[evince] pdf: Show XMP data if newer than modification date

[Germán Poo-Caamaño <gpoo src gnome org>]

commit 548dff664efc890c10d3fb94518430b31fef5adb
Author: Evangelos Rigas <erigas rnd2 org>
Date:   Thu Dec 6 22:51:04 2018 +0000

    pdf: Show XMP data if newer than modification date
    
    From the PDF reference, under section H .3 in Appendix H.,
    if the metadata date stamp is equal to or later than the
    document modification date recorded in the document
    information dictionary, the metadata stream can be taken
    as authoritative.

 backend/pdf/ev-poppler.cc | 97 ++++++++++++++++++++++++++---------------------
 1 file changed, 53 insertions(+), 44 deletions(-)
---
diff --git a/backend/pdf/ev-poppler.cc b/backend/pdf/ev-poppler.cc
index 8f2e9804..8dc0948a 100644
--- a/backend/pdf/ev-poppler.cc
+++ b/backend/pdf/ev-poppler.cc
@@ -846,10 +846,10 @@ pdf_document_get_dates_from_metadata (GTime *result, xmlXPathContextPtr xpathCtx
                g_free (datestr);
        }
 
-       if (createdate != NULL) {
+       if (metadate != NULL) {
                datestr = g_strdup_printf ("%s", metadate);
                g_time_val_from_iso8601 (datestr, &tmp_time);
-               result[1] = (GTime)tmp_time.tv_sec;
+               result[2] = (GTime)tmp_time.tv_sec;
                g_free (datestr);
        }
 
@@ -957,7 +957,7 @@ pdf_document_parse_metadata (const gchar    *metadata,
        gchar             *subject;
        gchar             *creatortool;
        gchar             *producer;
-       GTime             dates[3] = {0};
+       GTime              dates[3] = {0};
 
        doc = xmlParseMemory (metadata, strlen (metadata));
        if (doc == NULL)
@@ -969,55 +969,64 @@ pdf_document_parse_metadata (const gchar    *metadata,
                return;         /* invalid xpath context */
        }
 
-       fmt = pdf_document_get_format_from_metadata (xpathCtx);
-       if (fmt != NULL) {
-               g_free (info->format);
-               info->format = fmt;
-       }
+       pdf_document_get_dates_from_metadata (dates, xpathCtx);
+       /* From PDF spec, if the PDF modified date is newer than metadata date,
+        * it indicates that the file was edited by a non-XMP aware software.
+        * Then, the information dictionary is considered authoritative and the
+        * XMP metadata should not be displayed. */
+       if (dates[2] >= info->modified_date) {
+
+               fmt = pdf_document_get_format_from_metadata (xpathCtx);
+               if (fmt != NULL) {
+                       g_free (info->format);
+                       info->format = fmt;
+               }
 
-       author = pdf_document_get_author_from_metadata (xpathCtx);
-       if (author != NULL) {
-               g_free (info->author);
-               info->author = author;
-       }
+               author = pdf_document_get_author_from_metadata (xpathCtx);
+               if (author != NULL) {
+                       g_free (info->author);
+                       info->author = author;
+               }
 
-       keywords = pdf_document_get_keywords_from_metadata (xpathCtx);
-       if (keywords != NULL) {
-               g_free (info->keywords);
-               info->keywords = keywords;
-       }
+               keywords = pdf_document_get_keywords_from_metadata (xpathCtx);
+               if (keywords != NULL) {
+                       g_free (info->keywords);
+                       info->keywords = keywords;
+               }
 
-       title = pdf_document_get_title_from_metadata (xpathCtx);
-       if (title != NULL) {
-               g_free (info->title);
-               info->title = title;
-       }
+               title = pdf_document_get_title_from_metadata (xpathCtx);
+               if (title != NULL) {
+                       g_free (info->title);
+                       info->title = title;
+               }
 
-       subject = pdf_document_get_subject_from_metadata (xpathCtx);
-       if (subject != NULL) {
-               g_free (info->subject);
-               info->subject = subject;
-       }
+               subject = pdf_document_get_subject_from_metadata (xpathCtx);
+               if (subject != NULL) {
+                       g_free (info->subject);
+                       info->subject = subject;
+               }
 
-       creatortool = pdf_document_get_creatortool_from_metadata (xpathCtx);
-       if (creatortool != NULL) {
-               g_free (info->creator);
-               info->creator = creatortool;
-       }
+               creatortool = pdf_document_get_creatortool_from_metadata (xpathCtx);
+               if (creatortool != NULL) {
+                       g_free (info->creator);
+                       info->creator = creatortool;
+               }
 
-       producer = pdf_document_get_producer_from_metadata (xpathCtx);
-       if (producer != NULL) {
-               g_free (info->producer);
-               info->producer = producer;
-       }
+               producer = pdf_document_get_producer_from_metadata (xpathCtx);
+               if (producer != NULL) {
+                       g_free (info->producer);
+                       info->producer = producer;
+               }
 
-       pdf_document_get_dates_from_metadata (dates, xpathCtx);
-       if (dates[0] != 0){
-               info->modified_date = dates[0];
-       }
 
-       if (dates[1] != 0) {
-               info->creation_date = dates[1];
+               if (dates[0] != 0){
+                       info->modified_date = dates[0];
+               }
+
+               if (dates[1] != 0) {
+                       info->creation_date = dates[1];
+               }
+
        }
 
        info->license = pdf_document_get_license_from_metadata (xpathCtx);