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[feat] Add support for loading OpenType fonts from memory. #82

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[feat] Add support for loading OpenType fonts from memory. #82

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04afbd6
[feat] Ability to load fonts from memory :)
notmarek Jan 17, 2025
cb71b42
Move otInit into add_ot_font_data
notmarek Jan 17, 2025
54c575f
Typo 1
notmarek Jan 17, 2025
2002b1f
typo 2
notmarek Jan 17, 2025
b1ef069
typo 3
notmarek Jan 17, 2025
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149 changes: 95 additions & 54 deletions fbink.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5624,19 +5624,10 @@ static __attribute__((cold)) const char*
}
}

// Load OT fonts for fbink_add_ot_font & fbink_add_ot_font_v2
// Load OT fonts for add_ot_font
static __attribute__((cold)) int
add_ot_font(const char* filename, FONT_STYLE_T style, FBInkOTFonts* restrict ot_fonts)
add_ot_font_data(const unsigned char* data, FONT_STYLE_T style, FBInkOTFonts* restrict ot_fonts)
{
# ifdef FBINK_FOR_KOBO
// NOTE: Bail if we were passed a Kobo system font, as they're obfuscated,
// and some of them risk crashing stbtt because of bogus data...
const char blacklist[] = "/usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/";
if (!strncmp(filename, blacklist, sizeof(blacklist) - 1)) {
WARN("Cannot use font `%s`: it's an obfuscated Kobo system font", filename + sizeof(blacklist) - 1);
return ERRCODE(EXIT_FAILURE);
}
# endif

// Init libunibreak the first time we're called
if (!otInit) {
Expand All @@ -5645,70 +5636,34 @@ static __attribute__((cold)) int
}
otInit = true;

// Open font from given path, and load into buffer
FILE* f = fopen(filename, "r" STDIO_CLOEXEC);
unsigned char* restrict data = NULL;
if (!f) {
PFWARN("fopen: %m");
otInit = false;
return ERRCODE(EXIT_FAILURE);
} else {
const int fd = fileno(f);
struct stat st;
if (fstat(fd, &st) == -1) {
PFWARN("fstat: %m");
fclose(f);
otInit = false;
return ERRCODE(EXIT_FAILURE);
}
data = calloc((size_t) st.st_size, sizeof(*data));
if (!data) {
PFWARN("Error allocating font data buffer: %m");
fclose(f);
otInit = false;
return ERRCODE(EXIT_FAILURE);
}
if (fread(data, 1U, (size_t) st.st_size, f) < (size_t) st.st_size || ferror(f) != 0) {
free(data);
fclose(f);
otInit = false;
WARN("Error reading font file `%s`", filename);
return ERRCODE(EXIT_FAILURE);
}
fclose(f);
}
stbtt_fontinfo* font_info = calloc(1U, sizeof(stbtt_fontinfo));
stbtt_fontinfo* font_info = calloc(1U, sizeof(stbtt_fontinfo));
if (!font_info) {
PFWARN("Error allocating stbtt_fontinfo struct: %m");
free(data);
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ditto

return ERRCODE(EXIT_FAILURE);
}
// First, check if we can actually find a recognizable font format in the data...
const int fontcount = stbtt_GetNumberOfFonts(data);
if (fontcount == 0) {
free(data);
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ditto

free(font_info);
WARN("File `%s` doesn't appear to be a valid or supported font", filename);
WARN("File doesn't appear to be a valid or supported font");
return ERRCODE(EXIT_FAILURE);
} else if (fontcount > 1) {
LOG("Font file `%s` appears to be a font collection containing %d fonts, but we'll only use the first one!",
filename,
LOG("Font file appears to be a font collection containing %d fonts, but we'll only use the first one!",
fontcount);
}
// Then, get the offset to the first font
const int fontoffset = stbtt_GetFontOffsetForIndex(data, 0);
if (fontoffset == -1) {
free(data);
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@NiLuJe NiLuJe Jan 17, 2025 •
edited
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In the same vein, this needs to be free(font_info->data);

Which implies that we take ownership of the pointer, which might be a problem for your usecase (e.g., pointer to static content), so this may need to be more complex to add a way to say "nope, this data is immutable, don't ever try to free it".

