Unified interface for complex properties like pictures (#94)

Provides a dynamic interface for properties which cannot be represented
with simple strings, e.g. pictures. The keys of such properties can
be queried using `complexPropertyKeys()`, which could return for example
["PICTURE"]. The property can then be read using
`complexProperties("PICTURE")`, which will return a list of variant maps
containing the picture data and attributes. Adding a picture is as
easy as

    t->setComplexProperties("PICTURE", {
      {
        {"data", data},
        {"pictureType", "Front Cover"},
        {"mimeType", "image/jpeg"}
      }
    });

taglib/mpeg/id3v2/frames/attachedpictureframe.h

@@ -27,6 +27,7 @@
 #define TAGLIB_ATTACHEDPICTUREFRAME_H
 
 #include "taglib_export.h"
+#include "tpicturetype.h"
 #include "id3v2frame.h"
 #include "id3v2header.h"
 
@@ -52,50 +53,7 @@ namespace TagLib {
       /*!
        * This describes the function or content of the picture.
        */
-      enum Type {
-        //! A type not enumerated below
-        Other              = 0x00,
-        //! 32x32 PNG image that should be used as the file icon
-        FileIcon           = 0x01,
-        //! File icon of a different size or format
-        OtherFileIcon      = 0x02,
-        //! Front cover image of the album
-        FrontCover         = 0x03,
-        //! Back cover image of the album
-        BackCover          = 0x04,
-        //! Inside leaflet page of the album
-        LeafletPage        = 0x05,
-        //! Image from the album itself
-        Media              = 0x06,
-        //! Picture of the lead artist or soloist
-        LeadArtist         = 0x07,
-        //! Picture of the artist or performer
-        Artist             = 0x08,
-        //! Picture of the conductor
-        Conductor          = 0x09,
-        //! Picture of the band or orchestra
-        Band               = 0x0A,
-        //! Picture of the composer
-        Composer           = 0x0B,
-        //! Picture of the lyricist or text writer
-        Lyricist           = 0x0C,
-        //! Picture of the recording location or studio
-        RecordingLocation  = 0x0D,
-        //! Picture of the artists during recording
-        DuringRecording    = 0x0E,
-        //! Picture of the artists during performance
-        DuringPerformance  = 0x0F,
-        //! Picture from a movie or video related to the track
-        MovieScreenCapture = 0x10,
-        //! Picture of a large, coloured fish
-        ColouredFish       = 0x11,
-        //! Illustration related to the track
-        Illustration       = 0x12,
-        //! Logo of the band or performer
-        BandLogo           = 0x13,
-        //! Logo of the publisher (record company)
-        PublisherLogo      = 0x14
-      };
+      DECLARE_PICTURE_TYPE_ENUM(Type)
 
       /*!
        * Constructs an empty picture frame.  The description, content and text

taglib/mpeg/id3v2/id3v2tag.cpp

@@ -37,6 +37,8 @@
 #include "id3v2footer.h"
 #include "id3v2synchdata.h"
 #include "id3v1genres.h"
+#include "frames/attachedpictureframe.h"
+#include "frames/generalencapsulatedobjectframe.h"
 #include "frames/textidentificationframe.h"
 #include "frames/commentsframe.h"
 #include "frames/urllinkframe.h"
@@ -451,6 +453,84 @@ PropertyMap ID3v2::Tag::setProperties(const PropertyMap &origProps)
   return PropertyMap(); // ID3 implements the complete PropertyMap interface, so an empty map is returned
 }
 
+StringList ID3v2::Tag::complexPropertyKeys() const
+{
+  StringList keys;
+  if(d->frameListMap.contains("APIC")) {
+    keys.append("PICTURE");
+  }
+  if(d->frameListMap.contains("GEOB")) {
+    keys.append("GENERALOBJECT");
+  }
+  return keys;
+}
+
+List<VariantMap> ID3v2::Tag::complexProperties(const String &key) const
+{
+  List<VariantMap> properties;
+  const String uppercaseKey = key.upper();
+  if(uppercaseKey == "PICTURE") {
+    const FrameList pictures = d->frameListMap.value("APIC");
+    for(const Frame *frame : pictures) {
+      auto picture = static_cast<const AttachedPictureFrame *>(frame);
+      VariantMap property;
+      property.insert("data", picture->picture());
+      property.insert("mimeType", picture->mimeType());
+      property.insert("description", picture->description());
+      property.insert("pictureType",
+        AttachedPictureFrame::typeToString(picture->type()));
+      properties.append(property);
+    }
+  }
+  else if(uppercaseKey == "GENERALOBJECT") {
+    const FrameList geobs = d->frameListMap.value("GEOB");
+    for(const Frame *frame : geobs) {
+      auto geob = static_cast<const GeneralEncapsulatedObjectFrame *>(frame);
+      VariantMap property;
+      property.insert("data", geob->object());
+      property.insert("mimeType", geob->mimeType());
+      property.insert("description", geob->description());
+      property.insert("fileName", geob->fileName());
+      properties.append(property);
+    }
+  }
+  return properties;
+}
+
+bool ID3v2::Tag::setComplexProperties(const String &key, const List<VariantMap> &value)
+{
+  const String uppercaseKey = key.upper();
+  if(uppercaseKey == "PICTURE") {
+    removeFrames("APIC");
+
+    for(auto property : value) {
+      auto picture = new AttachedPictureFrame;
+      picture->setPicture(property.value("data").value<ByteVector>());
+      picture->setMimeType(property.value("mimeType").value<String>());
+      picture->setDescription(property.value("description").value<String>());
+      picture->setType(AttachedPictureFrame::typeFromString(
+        property.value("pictureType").value<String>()));
+      addFrame(picture);
+    }
+  }
+  else if(uppercaseKey == "GENERALOBJECT") {
+    removeFrames("GEOB");
+
+    for(auto property : value) {
+      auto geob = new GeneralEncapsulatedObjectFrame;
+      geob->setObject(property.value("data").value<ByteVector>());
+      geob->setMimeType(property.value("mimeType").value<String>());
+      geob->setDescription(property.value("description").value<String>());
+      geob->setFileName(property.value("fileName").value<String>());
+      addFrame(geob);
+    }
+  }
+  else {
+    return false;
+  }
+  return true;
+}
+
 ByteVector ID3v2::Tag::render() const
 {
   return render(ID3v2::v4);

taglib/mpeg/id3v2/id3v2tag.h

@@ -329,6 +329,10 @@ namespace TagLib {
        */
       PropertyMap setProperties(const PropertyMap &) override;
 
+      StringList complexPropertyKeys() const override;
+      List<VariantMap> complexProperties(const String &key) const override;
+      bool setComplexProperties(const String &key, const List<VariantMap> &value) override;
+
       /*!
        * Render the tag back to binary data, suitable to be written to disk.
        */