Merge #548: Streamline usage of event types, part 1

25 files changed, 385 insertions, 379 deletions

diff --git a/lib/events/accountdataevents.h b/lib/events/accountdataevents.h
index 12f1f00b..ec2f64e3 100644
--- a/lib/events/accountdataevents.h
+++ b/lib/events/accountdataevents.h
@@ -46,27 +46,14 @@ struct JsonObjectConverter<TagRecord> {
 
 using TagsMap = QHash<QString, TagRecord>;
 
-#define DEFINE_SIMPLE_EVENT(_Name, _TypeId, _ContentType, _ContentKey)       \
-    class QUOTIENT_API _Name : public Event {                             \
-    public:                                                                  \
-        using content_type = _ContentType;                                   \
-        DEFINE_EVENT_TYPEID(_TypeId, _Name)                                  \
-        explicit _Name(const QJsonObject& obj) : Event(typeId(), obj) {}     \
-        explicit _Name(const content_type& content)                          \
-            : Event(typeId(), matrixTypeId(),                                \
-                    QJsonObject {                                            \
-                        { QStringLiteral(#_ContentKey), toJson(content) } }) \
-        {}                                                                   \
-        auto _ContentKey() const                                             \
-        {                                                                    \
-            return contentPart<content_type>(#_ContentKey##_ls);             \
-        }                                                                    \
-    };                                                                       \
-    REGISTER_EVENT_TYPE(_Name)                                               \
-    // End of macro
-
-DEFINE_SIMPLE_EVENT(TagEvent, "m.tag", TagsMap, tags)
-DEFINE_SIMPLE_EVENT(ReadMarkerEvent, "m.fully_read", QString, event_id)
-DEFINE_SIMPLE_EVENT(IgnoredUsersEvent, "m.ignored_user_list", QSet<QString>,
+DEFINE_SIMPLE_EVENT(TagEvent, Event, "m.tag", TagsMap, tags)
+DEFINE_SIMPLE_EVENT(ReadMarkerEventImpl, Event, "m.fully_read", QString, eventId)
+class ReadMarkerEvent : public ReadMarkerEventImpl {
+public:
+    using ReadMarkerEventImpl::ReadMarkerEventImpl;
+    [[deprecated("Use ReadMarkerEvent::eventId() instead")]]
+    QString event_id() const { return eventId(); }
+};
+DEFINE_SIMPLE_EVENT(IgnoredUsersEvent, Event, "m.ignored_user_list", QSet<QString>,
                     ignored_users)
 } // namespace Quotient
diff --git a/lib/events/callanswerevent.h b/lib/events/callanswerevent.h
index 8ffe60f2..70292a7a 100644
--- a/lib/events/callanswerevent.h
+++ b/lib/events/callanswerevent.h
@@ -17,10 +17,8 @@ public:
                              const QString& sdp);
     explicit CallAnswerEvent(const QString& callId, const QString& sdp);
 
-    int lifetime() const
-    {
-        return contentPart<int>("lifetime"_ls);
-    } // FIXME: Omittable<>?
+    QUO_CONTENT_GETTER(int, lifetime) // FIXME: Omittable<>?
+
     QString sdp() const
     {
         return contentPart<QJsonObject>("answer"_ls).value("sdp"_ls).toString();
diff --git a/lib/events/callcandidatesevent.h b/lib/events/callcandidatesevent.h
index 74c38f2c..e949f722 100644
--- a/lib/events/callcandidatesevent.h
+++ b/lib/events/callcandidatesevent.h
@@ -23,20 +23,9 @@ public:
                         { { QStringLiteral("candidates"), candidates } })
     {}
 
-    QJsonArray candidates() const
-    {
-        return contentPart<QJsonArray>("candidates"_ls);
-    }
-
-    QString callId() const
-    {
-        return contentPart<QString>("call_id");
-    }
-
-    int version() const
-    {
-        return contentPart<int>("version");
-    }
+    QUO_CONTENT_GETTER(QJsonArray, candidates)
+    QUO_CONTENT_GETTER(QString, callId)
+    QUO_CONTENT_GETTER(int, version)
 };
 
