How can I tell freetype to use a fallback font when a string does contain a character that is not present in the Font I'm using as a default?
I need to render non-latin glyphs correctly in my application.
Do I have to manage a fallback myself?
If so: how do I detect if there is a missing glyph in a given string?
I'm sorry, I don't know if you need to handle fallback yourself, but my guess would be that you do. As for how to detect if there is missing glyph, you could use this method: FT_Get_Char_index If it returns 0, it means symbol was not found.
The GNU Unifont can serve as a fallback font for every codepoint in the Basic Multilingual Plane (BMP), which would be 0x0000-0xFFFF. That should cover the vast majority of what you might encounter. Available for download here (archive).
The Unicode Last Resort font can serve as a final fallback for every codepoint in all of the planes. These glyphs only show broad categories. Available for download here.
It looks like you would have to detect the absence of a glyph with FT_Get_Char_Index() as SMart explained, and in those cases turn to Unifont or the Last Resort font.
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Not sure if SO is the best place for this question, but don't know where else to ask.
Is there any way to transform a svg like this one for ex: (https://svgsilh.com/image/1775543.html) into something that i can use inside an editor with copy/paste like this one? 🦄
No, because the unicorn emoticon is one example of a character. And just as with letters, digits, and punctuation, the appearance of emoticons and other plain-text symbols is decided by fonts.
LSerni wrote the following:
The reason you can "copy and paste" that icon is that the icon already has a UTF-8 code and your editor is UTF-8 aware. And this is why the same emoticon is slightly different between Apple, Android and so on: it's because it's always code XYZ, but code XYZ is rendered with different icons on different platforms.
But that's not entirely correct. The difference in rendering lies more in the font than in the operating system that displays emoticons. Unless the font supplies its own version of a symbol, that symbol will usually be supplied by the font specified by default by the operating system, and different operating systems supply different symbol fonts.
I wrote a script which parses information from PDF files and outputs it to HTML. It's written in Python, using pdfminer.
On some text segments, the font style can have semantic significance. For instance: bold, italic and color should trigger different behavior. Pdfminer provides scripts with the font name, but not the color, and it has a number of other issues; so I'm working on a Swift version of that program, using Apple's PDFKit, to extract the same features.
I now find that I have the opposite problem. While PDFKit makes it easy to retrieve color, retrieving the original font name seems to be non-obvious. PDFSelection objects have an attributedString property, but for fonts that are not installed on my computer, the NSFont object is Helvetica. Of course, the fonts in question are fairly expensive, and acquiring a copy just for this purpose would be poor form.
Short of dropping to CGPDFContentStream (which is way too big of a hammer for what I want to get), is there a way of getting the original font name? I know in advance what the fonts are going to be, can I use that to my advantage?
PDFKit seems to use the standard font lookup system and then falls back on some default, so this can be resolved by spoofing the font to ensure that PDFKit doesn't need to fall back. Inspecting the document, I was able to identify that it uses the following fonts (referenced with their PostScript name):
"NeoSansIntel"
"NeoSansIntelMedium"
"NeoSansIntel,Italic"
I used a free font creation utility to create dummy fonts with these PostScript names, and I added them to my app bundle. I then used CTFontManagerRegisterFontsForURLs to load these fonts (in the .process scope), and now PDFKit uses these fonts for attributed strings that need them.
Of course, the fonts are bogus and this is useless for rendering. However, it works perfectly for the purpose of identifying text that uses these font.
I have found this letter / character in facebook, but how can this have a color? is just insane for me, look this: ✔️
Added image (From Firefox on windows)
It's not an ASCII character, it's likely an emoji. Emoji are part of Unicode and the actual glyph displayed to the user is open to interpretation by the platform displaying it. The spec suggests a name/description, but the implementation varies.
So while you may see a colored check mark, I see black & white. Other times, a single glyph will have multiple styles made available on a particular platform; for example, I can select multiple "skin" tones when I use a smiley face on my iPhone, but your Android device may only show a generic one.
Edit: The image edited into the original post is a perfect example. Using Chrome on Windows, I see a black check mark. The screenshot from Firefox shows green.
The symbols used here aren't ascii-encoded. They use the much more vast range of Unicode encoding. Ascii(extended) is restricted to a 256 symbol set.
The unicode interpretation for symbols/glyphs(small pictorial representation)(these ticks aren't characters), can vary for different platforms as some the range of unicode is open for usage and isn't set as global.
Which is why, while the unicode encryption remains the same for every device irrespective, the decryption is differently interpreted by different devices/online-platforms, allowing us to perceive either a coloured or a black symbol.
I'm doing color transformations on glyphs rendered with CTFontDrawGlyphs, but I do not want to do those transformations to the emoji glyphs, since they have already a meaningful color information.
So, when I have a CTRun of glyphs, can I detect if it is actually emoji/color font?
I can do a string compare to the postscript name with "AppleColorEmoji", but seems awfully wasteful to do all the time, and somewhat hacky if there ever happens to be another font with the same features.
Ah, I can get the symbolic traits with CTFontGetSymbolicTraits, and check for kCTFontTraitColorGlyphs (or kCTFontColorGlyphsTrait), which, while undocumented, is available in the public headers.
This could probably also be asked as "Is kCTKernAttributeName a misnomer?"
I need to change the letter spacing/tracking of some text in iOS. (The font I'm using is a little too tight at small sizes.) There are core graphics routines that will change character spacing, but those routines don't handle Unicode. There are other core graphics routines that are defined in terms of glyphs but those seem like a world of hurt, among other things, not having the safety net of reverting back to system fonts for glyphs that don't exist in my font.
So core text seems like the way to do this and core text supports kCTKernAttributeName on CFAttributedString. I think this will do what I want, though this really isn't kerning since kerning is a generally a character-pair attribute and this (appears to be, from the docs) just a uniform adjustment to the glyph advance for all glyphs, i.e., tracking.
If anyone knows before I go down the rather painful path of converting to the core text API ...
kCTKernAttribute name should do what you want. Setting it over a range of text adjusts the inter-glyph spacing consistently, irrespective of the specific glyphs.
I think part of the problem is that kerning seems to have been a virtual synonym of tracking (it's still just "adjust the spacing between (letters or characters) in a piece of text to be printed" in the dictionary that comes with OS X), and is now adopting just the meaning of pair kerning because of the redundancy. Probably an etymologist would be better placed to comment on that side of things...