Use rating from EXIF/XMP where available

rtengine/imagedata.cc

@@ -188,10 +188,18 @@ FrameData::FrameData (rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
         orientation = tag->valueToString ();
     }
 
+    // Look for Rating metadata in the following order:
+    // 1. EXIF
+    // 2. XMP
+    // 3. pp3 sidecar file
     tag = newFrameRootDir->findTagUpward("Rating");
-    if (tag) {
+    if (tag && tag->toInt() != 0) {
         rating = tag->toInt();
     }
+    char sXMPRating[64];
+    if (newFrameRootDir->getXMPTagValue("xmp:Rating", sXMPRating)) {
+        rating = atoi(sXMPRating);
+    }
 
     tag = newFrameRootDir->findTagUpward("MakerNote");
     rtexif::TagDirectory* mnote = nullptr;

rtengine/imagedata.h

@@ -48,8 +48,8 @@ protected:
     double expcomp;
     std::string make, model, serial;
     std::string orientation;
-    std::string lens;
     int rating;
+    std::string lens;
     IIOSampleFormat sampleFormat;
 
     // each frame has the knowledge of "being an"

rtengine/procparams.cc

@@ -2832,7 +2832,10 @@ void ProcParams::setDefaults()
     exif.clear();
     iptc.clear();
 
-    rank = 0;
+    // -1 means that there's no pp3 data with rank yet. In this case, the
+    // embedded Rating metadata should take precedence. -1 should never be
+    // written to pp3 on disk.
+    rank = -1;
     colorlabel = 0;
     inTrash = false;
 

rtgui/thumbnail.cc

@@ -1006,15 +1006,22 @@ void Thumbnail::setFileName (const Glib::ustring &fn)
 
 int Thumbnail::getRank  () const
 {
+    // prefer the user-set rank over the embedded Rating
+    // pparams->rank == -1 means that there is no saved rank yet, so we should
+    // next look for the embedded Rating metadata.
+    if (pparams->rank != -1) {
         return pparams->rank;
+    } else {
+        return cfs.rating;
+    }
 }
 
 void Thumbnail::setRank  (int rank)
 {
     if (pparams->rank != rank) {
         pparams->rank = rank;
-        pparamsValid = true;
     }
+    pparamsValid = true;
 }
 
 int Thumbnail::getColorLabel  () const

rtgui/thumbnail.h

@@ -164,17 +164,8 @@ public:
         return cfs.md5;
     }
 
-    int             getRank  () const
-    {
-        return cfs.rating;
-    }
-    void            setRank  (int rank)
-    {
-        if (cfs.rating != rank) {
-            cfs.rating = rank;
-        }
-        pparamsValid = true; // FIXME-piotr Is this the right way to refresh the cache? Probably not since pparams and cache should be 2 different things
-    }
+    int             getRank  () const;
+    void            setRank  (int rank);
 
     int             getColorLabel  () const;
     void            setColorLabel  (int colorlabel);