 REGISTER_EVENT_TYPE(CallCandidatesEvent)
diff --git a/lib/events/callinviteevent.h b/lib/events/callinviteevent.h
index 47362b5c..1b1f4f0f 100644
--- a/lib/events/callinviteevent.h
+++ b/lib/events/callinviteevent.h
@@ -16,10 +16,7 @@ public:
     explicit CallInviteEvent(const QString& callId, const int lifetime,
                              const QString& sdp);
 
-    int lifetime() const
-    {
-        return contentPart<int>("lifetime"_ls);
-    } // FIXME: Omittable<>?
+    QUO_CONTENT_GETTER(int, lifetime) // FIXME: Omittable<>?
     QString sdp() const
     {
         return contentPart<QJsonObject>("offer"_ls).value("sdp"_ls).toString();
diff --git a/lib/events/directchatevent.cpp b/lib/events/directchatevent.cpp
index 0ee1f7b0..83bb1e32 100644
--- a/lib/events/directchatevent.cpp
+++ b/lib/events/directchatevent.cpp
@@ -3,8 +3,6 @@
 
 #include "directchatevent.h"
 
-#include <QtCore/QJsonArray>
-
 using namespace Quotient;
 
 QMultiHash<QString, QString> DirectChatEvent::usersToDirectChats() const
diff --git a/lib/events/encryptionevent.cpp b/lib/events/encryptionevent.cpp
index 6272c668..6e994cd4 100644
--- a/lib/events/encryptionevent.cpp
+++ b/lib/events/encryptionevent.cpp
@@ -47,11 +47,12 @@ EncryptionEventContent::EncryptionEventContent(EncryptionType et)
     }
 }
 
-void EncryptionEventContent::fillJson(QJsonObject* o) const
+QJsonObject EncryptionEventContent::toJson() const
 {
-    Q_ASSERT(o);
+    QJsonObject o;
     if (encryption != EncryptionType::Undefined)
-        o->insert(AlgorithmKey, algorithm);
-    o->insert(RotationPeriodMsKey, rotationPeriodMs);
-    o->insert(RotationPeriodMsgsKey, rotationPeriodMsgs);
+        o.insert(AlgorithmKey, algorithm);
+    o.insert(RotationPeriodMsKey, rotationPeriodMs);
+    o.insert(RotationPeriodMsgsKey, rotationPeriodMsgs);
+    return o;
 }
diff --git a/lib/events/encryptionevent.h b/lib/events/encryptionevent.h
index 124ced33..5b5420ec 100644
--- a/lib/events/encryptionevent.h
+++ b/lib/events/encryptionevent.h
@@ -4,12 +4,11 @@
 
 #pragma once
 
-#include "eventcontent.h"
 #include "stateevent.h"
 #include "quotient_common.h"
 
 namespace Quotient {
-class QUOTIENT_API EncryptionEventContent : public EventContent::Base {
+class QUOTIENT_API EncryptionEventContent {
 public:
     enum EncryptionType : size_t { MegolmV1AesSha2 = 0, Undefined };
 
@@ -20,13 +19,12 @@ public:
     {}
     explicit EncryptionEventContent(const QJsonObject& json);
 
+    QJsonObject toJson() const;
+
     EncryptionType encryption;
     QString algorithm;
     int rotationPeriodMs;
     int rotationPeriodMsgs;
-
-protected:
-    void fillJson(QJsonObject* o) const override;
 };
 
 using EncryptionType = EncryptionEventContent::EncryptionType;
diff --git a/lib/events/event.cpp b/lib/events/event.cpp
index 4c304a3c..1f1eebaa 100644
--- a/lib/events/event.cpp
+++ b/lib/events/event.cpp
@@ -29,7 +29,7 @@ Event::Event(Type type, const QJsonObject& json) : _type(type), _json(json)
 }
 
