With the exception of `glyphsIds` the length of the other segments can be trivially determined upfront, which is obvious in hindsight. This way unnecessary allocations can be avoided when building the "cmap" table.
This helps reduce the amount of boilerplate code needed in multiple spots throughout the font code, and more importantly it'll help when building TrueType tables whose final size is non-trivial to compute upfront.
Compared to the other TrueType table building functions, see previous patches, these ones are not trivial to convert to use TypedArrays properly.
However, in order to simplify the `OpenTypeFileBuilder` implementation a little bit we can at least have these functions return TypedArray data.
This helper function only had a single call-site, and it's easily replaced with a `DataView` method.
Additionally, to hopefully make future re-factoring easier, create a `DataView` for each TrueType table.
With the changes in PR 21072 the `string16` helper is no longer being used when building the "hmtx" table, which accidentally removed the development mode assert.
After the changes in PR 20197 the code in the `TranslatedFont.prototype.send` method is not all that readable[1] given how it handles e.g. the `charProcOperatorList` data used with Type3 fonts.
Since this is the only spot where `Font.prototype.exportData` is used, it seems much simpler to move the `compileFontInfo` call there and *directly* return the intended data rather than messing with it after the fact.
Finally, while it doesn't really matter, the patch flips the order of the `charProcOperatorList` and `extra` properties throughout the code-base since the former is used with Type3 fonts while the latter (effectively) requires that debugging is enabled.
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[1] I had to re-read it twice, also looking at all the involved methods, in order to convince myself that it's actually correct.
This method is only used with loops, and it should be a tiny bit more efficient to use an iterator directly rather than first iterating through the underlying data to create a temporary `Array` that we finally iterate through at the call-site.
*Please note:* As port of these changes the chars/glyph caches, on the `Font` instances, are changed to use `Map`s rather than Objects.
Currently the `customNames` are read one byte at a time, in a loop, and at every iteration converted to a string.
This can be replaced with the `BaseStream.prototype.getString` method, which didn't exist back when this function was written.
This PR serializes font data into an ArrayBuffer
that is then transfered from the worker to the
main thread. It's more efficient than the current
solution which clones the "export data" object
which includes the font data as a Uint8Array.
It prepares us to switch to a SharedArrayBuffer
in the future, which would allow us to share
the font data with multiple agents, which would be
crucial for the upcoming "renderer" worker.
Previously we'd only do this for Type1/CFF fonts, see e.g. PR 6736, since the font-program may update the /FontMatrix.
However, it seems that we should do this unconditionally to account for fonts with non-default /FontMatrix-entries in the font-dictionary (which seem to be pretty rare).
None of the "composite", "subtype", or "type" properties are normally used on the main-thread and/or in the API, hence there's no need to include them in the exported font-data by default.
Given that these properties may still be useful when debugging, and that `debugger.mjs` actually relies on the "type" property, they will instead only be sent to the main-thread when the `fontExtraProperties` API-option is used.
These options are needed in the `FontFaceObject` class, and indirectly in `FontLoader` as well, which means that we currently need to pass them around manually in the API.
Given that the options are (obviously) available on the worker-thread, it's very easy to just provide them when creating `Font`-instances and then send them as part of the exported font-data. This way we're able to simplify the code (primarily on the main-thread), and note that `Font`-instances even had a `disableFontFace`-field already (but it wasn't properly initialized).
In the affected font the total number of mapping-entries is `1142348`, and no less than `997473` of them are duplicates.
Given that every duplicate causes a lot of Array elements to be moved this becomes extremely inefficient, which we can avoid by keeping track of seen `charCode`s and directly build the final mappings-Array instead.
Given that we handle non-embedded Calibri fonts as "mapped to standard font", we really ought to be able to use the same glyph mapping as for an actual standard font.
Note that this actually improves consistency in the code, given how we already handle such fonts if they happen to be of the `CIDFontType2` type; see b47c7eca83/src/core/fonts.js (L1186-L1190)
This also required changing the initial `charCodeToGlyphId`-data to an Object, which seems generally correct since it's consistent with existing code in the `src\core\{cff_font, type1_font}.js` files.
This should be a *tiny* bit more efficient, since it avoids parsing substrings that we don't care about.
*Please note:* I cannot find an ESLint rule to enforce this automatically.
For arrow functions that are both simple and short, we can avoid using explicit `return` to shorten them even further without hurting readability.
For the `gulp mozcentral` build-target this reduces the overall size of the output by just under 1 kilo-byte (which isn't a lot but still can't hurt).
