Minor improvements when writing duplicate tags.

samples/exifprint.cpp

@@ -28,7 +28,9 @@ try {
     }
     Exiv2::ExifData::const_iterator end = exifData.end();
     for (Exiv2::ExifData::const_iterator i = exifData.begin(); i != end; ++i) {
-        std::cout << std::setw(44) << std::setfill(' ') << std::left
+        std::cout << std::setw(3) << std::right
+                  << i->idx() << " "
+                  << std::setw(44) << std::setfill(' ') << std::left
                   << i->key() << " "
                   << "0x" << std::setw(4) << std::setfill('0') << std::right
                   << std::hex << i->tag() << " "

src/tiffcomposite.cpp

@@ -1402,7 +1402,8 @@ namespace Exiv2 {
     {
         assert(lhs != 0);
         assert(rhs != 0);
-        return lhs->tag() < rhs->tag();
+        if (lhs->tag() != rhs->tag()) return lhs->tag() < rhs->tag();
+        return lhs->idx() < rhs->idx();
     }
 
     TiffComponent::AutoPtr newTiffDirectory(uint16_t tag,

src/tiffcomposite_int.hpp

@@ -245,6 +245,12 @@ namespace Exiv2 {
                  their implementation of writeImage().
          */
         uint32_t sizeImage() const;
+        /*!
+          @brief Return the unique id of the entry in the image.
+         */
+        // Todo: This is only implemented in TiffEntryBase. It is needed here so that
+        //       we can sort components by tag and idx. Something is not quite right.
+        virtual int idx()        const { return 0; }
         //@}
 
     protected:
@@ -426,7 +432,7 @@ namespace Exiv2 {
         /*!
           @brief Return the unique id of the entry in the image
          */
-        int idx()                const { return idx_; }
+        virtual int idx()        const { return idx_; }
         /*!
           @brief Return a pointer to the binary representation of the
                  value of this component.

src/tiffvisitor.cpp

@@ -646,6 +646,11 @@ namespace Exiv2 {
                 ed = &(*pos);
             }
         }
+        else {
+            // For intrusive writing, the index is used to preserve the order of
+            // duplicate tags
+            object->idx_ = ed->idx();
+        }
         if (ed) {
             const EncoderFct fct = findEncoderFct_(make_, object->tag(), object->group());
             if (fct) {