 Event::Event(Type type, event_mtype_t matrixType, const QJsonObject& contentJson)
-    : Event(type, basicEventJson(matrixType, contentJson))
+    : Event(type, basicJson(matrixType, contentJson))
 {}
 
 Event::~Event() = default;
diff --git a/lib/events/event.h b/lib/events/event.h
index 113fa3fa..ec21c6aa 100644
--- a/lib/events/event.h
+++ b/lib/events/event.h
@@ -48,13 +48,6 @@ const QString RoomIdKey { RoomIdKeyL };
 const QString UnsignedKey { UnsignedKeyL };
 const QString StateKeyKey { StateKeyKeyL };
 
-/// Make a minimal correct Matrix event JSON
-inline QJsonObject basicEventJson(const QString& matrixType,
-                                  const QJsonObject& content)
-{
-    return { { TypeKey, matrixType }, { ContentKey, content } };
-}
-
 // === Event types ===
 
 using event_type_t = QLatin1String;
@@ -193,6 +186,13 @@ public:
     Event& operator=(Event&&) = delete;
     virtual ~Event();
 
+    /// Make a minimal correct Matrix event JSON
+    static QJsonObject basicJson(const QString& matrixType,
+                                 const QJsonObject& content)
+    {
+        return { { TypeKey, matrixType }, { ContentKey, content } };
+    }
+
     Type type() const { return _type; }
     QString matrixType() const;
     [[deprecated("Use fullJson() and stringify it with QJsonDocument::toJson() "
@@ -258,6 +258,21 @@ template <typename EventT>
 using EventsArray = std::vector<event_ptr_tt<EventT>>;
 using Events = EventsArray<Event>;
 
+//! \brief Define an inline method obtaining a content part
+//!
+//! This macro adds a const method that extracts a JSON value at the key
+//! <tt>toSnakeCase(PartName_)</tt> (sic) and converts it to the type
+//! \p PartType_. Effectively, the generated method is an equivalent of
+//! \code
+//! contentPart<PartType_>(Quotient::toSnakeCase(#PartName_##_ls));
+//! \endcode
+#define QUO_CONTENT_GETTER(PartType_, PartName_)                  \
+    PartType_ PartName_() const                                   \
+    {                                                             \
+        static const auto JsonKey = toSnakeCase(#PartName_##_ls); \
+        return contentPart<PartType_>(JsonKey);                   \
+    }
+
 // === Facilities for event class definitions ===
 
 // This macro should be used in a public section of an event class to
@@ -278,6 +293,32 @@ using Events = EventsArray<Event>;
         Type_::factory.addMethod<Type_>();                        \
     // End of macro
 
+/// \brief Define a new event class with a single key-value pair in the content
+///
+/// This macro defines a new event class \p Name_ derived from \p Base_,
+/// with Matrix event type \p TypeId_, providing a getter named \p GetterName_
+/// for a single value of type \p ValueType_ inside the event content.
+/// To retrieve the value the getter uses a JSON key name that corresponds to
+/// its own (getter's) name but written in snake_case. \p GetterName_ must be
+/// in camelCase, no quotes (an identifier, not a literal).
+#define DEFINE_SIMPLE_EVENT(Name_, Base_, TypeId_, ValueType_, GetterName_)     \
+    class QUOTIENT_API Name_ : public Base_ {                                   \
+    public:                                                                     \
+        using content_type = ValueType_;                                        \
+        DEFINE_EVENT_TYPEID(TypeId_, Name_)                                     \
+        explicit Name_(const QJsonObject& obj) : Base_(TypeId, obj) {}          \
+        explicit Name_(const content_type& content)                             \
+            : Name_(Base_::basicJson(TypeId, { { JsonKey, toJson(content) } })) \
+        {}                                                                      \
+        auto GetterName_() const                                                \
+        {                                                                       \
+            return contentPart<content_type>(JsonKey);                          \
+        }                                                                       \
+        static inline const auto JsonKey = toSnakeCase(#GetterName_##_ls);      \
+    };                                                                          \
+    REGISTER_EVENT_TYPE(Name_)                                                  \
+    // End of macro
+
 // === is<>(), eventCast<>() and switchOnType<>() ===
 
