*Note:* This is similar to PR 19525, which did the same thing for the OpenJPEG decoder.
The advantages of doing this are:
- The same JBig2 decoder is used regardless of WASM being supported or not, which means consistent rendering.
- The old `Jbig2Image` implementation has various bugs and missing features.
- Less code that needs to be maintained in the PDF.js project, since both the CCITT and the JBig2 decoder is replaced.
The disadvantage of doing this is:
- Slightly larger bundle size, however the effect is limited since a fair amount of PDF.js code can be removed. For the `gulp mozcentral` target the size increase is approximately 54 kilo-bytes (which is small compared to the 452 kilo-bytes for the JS version of the OpenJPEG decoder).
Instrument JS files on-the-fly via babel-plugin-istanbul when --coverage
or --coverage-per-test is passed, producing an aggregate lcov/HTML report
at the end of the run. A persistent PDFWorker accumulates worker-thread
coverage alongside the main-thread coverage, collected via a new
GetWorkerCoverage message handler.
With --coverage-per-test, an inverted index
(build/coverage/per-test-index.json) is also built as tests run, mapping
each hit source line and function name to the numeric IDs of the tests
that exercised it, keeping the output compact. The new
`gulp test_search --code=file::line_or_function` tool queries the index,
and passing --code to browsertest pre-filters the test run to only those
tests.
Coverage output formats are selectable via --coverage-formats (default:
info; also accepts html, json, text, cobertura, clover).
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.
Currently the code only updates the position when the length is defined, and it seems that this has "always" been wrong. Originally I believe that the `ChunkedStream` class was essentially a copy of the `Stream` class, and that implementation had the same problem until PR 20593.
Hopefully there's no code that relies on the current incorrect behaviour[1], since testing every aspect of the `ChunkedStream` implementation can be tricky given that these things are timing dependant.
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[1] If there are, fixing those call-sites may be as easy calling `ChunkedStream.prototype.reset`.
Nowadays there's a lot of places in the code-base where we need to initialize or reset bounding boxes. Rather than spelling this out repeatedly, this patch adds new `Array`/`Float32Array` constants that can be copied or used as-is where appropriate.
