SkPDF: add basic metadata support

src/doc/SkDocument_PDF.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDocument.h"
 #include "SkPDFCanon.h"
 #include "SkPDFDevice.h"
 #include "SkPDFFont.h"
 #include "SkPDFStream.h"
 #include "SkPDFTypes.h"
+#include "SkPDFUtils.h"
 #include "SkStream.h"
 
+class SkPDFDict;
+
 static void emit_pdf_header(SkWStream* stream) {
     stream->writeText("%PDF-1.4\n%");
     // The PDF spec recommends including a comment with four bytes, all
     // with their high bits set.  This is "Skia" with the high bits set.
     stream->write32(0xD3EBE9E1);
     stream->writeText("\n");
 }
 
 static void emit_pdf_footer(SkWStream* stream,
                             const SkPDFObjNumMap& objNumMap,
                             const SkPDFSubstituteMap& substitutes,
                             SkPDFObject* docCatalog,
                             int64_t objCount,
-                            int32_t xRefFileOffset) {
+                            int32_t xRefFileOffset,
+                            SkPDFDict* info) {
     SkPDFDict trailerDict;
     // TODO(vandebo): Linearized format will take a Prev entry too.
     // TODO(vandebo): PDF/A requires an ID entry.
     trailerDict.insertInt("Size", int(objCount));
     trailerDict.insertObjRef("Root", SkRef(docCatalog));
+    SkASSERT(info);
+    trailerDict.insertObjRef("Info", SkRef(info));
 
     stream->writeText("trailer\n");
     trailerDict.emitObject(stream, objNumMap, substitutes);
     stream->writeText("\nstartxref\n");
     stream->writeBigDecAsText(xRefFileOffset);
     stream->writeText("\n%%EOF");
 }
 
 static void perform_font_subsetting(
         const SkTDArray<const SkPDFDevice*>& pageDevices,
@@ skipping 104 matching lines @@
         nextRoundNodes.rewind();
         treeCapacity *= kNodeSize;
     } while (curNodes.count() > 1);
 
     pageTree->push(curNodes[0]);  // Transfer reference.
     if (rootNode) {
         *rootNode = curNodes[0];
     }
 }
 
+struct Metadata {
+    SkTArray<SkDocument::Attribute> fInfo;
+    SkAutoTDelete<const SkTime::DateTime> fCreation;
+    SkAutoTDelete<const SkTime::DateTime> fModified;
+};
+
+static SkString pdf_date(const SkTime::DateTime& dt) {
+    int timeZoneMinutes = SkToInt(dt.fTimeZoneMinutes);
+    char timezoneSign = timeZoneMinutes >= 0 ? '+' : '-';
+    int timeZoneHours = SkTAbs(timeZoneMinutes) / 60;
+    timeZoneMinutes = SkTAbs(timeZoneMinutes) % 60;
+    return SkStringPrintf(
+            "D:%04u%02u%02u%02u%02u%02u%c%02d'%02d'",
+            static_cast<unsigned>(dt.fYear), static_cast<unsigned>(dt.fMonth),
+            static_cast<unsigned>(dt.fDay), static_cast<unsigned>(dt.fHour),
+            static_cast<unsigned>(dt.fMinute),
+            static_cast<unsigned>(dt.fSecond), timezoneSign, timeZoneHours,
+            timeZoneMinutes);
+}
+
+SkPDFDict* create_document_information_dict(const Metadata& metadata) {
+    SkAutoTUnref<SkPDFDict> dict(new SkPDFDict);
+    static const char* keys[] = {
+        "Title", "Author", "Subject", "Keywords", "Creator" };
+    for (const char* key : keys) {
+        for (const SkDocument::Attribute& keyValue : metadata.fInfo) {
+            if (keyValue.fKey.equals(key)) {
+                dict->insertString(key, keyValue.fValue);
+            }
+        }
+    }
+    dict->insertString("Producer", "Skia/PDF");
+    if (metadata.fCreation) {
+        dict->insertString("CreationDate", pdf_date(*metadata.fCreation.get()));
+    }
+    if (metadata.fModified) {
+        dict->insertString("ModDate", pdf_date(*metadata.fModified.get()));
+    }
+    return dict.detach();
+}
+
 static bool emit_pdf_document(const SkTDArray<const SkPDFDevice*>& pageDevices,
+                              const Metadata& metadata,
                               SkWStream* stream) {
     if (pageDevices.isEmpty()) {
         return false;
     }
 
     SkTDArray<SkPDFDict*> pages;
     SkAutoTUnref<SkPDFDict> dests(new SkPDFDict);
 
     for (int i = 0; i < pageDevices.count(); i++) {
         SkASSERT(pageDevices[i]);
@@ skipping 21 matching lines @@
     outputIntent->insertString("OutputConditionIdentifier", "sRGB");
     SkAutoTUnref<SkPDFArray> intentArray(new SkPDFArray);
     intentArray->appendObject(SkRef(outputIntent.get()));
     docCatalog->insertObject("OutputIntent", intentArray.detach());
     */
 