 template <class EventT>
diff --git a/lib/events/eventcontent.cpp b/lib/events/eventcontent.cpp
index 9d7edf20..6218e3b8 100644
--- a/lib/events/eventcontent.cpp
+++ b/lib/events/eventcontent.cpp
@@ -15,7 +15,7 @@ using std::move;
 QJsonObject Base::toJson() const
 {
     QJsonObject o;
-    fillJson(&o);
+    fillJson(o);
     return o;
 }
 
@@ -29,12 +29,13 @@ FileInfo::FileInfo(const QFileInfo &fi)
 }
 
 FileInfo::FileInfo(QUrl u, qint64 payloadSize, const QMimeType& mimeType,
-                   Omittable<EncryptedFile> file, QString originalFilename)
+                   Omittable<EncryptedFile> encryptedFile,
+                   QString originalFilename)
     : mimeType(mimeType)
     , url(move(u))
     , payloadSize(payloadSize)
     , originalName(move(originalFilename))
-    , file(file)
+    , file(move(encryptedFile))
 {
     if (!isValid())
         qCWarning(MESSAGES)
@@ -44,7 +45,7 @@ FileInfo::FileInfo(QUrl u, qint64 payloadSize, const QMimeType& mimeType,
 }
 
 FileInfo::FileInfo(QUrl mxcUrl, const QJsonObject& infoJson,
-                   const Omittable<EncryptedFile> &file,
+                   Omittable<EncryptedFile> encryptedFile,
                    QString originalFilename)
     : originalInfoJson(infoJson)
     , mimeType(
@@ -52,7 +53,7 @@ FileInfo::FileInfo(QUrl mxcUrl, const QJsonObject& infoJson,
     , url(move(mxcUrl))
     , payloadSize(fromJson<qint64>(infoJson["size"_ls]))
     , originalName(move(originalFilename))
-    , file(file)
+    , file(move(encryptedFile))
 {
     if(url.isEmpty() && file.has_value()) {
         url = file->url;
@@ -67,14 +68,15 @@ bool FileInfo::isValid() const
            && (url.authority() + url.path()).count('/') == 1;
 }
 
-void FileInfo::fillInfoJson(QJsonObject* infoJson) const
+QJsonObject Quotient::EventContent::toInfoJson(const FileInfo& info)
 {
-    Q_ASSERT(infoJson);
-    if (payloadSize != -1)
-        infoJson->insert(QStringLiteral("size"), payloadSize);
-    if (mimeType.isValid())
-        infoJson->insert(QStringLiteral("mimetype"), mimeType.name());
+    QJsonObject infoJson;
+    if (info.payloadSize != -1)
+        infoJson.insert(QStringLiteral("size"), info.payloadSize);
+    if (info.mimeType.isValid())
+        infoJson.insert(QStringLiteral("mimetype"), info.mimeType.name());
     //TODO add encryptedfile
+    return infoJson;
 }
 
 ImageInfo::ImageInfo(const QFileInfo& fi, QSize imageSize)
@@ -82,38 +84,40 @@ ImageInfo::ImageInfo(const QFileInfo& fi, QSize imageSize)
 {}
 
 ImageInfo::ImageInfo(const QUrl& mxcUrl, qint64 fileSize, const QMimeType& type,
-                     QSize imageSize, const Omittable<EncryptedFile> &file, const QString& originalFilename)
-    : FileInfo(mxcUrl, fileSize, type, file, originalFilename)
+                     QSize imageSize, Omittable<EncryptedFile> encryptedFile,
+                     const QString& originalFilename)
+    : FileInfo(mxcUrl, fileSize, type, move(encryptedFile), originalFilename)
     , imageSize(imageSize)
 {}
 
