Previously, get_inheritable_object would always try to find the object
and throw an error if it couldn't. The spec tells us that some page
attributes, like CropBox, are optional but also inheritable. Others,
like the media box and resources, are technically required by the spec,
but omitted by some documents.
In both cases, we are now able to search for inheritable objects and
find a suitable replacement if there wasn't one.
This class had slightly confusing semantics and the added weirdness
doesn't seem worth it just so we can say "." instead of "->" when
iterating over a vector of NNRPs.
This patch replaces NonnullRefPtrVector<T> with Vector<NNRP<T>>.
DeprecatedFlyString relies heavily on DeprecatedString's StringImpl, so
let's rename it to A) match the name of DeprecatedString, B) write a new
FlyString class that is tied to String.
PDF allows for named destinations to be provided as string. These can be
either found in the Dests dictionary in the document catalogue (as
already implemented), or in the Name Tree specified by the Dests key in
the Names dictionary of the document catalogue (missing).
This commit adds this missing case. Once the named destination is found
in the name tree, its value is interpreted just like in the first case,
so a new utility method encapsulates the common behavior.
Name Trees are hierarchical, string-keyed, sorted-by-key dictionary
structures in PDF where each node (except the root) specifies the bounds
of the values it holds, and either its kids (more nodes) or the
key/value pairs it contains.
This commit implements a series of lookup calls for finding a key in
such name trees. This implementation follows the tree as needed on each
lookup, but if that becomes inefficient in the long run we can switch to
creating a HashMap with all the contents, which as a drawback will
require more memory.
Destination arrays contain a page number, a mode name, and parameters
specific to that mode. In many cases these parameters can be set to
"null", which our code wasn't taking into consideration.
This commit parses these parameters taking into account whether they are
null or actual numbers, and stores them as Optional<float> instead of
plain floats. The parameters are not yet used anywhere else other than
when formatting a Destination object, so the change is fairly small.
The Value previously stored corresponded to a Reference to a Page object
in the PDF document. This isn't useful information, since what we want
to display at the end of the day is the page an outline item refers to.
This commit changes the page member on OutlineItem to be a Optional<u32>
(some destinations don't necessarily refer to a Page), which we resolve
while building OutlineItems.
While OutlineItem had a parent field, it was never populated nor used.
This commit populates it when possible (no parent means the OutlineItem
is a top-level item).
While the Outline Items making up the document's Outline have all sorts
of cross-references (parent, first/last chlid, next/previous sibling,
etc), not all documents out there have fully-consistent references. Our
implementation already discarded some of that information too (e.g.,
/Parent and /Prev were never read), and trusted that /First and /Next
were good enough to traverse the whole hierarchy.
Where the current implementation failed was in assuming that /Last was
also a good source of information. There are documents out there were
/Last also points to dead ends, and were therefore causing a crash when
we verified that the last child found on a chain was the /Last child
declared by the parent. To fix this I'm simply removing the check, and
simplifying the function call to remove any references to /Last. This
way we affirm our commitment to /First and /Next as the main sources of
information.
This will make it easier to support both string types at the same time
while we convert code, and tracking down remaining uses.
One big exception is Value::to_string() in LibJS, where the name is
dictated by the ToString AO.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
The Parser class is now a generic PDF object parser, of which the new
DocumentParser class derives. DocumentParser now takes over all
functions relating to linearization, pages, xref and trailer handling.
This allows the use of multiple parsers in the same document's
context, which will be needed in order to handle PDF object streams.
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
Security handlers manage encryption and decription of PDF files. The
standard security handler uses RC4/MD5 to perform its crypto (AES as
well, but that is not yet implemented).
Our existing implementation did not check the element type of the other
pointer in the constructors and move assignment operators. This meant
that some operations that would require explicit casting on raw pointers
were done implicitly, such as:
- downcasting a base class to a derived class (e.g. `Kernel::Inode` =>
`Kernel::ProcFSDirectoryInode` in Kernel/ProcFS.cpp),
- casting to an unrelated type (e.g. `Promise<bool>` => `Promise<Empty>`
in LibIMAP/Client.cpp)
This, of course, allows gross violations of the type system, and makes
the need to type-check less obvious before downcasting. Luckily, while
adding the `static_ptr_cast`s, only two truly incorrect usages were
found; in the other instances, our casts just needed to be made
explicit.
The Parser should hold information relevant for parsing, whereas the
Document should hold information relevant for displaying pages.
With this in mind, there is no reason for the Document to hold the
xref table and trailer. These objects have been moved to the Parser,
which allows the Parser to expose less public methods (which will be
even more evident once linearized PDFs are supported).
IndirectValueRef is so simple that it can be stored directly in the
Value class instead of being heap allocated.
As the comment in Value says, however, in theory the max bits needed to
store is 48 (16 for the generation index and 32(?) for the object
index), but 32 should be good enough for now. We can increase it to u64
later if necessary.
We now follow nested page tree nodes to find all of the actual
page dicts, whereas previously we just assumed the root level
page tree node contained all of the page children directly.
This commit introduces the ability to parse the document catalog dict,
as well as the page tree and individual pages. Pages obviously aren't
fully parsed, as we won't care about most of the fields until we
start actually rendering PDFs.
One of the primary benefits of the PDF format is laziness. PDFs are
not meant to be parsed all at once, and the same is true for pages.
When a Document is constructed, it builds a map of page number to
object index, but it does not fetch and parse any of the pages. A page
is only parsed when a caller requests that particular page (and is
cached going forwards).
Additionally, this commit also adds an object_cast function which
logs bad casts if DEBUG_PDF is set. Additionally, utility functions
were added to ArrayObject and DictObject to get all types of objects
from the collections to avoid having to manually cast.
This commit adds a parser as well as the Reader class, which serves
as a utility to aid in reading the PDF both forwards and in reverse.
The parser currently is capable of reading xref tables, as well as
all values. We don't really do anything with any of this information,
however.
