Simplify reference management in SkPDF
Prior to this change, SkPDFObject subclasses were required
to track their resources separately from the document
structure. (An object has a resource if it depends, via an
indirect reference, on another object). This led to a lot
of extra code to duplicate effort. I replace the
getResources() function with the much simpler addResources()
function. I only define a non-trivial addResources() method
on arrays, dictionaries, and indirect object references.
All other specialized classes simply rely on their parent
class's implementation.
SkPDFObject::addResources() works by recursively walking the
directed graph of object (direct and indirect) references
and adding resources to a set. It doesn't matter that there
are closed loops in the graph, since we check the set before
walking down a branch.
- Add SkPDFObject::addResources() virtual function, with
four implementations
- Remove SkPDFObject::getResources() virtual function and
all implementations.
- Remove SkPDFObject::GetResourcesHelper()
- Remove SkPDFObject::AddResourceHelper()
- In SkPDFCatalog::findObjectIndex(), add an object to the
catalog if it doesn't exist yet.
- SkPDFCatalog::setSubstitute() no longer sets up resources
- SkPDFDocument.cpp no longer needs the Streamer object
- SkPDFDocument.cpp calls fDocCatalog->addResources to build
the resource list.
- SkPDFFont::addResource() removed
- All SkPDF-::fResource sets removed (they are redundant).
- removed SkPDFImage::addSMask() function
- SkPDFResourceDict::getReferencedResources() removed.
Motivation: this removes quite a bit of code and makes the
objects slightly slimmer in memory. Most importantly, this
will lead the way towards removing SkPDFObject's inheritance
from SkRefCnt, which will greatly simplify everything.
Testing: I usually test changes to the PDF backend by
comparing checksums of PDF files rendered from GMs and SKPs
before and after the change. This change both re-orders and
re-numbers the indirect PDF objects. I used the qpdf
program to normalize the PDFs and then compared the
normalized outputs from before and after the change; they
matched.
Review URL: https://codereview.chromium.org/870333002
19 files changed