 ImageInfo::ImageInfo(const QUrl& mxcUrl, const QJsonObject& infoJson,
-                     const Omittable<EncryptedFile> &file,
+                     Omittable<EncryptedFile> encryptedFile,
                      const QString& originalFilename)
-    : FileInfo(mxcUrl, infoJson, file, originalFilename)
+    : FileInfo(mxcUrl, infoJson, move(encryptedFile), originalFilename)
     , imageSize(infoJson["w"_ls].toInt(), infoJson["h"_ls].toInt())
 {}
 
-void ImageInfo::fillInfoJson(QJsonObject* infoJson) const
+QJsonObject Quotient::EventContent::toInfoJson(const ImageInfo& info)
 {
-    FileInfo::fillInfoJson(infoJson);
-    if (imageSize.width() != -1)
-        infoJson->insert(QStringLiteral("w"), imageSize.width());
-    if (imageSize.height() != -1)
-        infoJson->insert(QStringLiteral("h"), imageSize.height());
+    auto infoJson = toInfoJson(static_cast<const FileInfo&>(info));
+    if (info.imageSize.width() != -1)
+        infoJson.insert(QStringLiteral("w"), info.imageSize.width());
+    if (info.imageSize.height() != -1)
+        infoJson.insert(QStringLiteral("h"), info.imageSize.height());
+    return infoJson;
 }
 
-Thumbnail::Thumbnail(const QJsonObject& infoJson, const Omittable<EncryptedFile> &file)
+Thumbnail::Thumbnail(const QJsonObject& infoJson,
+                     Omittable<EncryptedFile> encryptedFile)
     : ImageInfo(QUrl(infoJson["thumbnail_url"_ls].toString()),
-                infoJson["thumbnail_info"_ls].toObject(),
-                file)
+                infoJson["thumbnail_info"_ls].toObject(), move(encryptedFile))
 {}
 
-void Thumbnail::fillInfoJson(QJsonObject* infoJson) const
+void Thumbnail::dumpTo(QJsonObject& infoJson) const
 {
     if (url.isValid())
-        infoJson->insert(QStringLiteral("thumbnail_url"), url.toString());
+        infoJson.insert(QStringLiteral("thumbnail_url"), url.toString());
     if (!imageSize.isEmpty())
-        infoJson->insert(QStringLiteral("thumbnail_info"),
-                         toInfoJson<ImageInfo>(*this));
+        infoJson.insert(QStringLiteral("thumbnail_info"),
+                         toInfoJson(*this));
 }
diff --git a/lib/events/eventcontent.h b/lib/events/eventcontent.h
index de9a792b..bbd35618 100644
--- a/lib/events/eventcontent.h
+++ b/lib/events/eventcontent.h
@@ -19,22 +19,18 @@ class QFileInfo;
 
 namespace Quotient {
 namespace EventContent {
-    /**
-     * A base class for all content types that can be stored
-     * in a RoomMessageEvent
-     *
-     * Each content type class should have a constructor taking
-     * a QJsonObject and override fillJson() with an implementation
-     * that will fill the target QJsonObject with stored values. It is
-     * assumed but not required that a content object can also be created
-     * from plain data.
-     */
+    //! \brief Base for all content types that can be stored in RoomMessageEvent
+    //!
+    //! Each content type class should have a constructor taking
+    //! a QJsonObject and override fillJson() with an implementation
+    //! that will fill the target QJsonObject with stored values. It is
+    //! assumed but not required that a content object can also be created
+    //! from plain data.
     class QUOTIENT_API Base {
     public:
         explicit Base(QJsonObject o = {}) : originalJson(std::move(o)) {}
         virtual ~Base() = default;
 
-        // FIXME: make toJson() from converters.* work on base classes
         QJsonObject toJson() const;
 
     public:
@@ -44,7 +40,7 @@ namespace EventContent {
         Base(const Base&) = default;
         Base(Base&&) = default;
 