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Weeelll, except font_info->data only exists after stbtt_InitFont ;p.

The point about ownership still stands, though ;p.

free(font_info);
WARN("File `%s` doesn't appear to contain valid font data at offset %d", filename, fontoffset);
WARN("File doesn't appear to contain valid font data at offset %d", fontoffset);
return ERRCODE(EXIT_FAILURE);
}
// And finally, initialize that font
// NOTE: We took the long way 'round to try to avoid crashes on invalid data...
if (!stbtt_InitFont(font_info, data, fontoffset)) {
free(font_info->data);
free(font_info);
WARN("Error initialising font `%s`", filename);
WARN("Error initialising font.");
return ERRCODE(EXIT_FAILURE);
}
// Assign the current font to its appropriate FBInkOTFonts struct member, depending on the style specified by the caller.
Expand Down Expand Up @@ -5741,13 +5696,65 @@ static __attribute__((cold)) int
default:
free(font_info->data);
free(font_info);
WARN("Cannot load font `%s`: requested style (%d) is invalid!", filename, style);
WARN("Cannot load font: requested style (%d) is invalid!", style);
return ERRCODE(EXIT_FAILURE);
}

ELOG("Font `%s` loaded for style '%s'", filename, font_style_to_string(style));
ELOG("Font loaded for style '%s'", font_style_to_string(style));
return EXIT_SUCCESS;
}

// Load OT fonts from a file for fbink_add_ot_font & fbink_add_ot_font_v2
static __attribute__((cold)) int
add_ot_font(const char* filename, FONT_STYLE_T style, FBInkOTFonts* restrict ot_fonts)
{
# ifdef FBINK_FOR_KOBO
// NOTE: Bail if we were passed a Kobo system font, as they're obfuscated,
// and some of them risk crashing stbtt because of bogus data...
const char blacklist[] = "/usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/";
if (!strncmp(filename, blacklist, sizeof(blacklist) - 1)) {
WARN("Cannot use font `%s`: it's an obfuscated Kobo system font", filename + sizeof(blacklist) - 1);
return ERRCODE(EXIT_FAILURE);
}
# endif


// Open font from given path, and load into buffer
FILE* f = fopen(filename, "r" STDIO_CLOEXEC);
unsigned char* restrict data = NULL;
if (!f) {
PFWARN("fopen: %m");
otInit = false;
return ERRCODE(EXIT_FAILURE);
} else {
const int fd = fileno(f);
struct stat st;
if (fstat(fd, &st) == -1) {
PFWARN("fstat: %m");
fclose(f);
otInit = false;
return ERRCODE(EXIT_FAILURE);
}
data = calloc((size_t) st.st_size, sizeof(*data));
if (!data) {
PFWARN("Error allocating font data buffer: %m");
fclose(f);
otInit = false;
return ERRCODE(EXIT_FAILURE);
}
if (fread(data, 1U, (size_t) st.st_size, f) < (size_t) st.st_size || ferror(f) != 0) {
free(data);
fclose(f);
otInit = false;
WARN("Error reading font file `%s`", filename);
return ERRCODE(EXIT_FAILURE);
}
fclose(f);
}
int result = add_ot_font_data(data, style, ot_fonts);
free(data);
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That's a problem ;).

