OpenSystemsDevelopment / qpdf

Replace data member oh with accessors.

Remove redundant overloads from QPDFObjGen::set.

This improves indentation of long strings. This commit also fixes some
trailing whitespace in ChangeLog.

The code accepted values other than /Yes but still used /Yes as the
checked value instead of obeying the normal appearance dictionary.

Add new convenience class QPDFObjGen::Guard

Also, inline method and add optional parameter error_msg.

(patrepl and cleanpatch are my own utilities)

patrepl s/PointerHolder/std::shared_ptr/g {include,libqpdf}/qpdf/*.hh
patrepl s/PointerHolder/std::shared_ptr/g libqpdf/*.cc
patrepl s/make_pointer_holder/std::make_shared/g libqpdf/*.cc
patrepl s/make_array_pointer_holder/QUtil::make_shared_array/g libqpdf/*.cc
patrepl s,qpdf/std::shared_ptr,qpdf/PointerHolder, **/*.cc **/*.hh
git restore include/qpdf/PointerHolder.hh
cleanpatch
./format-code

Add comments to force line breaks, parenthesize function arguments
that are contatenated strings, etc. -- these kinds of changes improve
clang-format's results and also cause emacs cc-mode to match
clang-format. After this type of change, most of the time, when
clang-format and emacs disagree, clang-format is better.

Run this:

for i in  **/*.cc **/*.c **/*.h **/*.hh; do
  clang-format < $i >| $i.new && mv $i.new $i
done

This is so it will fit on one line after a qtest upgrade allows us to
split lines.

If not found in the field hierarchy, /Q and /DA are supposed to be
looked up in the document-level form dictionary. /DR is supposed to
only come from the document dictionary.

* Several assertions in linearization were not always true; change
  them to run time errors
* Handle a few cases of uninitialized objects
* Handle pages with no contents when doing form operations
* Handle invalid page tree nodes when traversing pages

This makes all integer type conversions that have potential data loss
explicit with calls that do range checks and raise an exception. After
this commit, qpdf builds with no warnings when -Wsign-conversion
-Wconversion is used with gcc or clang or when -W3 -Wd4800 is used
with MSVC. This significantly reduces the likelihood of potential
crashes from bogus integer values.

There are some parts of the code that take int when they should take
size_t or an offset. Such places would make qpdf not support files
with more than 2^31 of something that usually wouldn't be so large. In
the event that such a file shows up and is valid, at least qpdf would
raise an error in the right spot so the issue could be legitimately
addressed rather than failing in some weird way because of a silent
overflow condition.

Bounding box X coordinates could be truncated, causing them to be off
by a fraction of a point. This was most likely not visible, but it was
still wrong.

If we end up using our fallback font size when generating appearances
for text fields, reflect that in the Tf operator used in the
appearance stream.

When generating appearance streams for variable text annotations,
properly handle the cases of there being no appearance dictionary, no
appearance stream, or an appearance stream with no BMC..EMC marker.