-        virtual void fillJson(QJsonObject* o) const = 0;
+        virtual void fillJson(QJsonObject&) const = 0;
     };
 
     // The below structures fairly follow CS spec 11.2.1.6. The overall
@@ -54,52 +50,64 @@ namespace EventContent {
 
     // A quick classes inheritance structure follows (the definitions are
     // spread across eventcontent.h and roommessageevent.h):
+    // UrlBasedContent<InfoT> : InfoT + url and thumbnail data
+    //   PlayableContent<InfoT> : + duration attribute
     // FileInfo
-    //   FileContent : UrlWithThumbnailContent<FileInfo>
-    //   AudioContent : PlayableContent<UrlBasedContent<FileInfo>>
+    //   FileContent = UrlBasedContent<FileInfo>
+    //   AudioContent = PlayableContent<FileInfo>
     //   ImageInfo : FileInfo + imageSize attribute
-    //     ImageContent : UrlWithThumbnailContent<ImageInfo>
-    //     VideoContent : PlayableContent<UrlWithThumbnailContent<ImageInfo>>
-
-    /**
-     * A base/mixin class for structures representing an "info" object for
-     * some content types. These include most attachment types currently in
-     * the CS API spec.
-     *
-     * In order to use it in a content class, derive both from TypedBase
-     * (or Base) and from FileInfo (or its derivative, such as \p ImageInfo)
-     * and call fillInfoJson() to fill the "info" subobject. Make sure
-     * to pass an "info" part of JSON to FileInfo constructor, not the whole
-     * JSON content, as well as contents of "url" (or a similar key) and
-     * optionally "filename" node from the main JSON content. Assuming you
-     * don't do unusual things, you should use \p UrlBasedContent<> instead
-     * of doing multiple inheritance and overriding Base::fillJson() by hand.
-     *
-     * This class is not polymorphic.
-     */
+    //     ImageContent = UrlBasedContent<ImageInfo>
+    //     VideoContent = PlayableContent<ImageInfo>
+
+    //! \brief Mix-in class representing `info` subobject in content JSON
+    //!
+    //! This is one of base classes for content types that deal with files or
+    //! URLs. It stores the file metadata attributes, such as size, MIME type
+    //! etc. found in the `content/info` subobject of event JSON payloads.
+    //! Actual content classes derive from this class _and_ TypedBase that
+    //! provides a polymorphic interface to access data in the mix-in. FileInfo
+    //! (as well as ImageInfo, that adds image size to the metadata) is NOT
+    //! polymorphic and is used in a non-polymorphic way to store thumbnail
+    //! metadata (in a separate instance), next to the metadata on the file
+    //! itself.
+    //!
+    //! If you need to make a new _content_ (not info) class based on files/URLs
+    //! take UrlBasedContent as the example, i.e.:
+    //! 1. Double-inherit from this class (or ImageInfo) and TypedBase.
+    //! 2. Provide a constructor from QJsonObject that will pass the `info`
+    //!    subobject (not the whole content JSON) down to FileInfo/ImageInfo.
+    //! 3. Override fillJson() to customise the JSON export logic. Make sure
+    //!    to call toInfoJson() from it to produce the payload for the `info`
+    //!    subobject in the JSON payload.
+    //!
+    //! \sa ImageInfo, FileContent, ImageContent, AudioContent, VideoContent,
+    //!     UrlBasedContent
     class QUOTIENT_API FileInfo {
     public:
         FileInfo() = default;
+        //! \brief Construct from a QFileInfo object
+        //!
+        //! \param fi a QFileInfo object referring to an existing file
         explicit FileInfo(const QFileInfo& fi);
         explicit FileInfo(QUrl mxcUrl, qint64 payloadSize = -1,
                           const QMimeType& mimeType = {},
-                          Omittable<EncryptedFile> file = none,
+                          Omittable<EncryptedFile> encryptedFile = none,
                           QString originalFilename = {});
+        //! \brief Construct from a JSON `info` payload
+        //!
+        //! Make sure to pass the `info` subobject of content JSON, not the
+        //! whole JSON content.
         FileInfo(QUrl mxcUrl, const QJsonObject& infoJson,
-                 const Omittable<EncryptedFile> &file,
+                 Omittable<EncryptedFile> encryptedFile,
                  QString originalFilename = {});
 
         bool isValid() const;
 
