Template 2 is needed by some symbols in 0000372.pdf page 11 and
0000857.pdf pages 1-4. Implement the others too while here. (The
mentioned pages in those two PDFs also use the "end of stripe" segment,
so they still don't render yet.
We still don't support EXTTEMPLATE.
Instead of fetching a generic set of metrics for each glyph, only fetch
the advance when that's all we need.
This is extremely hot in LibWeb text layout, where it makes a nice dent.
Although it has some interesting properties, SipHash is brutally slow
compared to our previous hash function. Since its introduction, it has
been highly visible in every profile of doing anything interesting with
LibJS or LibWeb.
By switching back, we gain a 10x speedup for 32-bit hashes, and "only"
a 3x speedup for 64-bit hashes.
This comes out to roughly 1.10x faster HashTable insertion, and roughly
2.25x faster HashTable lookup. Hashing is no longer at the top of
profiles and everything runs measurably faster.
For security-sensitive hash tables with user-controlled inputs, we can
opt into SipHash selectively on a case-by-case basis. The vast majority
of our uses don't fit that description though.
...and make text_region_decoding_procedure() call it.
generic_refinement_region_decoding_procedure() still just returns
"unimplemented", so no behavior change yet.
Text segments using refinement are still rejected later, by
text_region_decoding_procedure(). But we deserialize the input data now,
and the error when this feature is used is now slightly different.
This was added in commit f2663f477f as a
partial implementation of what is now LibWeb's forgiving Base64 decoder.
All use cases within LibWeb that require whitespace skipping now use
that implementation instead.
Removing this feature from AK allows us to know the exact output size of
a decoded Base64 string. We can still trim whitespace at the start and
end of the input though; for example, this is useful when reading from a
file that may have a newline at the end of the file.
Caught by clang-format-17. Note that clang-format-16 is fine with this
as well (it leaves the const placement alone), it just doesn't perform
the formatting to east-const itself.
This is a fetching AO and is only used by LibWeb in the context of fetch
tasks. Move it to LibWeb with other fetch methods.
The main reason for this is that it requires the use of other LibWeb AOs
such as the forgiving Base64 decoder and MIME sniffing. These AOs aren't
available within LibURL.
Fixes delayed repainting in the following case:
1. Style or layout invalidation triggers html event loop processing.
2. Event loop processing does nothing because there is no rendering
opportunity.
3. Style or layout change won't be reflected until something else
triggers event loop processing
If we already have a FlyString instantiated for the given string,
look that up and return it instead of making a temporary String just to
use as a key into the FlyString table.
Before this change, the global FlyString table looked like this:
HashMap<StringView, Detail::StringBase>
After this change, we have:
HashTable<Detail::StringData const*, FlyStringTableHashTraits>
The custom hash traits are used to extract the stored hash from
StringData which avoids having to rehash the StringView repeatedly like
we did before.
This necessitated a handful of smaller changes to make it work.
It seems to do the right thing already, and nothing in the spec says
not to do this as far as I can tell.
With this, we can finally decode the test input from #23659.
See f391c7822d for a similar change for generic regions and
lossless generic regions.
Text segments conceptually store (x,y,id) triples. (x,y) are a
coordinate, and id refers to an id from a symbol segment.
A text segment has the effect of drawing some of the bitmaps stored
in a symbol segment to the output bitmap.
For example, the symbol segment might contain a small bitmap that
happens to look like the letter 'A', and the text segment might
draw that everywhere a scanned page has an 'A'. (The JBIG2 format
only treats it as an abstract bitmap. It doesn't know that this
small bitmap is an 'A'.)
This is missing support for many things:
* Huffman-coded input (not used in practice)
* Symbol refinement
* Transposed symbols
* Colors (not used in practice)
Still, we now have basic symbol/text segment support. This is enough
to decode the downloadable PDF here:
https://www.google.com/books/edition/Paradise_Lost/6qdbAAAAQAAJ
It doesn't lead to any progression on my 1000 file test PDF set.
The 7 files in there that use JBIG2 with symbol and text segments
now fail to load for other reasons (4 need symbol refinement for
text segments, one needs end-of-stripe segment support, one needs
support for symbol segments referring to other segments).
(And possibly, many other PDFs from Google Books, but that's the
only one I've tried so far.)
This extracts the bitbuffer combining code we had into a new function
composite_bitbuffer() and adds the following features:
* Real support for combination operators (which also lets us allow black
as background color again, even if that's never used in practice)
* Clipping support (not used here yet, but will be needed elsewhere
soon)
We're going to need this for text segment handling.
No behavior change.
A symbol segment defines a bunch of small bitmaps and associates them
with numeric IDs.
This only implements reading symbols encoded with the arithmetic coder.
It does not support huffman coding. (In practice, everything seems to
use arithmetic coding.)
Support for refinement or aggregate coding isn't implemented yet.
Support for retaining bitmap coding contexts isn't implemented yet.
Support for symbol segments referring to other symbol segments isn't
implemented yet.
But all produce diagnostics if encountered, so we won't forget about
them. (I haven't seen either being used in the wild.)
No visible behavior change yet, but with JBIG2_DEBUG turned on,
it produces all kinds of debug output.
The symbol segment decoding procedure will read generic regions
that aren't at a byte boundary, and that share contexts across
several regions.
No behavior change.
The existing ArithmeticEncoder (from Annex E) reads one bit at a
time.
ArithmeticIntegerDecoder (from Annex A) builds on top of that to
read integer values.
This will be used by both the symbol segment and the text segment
readers.
(This does not yet implement the IAID decoding procedure in A.3.
We only need that one in the text segment decoder at the moment,
and it's pretty small, so I'll put it inline there for now.)
Not used yet, so no behavior change yet.