(The data is still live, stbtt doesn't make a copy, it just keeps a reference to that same pointer).

return result;
}
#endif // FBINK_WITH_OPENTYPE

// Load font from given file path. Up to four font styles may be used by FBInk at any given time.
Expand All @@ -5764,6 +5771,20 @@ int
#endif // FBINK_WITH_OPENTYPE
}

// Load font from memory. Up to four font styles may be used by FBInk at any given time.
int
fbink_add_ot_font_from_memory(const unsigned char* data UNUSED_BY_MINIMAL, FONT_STYLE_T style UNUSED_BY_MINIMAL)
{
#ifdef FBINK_WITH_OPENTYPE
// Legacy variant, using the global otFonts
LOG("Loading font data in the global font pool . . .");
return add_ot_font_data(data, style, &otFonts);
#else
WARN("OpenType support is disabled in this FBInk build");
return ERRCODE(ENOSYS);
#endif // FBINK_WITH_OPENTYPE
}

// Load font from given file path. Up to four font styles may be used per FBInkOTConfig instance.
int
fbink_add_ot_font_v2(const char* filename UNUSED_BY_MINIMAL,
Expand All @@ -5788,6 +5809,26 @@ int
#endif // FBINK_WITH_OPENTYPE
}

// Load font from memory. Up to four font styles may be used per FBInkOTConfig instance.
int fbink_add_ot_font_from_memory_v2(const unsigned char* data UNUSED_BY_MINIMAL, FONT_STYLE_T style UNUSED_BY_MINIMAL, FBInkOTConfig *restrict cfg UNUSED_BY_MINIMAL) {
#ifdef FBINK_WITH_OPENTYPE
// Start by allocating an FBInkOTFonts struct, if need be...
if (!cfg->font) {
cfg->font = calloc(1U, sizeof(FBInkOTFonts));
if (!cfg->font) {
PFWARN("Error allocating FBInkOTFonts struct: %m");
return ERRCODE(EXIT_FAILURE);
}
}
// New variant, using a per-FBInkOTConfig instance
LOG("Loading font data in a local FBInkOTFonts instance (%p) . . .", cfg->font);
return add_ot_font_data(data, style, (FBInkOTFonts*) cfg->font);
#else
WARN("OpenType support is disabled in this FBInk build");
return ERRCODE(ENOSYS);
#endif // FBINK_WITH_OPENTYPE
}

#ifdef FBINK_WITH_OPENTYPE
// Free an individual OpenType font structure
static __attribute__((cold)) int
Expand Down
10 changes: 10 additions & 0 deletions fbink.h
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Original file line number Diff line number Diff line change
Expand Up @@ -847,6 +847,11 @@ FBINK_API int fbink_print(int fbfd, const char* restrict string, const FBInkConf
// Which leads me to a final, critical warning:
// NOTE: Don't try to pass non-font files or encrypted/obfuscated font files, because it *will* horribly segfault!
FBINK_API int fbink_add_ot_font(const char* filename, FONT_STYLE_T style) __attribute__((nonnull));

// Same as fbink_add_ot_font, but loads the font from memory instead of a file.
// data: Pointer to the font data in memory.
FBINK_API int fbink_add_ot_font_from_memory(const unsigned char* data, FONT_STYLE_T style) __attribute__((nonnull));

// Same API and behavior, except that the set of fonts being loaded is tied to this specific FBInkOTConfig instance,
// instead of being global.
// In which case, resources MUST be released via fbink_free_ot_fonts_v2()!
Expand All @@ -856,6 +861,11 @@ FBINK_API int fbink_add_ot_font(const char* filename, FONT_STYLE_T style) __attr
FBINK_API int fbink_add_ot_font_v2(const char* filename, FONT_STYLE_T style, FBInkOTConfig* restrict cfg)
__attribute__((nonnull));

// Same as fbink_add_ot_font_v2, but loads the font from memory instead of a file.
// data: Pointer to the font data in memory.
FBINK_API int fbink_add_ot_font_from_memory_v2(const unsigned char* data, FONT_STYLE_T style, FBInkOTConfig* restrict cfg)
__attribute__((nonnull));

// Free all loaded OpenType fonts. You MUST call this when you have finished all OT printing.
// NOTE: Safe to call even if no fonts were actually loaded.
FBINK_API int fbink_free_ot_fonts(void);
Expand Down