-        void fillInfoJson(QJsonObject* infoJson) const;
-
-        /**
-         * \brief Extract media id from the URL
-         *
-         * This can be used, e.g., to construct a QML-facing image://
-         * URI as follows:
-         * \code "image://provider/" + info.mediaId() \endcode
-         */
+        //! \brief Extract media id from the URL
+        //!
+        //! This can be used, e.g., to construct a QML-facing image://
+        //! URI as follows:
+        //! \code "image://provider/" + info.mediaId() \endcode
         QString mediaId() const { return url.authority() + url.path(); }
 
     public:
@@ -111,52 +119,40 @@ namespace EventContent {
         Omittable<EncryptedFile> file = none;
     };
 
-    template <typename InfoT>
-    QJsonObject toInfoJson(const InfoT& info)
-    {
-        QJsonObject infoJson;
-        info.fillInfoJson(&infoJson);
-        return infoJson;
-    }
+    QUOTIENT_API QJsonObject toInfoJson(const FileInfo& info);
 
-    /**
-     * A content info class for image content types: image, thumbnail, video
-     */
+    //! \brief A content info class for image/video content types and thumbnails
     class QUOTIENT_API ImageInfo : public FileInfo {
     public:
         ImageInfo() = default;
         explicit ImageInfo(const QFileInfo& fi, QSize imageSize = {});
         explicit ImageInfo(const QUrl& mxcUrl, qint64 fileSize = -1,
                            const QMimeType& type = {}, QSize imageSize = {},
-                           const Omittable<EncryptedFile> &file = none,
+                           Omittable<EncryptedFile> encryptedFile = none,
                            const QString& originalFilename = {});
         ImageInfo(const QUrl& mxcUrl, const QJsonObject& infoJson,
-                  const Omittable<EncryptedFile> &encryptedFile,
+                  Omittable<EncryptedFile> encryptedFile,
                   const QString& originalFilename = {});
 
-        void fillInfoJson(QJsonObject* infoJson) const;
-
     public:
         QSize imageSize;
     };
 
-    /**
-     * An auxiliary class for an info type that carries a thumbnail
-     *
-     * This class saves/loads a thumbnail to/from "info" subobject of
-     * the JSON representation of event content; namely,
-     * "info/thumbnail_url" and "info/thumbnail_info" fields are used.
-     */
+    QUOTIENT_API QJsonObject toInfoJson(const ImageInfo& info);
+
+    //! \brief An auxiliary class for an info type that carries a thumbnail
+    //!
+    //! This class saves/loads a thumbnail to/from `info` subobject of
+    //! the JSON representation of event content; namely, `info/thumbnail_url`
+    //! and `info/thumbnail_info` fields are used.
     class QUOTIENT_API Thumbnail : public ImageInfo {
     public:
         using ImageInfo::ImageInfo;
-        Thumbnail(const QJsonObject& infoJson, const Omittable<EncryptedFile> &file = none);
+        Thumbnail(const QJsonObject& infoJson,
+                  Omittable<EncryptedFile> encryptedFile = none);
 
-        /**
-         * Writes thumbnail information to "thumbnail_info" subobject
-         * and thumbnail URL to "thumbnail_url" node inside "info".
-         */
-        void fillInfoJson(QJsonObject* infoJson) const;
+        //! \brief Add thumbnail information to the passed `info` JSON object
+        void dumpTo(QJsonObject& infoJson) const;
     };
 
     class QUOTIENT_API TypedBase : public Base {
@@ -171,114 +167,91 @@ namespace EventContent {
         using Base::Base;
     };
 