     // Build font subsetting info before proceeding.
     SkPDFSubstituteMap substitutes;
     perform_font_subsetting(pageDevices, &substitutes);
 
+    SkAutoTUnref<SkPDFDict> infoDict(
+            create_document_information_dict(metadata));
     SkPDFObjNumMap objNumMap;
+    if (objNumMap.addObject(infoDict)) {
+        infoDict->addResources(&objNumMap, substitutes);
+    }
     if (objNumMap.addObject(docCatalog.get())) {
         docCatalog->addResources(&objNumMap, substitutes);
     }
     size_t baseOffset = stream->bytesWritten();
     emit_pdf_header(stream);
     SkTDArray<int32_t> offsets;
     for (int i = 0; i < objNumMap.objects().count(); ++i) {
         SkPDFObject* object = objNumMap.objects()[i];
         size_t offset = stream->bytesWritten();
         // This assert checks that size(pdf_header) > 0 and that
@@ skipping 14 matching lines @@
 
     stream->writeText("xref\n0 ");
     stream->writeDecAsText(objCount);
     stream->writeText("\n0000000000 65535 f \n");
     for (int i = 0; i < offsets.count(); i++) {
         SkASSERT(offsets[i] > 0);
         stream->writeBigDecAsText(offsets[i], 10);
         stream->writeText(" 00000 n \n");
     }
     emit_pdf_footer(stream, objNumMap, substitutes, docCatalog.get(), objCount,
-                    xRefFileOffset);
+                    xRefFileOffset, infoDict);
 
     // The page tree has both child and parent pointers, so it creates a
     // reference cycle.  We must clear that cycle to properly reclaim memory.
     for (int i = 0; i < pageTree.count(); i++) {
         pageTree[i]->clear();
     }
     pageTree.safeUnrefAll();
     pages.unrefAll();
     return true;
 }
@@ skipping 30 matching lines @@
     }
     if (notSubsettableCount) {
         *notSubsettableCount = notSubsettable;
 
     }
     if (notEmbeddableCount) {
         *notEmbeddableCount = notEmbeddable;
     }
 }
 #endif
+
+template <typename T> static T* clone(const T* o) { return o ? new T(*o) : nullptr; }
 ////////////////////////////////////////////////////////////////////////////////
 
 namespace {
 class SkDocument_PDF : public SkDocument {
 public:
     SkDocument_PDF(SkWStream* stream,
                    void (*doneProc)(SkWStream*, bool),
                    SkScalar rasterDpi)
         : SkDocument(stream, doneProc)
         , fRasterDpi(rasterDpi) {}
@@ skipping 21 matching lines @@
 
     void onEndPage() override {
         SkASSERT(fCanvas.get());
         fCanvas->flush();
         fCanvas.reset(nullptr);
     }
 
     bool onClose(SkWStream* stream) override {
         SkASSERT(!fCanvas.get());
 
-        bool success = emit_pdf_document(fPageDevices, stream);
+        bool success = emit_pdf_document(fPageDevices, fMetadata, stream);
         fPageDevices.unrefAll();
         fCanon.reset();
         return success;
     }
 
     void onAbort() override {
         fPageDevices.unrefAll();
         fCanon.reset();
     }
 
+    void setMetadata(const SkTArray<SkDocument::Attribute>& info,
+                     const SkTime::DateTime* creationDate,
+                     const SkTime::DateTime* modifiedDate) override {
+        fMetadata.fInfo = info;
+        fMetadata.fCreation.reset(clone(creationDate));
+        fMetadata.fModified.reset(clone(modifiedDate));
+    }
+
 private:
     SkPDFCanon fCanon;
     SkTDArray<const SkPDFDevice*> fPageDevices;
     SkAutoTUnref<SkCanvas> fCanvas;
     SkScalar fRasterDpi;
+    Metadata fMetadata;
 };
 }  // namespace
 ///////////////////////////////////////////////////////////////////////////////
 
 SkDocument* SkDocument::CreatePDF(SkWStream* stream, SkScalar dpi) {
     return stream ? new SkDocument_PDF(stream, nullptr, dpi) : nullptr;
 }
 
 SkDocument* SkDocument::CreatePDF(const char path[], SkScalar dpi) {
     SkFILEWStream* stream = new SkFILEWStream(path);
     if (!stream->isValid()) {
         delete stream;
         return nullptr;
     }
     auto delete_wstream = [](SkWStream* stream, bool) { delete stream; };
     return new SkDocument_PDF(stream, delete_wstream, dpi);
 }