encodeString has the same surrogate-pair guard that encodeToXmlString had
before #21526: `unicode > 0xd7ff && (unicode < 0xe000 || unicode > 0xfffd)`.
That predicate is also true for U+FFFE and U+FFFF, which are single UTF-16
code units, not surrogate pairs. The extra `i++` then steps over the
character that follows them, so it is silently dropped from the
font-encoded output used when saving or printing a PDF.
For example, encoding a string that is U+FFFF followed by "A", with a font
that has a glyph for both, returns an encoded result ending in "A" on this
branch but drops the "A" on master.
Same fix as #21526: the correct test for a real surrogate pair is
`unicode > 0xffff`, since codePointAt only returns a value at or above
0x10000 for an actual pair. This keeps existing behavior for real surrogate
pairs (e.g. emoji) and the U+FFFD boundary, and only stops the character
after U+FFFE/U+FFFF from being dropped.
Added test/unit/fonts_spec.js, since Font.prototype.encodeString had no
direct unit test. It calls the method on a minimal fake `this` (only
toUnicode/cMap are read), since building a full Font requires a complete
properties/font-file setup that this bug doesn't depend on.
There have been lots of problems with trying to map glyphs to their unicode
values. It's more reliable to just use the private use areas so the browser's
font renderer doesn't mess with the glyphs.
Using the private use area for all glyphs did highlight other issues that this
patch also had to fix:
* small private use area - Previously, only the BMP private use area was used
which can't map many glyphs. Now, the (much bigger) PUP 16 area can also be
used.
* glyph zero not shown - Browsers will not use the glyph from a font if it is
glyph id = 0. This issue was less prevalent when we mapped to unicode values
since the fallback font would be used. However, when using the private use
area, the glyph would not be drawn at all. This is illustrated in one of the
current test cases (issue #8234) where there's an "ä" glyph at position
zero. The PDF looked like it rendered correctly, but it was actually not
using the glyph from the font. To properly show the first glyph it is always
duplicated and appended to the glyphs and the maps are adjusted.
* supplementary characters - The private use area PUP 16 is 4 bytes, so
String.fromCodePoint must be used where we previously used
String.fromCharCode. This is actually an issue that should have been fixed
regardless of this patch.
* charset - Freetype fails to load fonts when the charset size doesn't match
number of glyphs in the font. We now write out a fake charset with the
correct length. This also brought up the issue that glyphs with seac/endchar
should only ever write a standard charset, but we now write a custom one.
To get around this the seac analysis is permanently enabled so those glyphs
are instead always drawn as two glyphs.
Please see http://eslint.org/docs/rules/object-shorthand.
Unfortunately, based on commit 9276d1dcd9, it seems that we still need to maintain compatibility with old Node.js versions, hence certain files/directories that are executed in Node.js are currently exempt from this rule.
Furthermore, since the files specific to the Chromium extension are not run through Babel, the `/extensions/chromium/` directory is also exempt from this rule.
When adding new entries to `ProblematicCharRanges`, you have to be careful to not make any mistakes since that could cause glyph mapping issues.
Currently the existing reference tests should probably help catch any errors, but based on experience I think that having a unit-test which specifically checks `ProblematicCharRanges` would be both helpful and timesaving when modifying/reviewing changes to this code.
Hence this patch which adds a function (and unit-test) that is used to validate the entries in `ProblematicCharRanges`, and also checks that we don't accidentally add more character ranges than the Private Use Area can actually contain.
The way that the validation code, and thus the unit-test, is implemented also means that we have an easy way to tell how much of the Private Use Area is potentially utilized by re-mapped characters.
