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macOS: Fix fallback font rendering for bold/italic text not working f…
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…or some symbols that are present in the Menlo regular face but not the bold/italic faces

Fixes #8282
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@kovidgoyal
kovidgoyal committed Feb 3, 2025
1 parent 66747c0 commit 5edfed0
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Showing 2 changed files with 36 additions and 48 deletions.
2 changes: 2 additions & 0 deletions docs/changelog.rst
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Expand Up @@ -112,6 +112,8 @@ Detailed list of changes

- Speed up rendering of box drawing characters by moving the implementation to native code

- macOS: Fix fallback font rendering for bold/italic text not working for some symbols that are present in the Menlo regular face but not the bold/italic faces (:iss:`8282`)

0.39.1 [2025-02-01]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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82 changes: 34 additions & 48 deletions kitty/core_text.m
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Original file line number Diff line number Diff line change
Expand Up @@ -359,11 +359,9 @@ static CTFontRef nerd_font(CGFloat sz) {
for (CFIndex i = 0; i < count; i++) {
CTFontDescriptorRef descriptor = (CTFontDescriptorRef)CFArrayGetValueAtIndex(fonts, i);
CTFontRef new_font = CTFontCreateWithFontDescriptor(descriptor, CTFontGetSize(current_font), NULL);
if (!is_last_resort_font(new_font)) {
if (font_can_render_cell(new_font, lc)) {
ans = new_font;
break;
}
if (!is_last_resort_font(new_font) && font_can_render_cell(new_font, lc)) {
ans = new_font;
break;
}
CFRelease(new_font);
}
Expand All @@ -380,53 +378,41 @@ static CTFontRef nerd_font(CGFloat sz) {

static CTFontRef
find_substitute_face(CFStringRef str, CTFontRef old_font, const ListOfChars *lc) {
// CTFontCreateForString returns the original font when there are combining
// diacritics in the font and the base character is in the original font,
// so we have to check each character individually
CFIndex len = CFStringGetLength(str), start = 0, amt = len;
while (start < len) {
CTFontRef new_font = CTFontCreateForString(old_font, str, CFRangeMake(start, amt));
if (amt == len && len != 1) amt = 1;
else start++;
if (new_font == old_font) { CFRelease(new_font); continue; }
if (!new_font || is_last_resort_font(new_font)) {
if (new_font) CFRelease(new_font);
if (is_private_use(lc->chars[0])) {
// CoreTexts fallback font mechanism does not work for private use characters
new_font = manually_search_fallback_fonts(old_font, lc);
if (new_font) return new_font;
}
return NULL;
}
return new_font;
// CoreText's fallback system has various problems:
// 1) CTFontCreateForString returns the original font when there are combining
// diacritics in the text and the base character is in the original font.
// 2) Fallback does not work for PUA characters
CTFontRef new_font = CTFontCreateForString(old_font, str, CFRangeMake(0, CFStringGetLength(str)));
if (!new_font || is_last_resort_font(new_font) || !font_can_render_cell(new_font, lc)) {
if (new_font) CFRelease(new_font);
// CoreText's fallback font mechanism does not work for private use characters, it also fails
// in specific circumstances, such as:
return manually_search_fallback_fonts(old_font, lc);
}
return NULL;
return new_font;
}

static CTFontRef
apply_styles_to_fallback_font(CTFontRef original_fallback_font, bool bold, bool italic) {
apply_styles_to_fallback_font(CTFontRef original_fallback_font, bool bold, bool italic, const ListOfChars *lc) {
if (!original_fallback_font || (!bold && !italic) || is_last_resort_font(original_fallback_font)) return original_fallback_font;
CTFontDescriptorRef original_descriptor = CTFontCopyFontDescriptor(original_fallback_font);
RAII_CoreFoundation(CTFontDescriptorRef, original_descriptor, CTFontCopyFontDescriptor(original_fallback_font));
if (!original_descriptor) return original_fallback_font;
// We cannot set kCTFontTraitMonoSpace in traits as if the original
// fallback font is Zapf Dingbats we get .AppleSystemUIFontMonospaced as
// the new fallback
CTFontSymbolicTraits traits = 0;
if (bold) traits |= kCTFontTraitBold;
if (italic) traits |= kCTFontTraitItalic;
CTFontDescriptorRef descriptor = CTFontDescriptorCreateCopyWithSymbolicTraits(original_descriptor, traits, traits);
CFRelease(original_descriptor);
if (descriptor) {
CTFontRef ans = CTFontCreateWithFontDescriptor(descriptor, CTFontGetSize(original_fallback_font), NULL);
CFRelease(descriptor);
if (!ans) return original_fallback_font;
CFStringRef new_name = CTFontCopyFamilyName(ans);
CFStringRef old_name = CTFontCopyFamilyName(original_fallback_font);
bool same_family = cf_string_equals(new_name, old_name);
/* NSLog(@"old: %@ new: %@", old_name, new_name); */
CFRelease(new_name); CFRelease(old_name);
if (same_family) { CFRelease(original_fallback_font); return ans; }
CFRelease(ans);
}
RAII_CoreFoundation(CTFontDescriptorRef, descriptor, CTFontDescriptorCreateCopyWithSymbolicTraits(original_descriptor, traits, traits));
if (!descriptor) return original_fallback_font;
CTFontRef ans = CTFontCreateWithFontDescriptor(descriptor, CTFontGetSize(original_fallback_font), NULL);
if (!ans) return original_fallback_font;
RAII_CoreFoundation(CFStringRef, new_name, CTFontCopyFamilyName(ans));
RAII_CoreFoundation(CFStringRef, old_name, CTFontCopyFamilyName(original_fallback_font));
bool same_family = cf_string_equals(new_name, old_name);
/* NSLog(@"old: %@ new: %@", old_name, new_name); */
if (same_family && font_can_render_cell(ans, lc)) { CFRelease(original_fallback_font); return ans; }
CFRelease(ans);
return original_fallback_font;
}

Expand All @@ -444,20 +430,20 @@ static CTFontRef nerd_font(CGFloat sz) {
create_fallback_face(PyObject *base_face, const ListOfChars *lc, bool bold, bool italic, bool emoji_presentation, FONTS_DATA_HANDLE fg) {
CTFace *self = (CTFace*)base_face;
RAII_CoreFoundation(CTFontRef, new_font, NULL);
#define search_for_fallback() \
CFStringRef str = lc_as_fallback(lc); \
if (str == NULL) return PyErr_NoMemory(); \
new_font = find_substitute_face(str, self->ct_font, lc); \
CFRelease(str);
RAII_CoreFoundation(CFStringRef, str, lc_as_fallback(lc));
if (str == NULL) return PyErr_NoMemory();

if (emoji_presentation) {
new_font = CTFontCreateWithName((CFStringRef)@"AppleColorEmoji", self->scaled_point_sz, NULL);
if (!new_font || !glyph_id_for_codepoint_ctfont(new_font, lc->chars[0])) {
if (new_font) CFRelease(new_font);
search_for_fallback();
new_font = find_substitute_face(str, self->ct_font, lc);
}
}
else { search_for_fallback(); new_font = apply_styles_to_fallback_font(new_font, bold, italic); }
else {
new_font = find_substitute_face(str, self->ct_font, lc);
new_font = apply_styles_to_fallback_font(new_font, bold, italic, lc);
}
if (new_font == NULL) Py_RETURN_NONE;
RAII_PyObject(postscript_name, convert_cfstring(CTFontCopyPostScriptName(new_font), true));
if (!postscript_name) return NULL;
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