SkPDF: add basic metadata support

src/doc/SkDocument_PDF.cpp

Index: src/doc/SkDocument_PDF.cpp
diff --git a/src/doc/SkDocument_PDF.cpp b/src/doc/SkDocument_PDF.cpp
index 4ea9d89dd7d83cc938617e1d892c420f76eead27..fb22f18ec5da5af7807935476b07f29783ef4651 100644
--- a/src/doc/SkDocument_PDF.cpp
+++ b/src/doc/SkDocument_PDF.cpp
@@ -11,8 +11,11 @@
 #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
@@ -26,12 +29,15 @@ static void emit_pdf_footer(SkWStream* stream,
                             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);
@@ -156,7 +162,49 @@ static void generate_page_tree(const SkTDArray<SkPDFDict*>& pages,
     }
 }
 
+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;
@@ -198,7 +246,12 @@ static bool emit_pdf_document(const SkTDArray<const SkPDFDevice*>& pageDevices,
     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);
     }
@@ -233,7 +286,7 @@ static bool emit_pdf_document(const SkTDArray<const SkPDFDevice*>& pageDevices,
         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.
@@ -284,6 +337,8 @@ void GetCountOfFontTypes(
     }
 }
 #endif
+
+template <typename T> static T* clone(const T* o) { return o ? new T(*o) : nullptr; }
 ////////////////////////////////////////////////////////////////////////////////
 
 namespace {
@@ -325,7 +380,7 @@ protected:
     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;
@@ -336,11 +391,20 @@ protected:
         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
 ///////////////////////////////////////////////////////////////////////////////