the curve-generating code will put stuff
* at the right place.
*
* There's no point in getting the glyph BBox here - not only can it be
* needlessly slow sometimes, but because we're about to render a single glyph,
* what we want actually *is* the CBox.
*
* This is notwithstanding that this makes extremely little sense, this
* looks like a workaround for either mishandling the start glyph on a line,
* or as a really hacky pseudo-track-kerning (in which case it works better than
* one would expect! especially since most fonts don't set track kerning).
*/
FT_BBox cbox;
FT_Outline_Get_CBox(&fontFace->glyph->outline, &cbox);
FT_Pos bx = dx - cbox.xMin;
// Yes, this is what FreeType calls left-side bearing.
// Then interchangeably uses that with "left-side bearing". Sigh.
bx += fontFace->glyph->metrics.horiBearingX;
OutlineData data = {};
data.origin = origin;
data.u = u;
data.v = v;
data.beziers = sbl;
data.factor = 1.0 / capHeight;
data.bx = bx;
if(int fterr = FT_Outline_Decompose(&fontFace->glyph->outline, &outlineFuncs, &data)) {
dbp("freetype: bezier decomposition failed (gid %d): %s",
gid, ft_error_string(fterr));
}
// And we're done, so advance our position by the requested advance
// width, plus the user-requested extra advance.
dx += fontFace->glyph->advance.x;
}
}
double TtfFont::AspectRatio(const std::string &str) {
ssassert(fontFace != NULL, "Expected font face to be loaded");
// We always request a unit size character, so the aspect ratio is the same as advance length.
double dx = 0;
for(char32_t chr : ReadUTF8(str)) {
uint32_t gid = FT_Get_Char_Index(fontFace, chr);
if (gid == 0) {
dbp("freetype: CID-to-GID mapping for CID 0x%04x failed: %s; using CID as GID",
chr, ft_error_string(gid));
}
if(int fterr = FT_Load_Glyph(fontFace, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING)) {
dbp("freetype: cannot load glyph (GID 0x%04x): %s",
gid, ft_error_string(fterr));
break;
}
dx += (double)fontFace->glyph->advance.x / capHeight;
}
return dx;
}
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