-    /**
-     * A base class for content types that have a URL and additional info
-     *
-     * Types that derive from this class template take "url" and,
-     * optionally, "filename" values from the top-level JSON object and
-     * the rest of information from the "info" subobject, as defined by
-     * the parameter type.
-     *
-     * \tparam InfoT base info class
-     */
+    //! \brief A template class for content types with a URL and additional info
+    //!
+    //! Types that derive from this class template take `url` and,
+    //! optionally, `filename` values from the top-level JSON object and
+    //! the rest of information from the `info` subobject, as defined by
+    //! the parameter type.
+    //! \tparam InfoT base info class - FileInfo or ImageInfo
     template <class InfoT>
-    class QUOTIENT_API UrlBasedContent : public TypedBase, public InfoT {
+    class UrlBasedContent : public TypedBase, public InfoT {
     public:
         using InfoT::InfoT;
         explicit UrlBasedContent(const QJsonObject& json)
             : TypedBase(json)
             , InfoT(QUrl(json["url"].toString()), json["info"].toObject(),
-                    fromJson<Omittable<EncryptedFile>>(json["file"]), json["filename"].toString())
+                    fromJson<Omittable<EncryptedFile>>(json["file"]),
+                    json["filename"].toString())
+            , thumbnail(FileInfo::originalInfoJson)
         {
-            // A small hack to facilitate links creation in QML.
+            // Two small hacks on originalJson to expose mediaIds to QML
             originalJson.insert("mediaId", InfoT::mediaId());
+            originalJson.insert("thumbnailMediaId", thumbnail.mediaId());
         }
 
         QMimeType type() const override { return InfoT::mimeType; }
         const FileInfo* fileInfo() const override { return this; }
         FileInfo* fileInfo() override { return this; }
-
-    protected:
-        void fillJson(QJsonObject* json) const override
-        {
-            Q_ASSERT(json);
-            if (!InfoT::file.has_value()) {
-                json->insert("url", InfoT::url.toString());
-            } else {
-                json->insert("file", Quotient::toJson(*InfoT::file));
-            }
-            if (!InfoT::originalName.isEmpty())
-                json->insert("filename", InfoT::originalName);
-            json->insert("info", toInfoJson<InfoT>(*this));
-        }
-    };
-
-    template <typename InfoT>
-    class QUOTIENT_API UrlWithThumbnailContent : public UrlBasedContent<InfoT> {
-    public:
-        // NB: when using inherited constructors, thumbnail has to be
-        // initialised separately
-        using UrlBasedContent<InfoT>::UrlBasedContent;
-        explicit UrlWithThumbnailContent(const QJsonObject& json)
-            : UrlBasedContent<InfoT>(json), thumbnail(InfoT::originalInfoJson)
-        {
-            // Another small hack, to simplify making a thumbnail link
-            UrlBasedContent<InfoT>::originalJson.insert("thumbnailMediaId",
-                                                        thumbnail.mediaId());
-        }
-
         const Thumbnail* thumbnailInfo() const override { return &thumbnail; }
 
     public:
         Thumbnail thumbnail;
 
     protected:
-        void fillJson(QJsonObject* json) const override
+        virtual void fillInfoJson(QJsonObject& infoJson [[maybe_unused]]) const
+        {}
+
+        void fillJson(QJsonObject& json) const override
         {
-            UrlBasedContent<InfoT>::fillJson(json);
-            auto infoJson = json->take("info").toObject();
-            thumbnail.fillInfoJson(&infoJson);
-            json->insert("info", infoJson);
+            if (!InfoT::file.has_value()) {
+                json.insert("url", InfoT::url.toString());
+            } else {
+                json.insert("file", Quotient::toJson(*InfoT::file));
+            }
+            if (!InfoT::originalName.isEmpty())
+                json.insert("filename", InfoT::originalName);
+            auto infoJson = toInfoJson(*this);
+            if (thumbnail.isValid())
+                thumbnail.dumpTo(infoJson);
+            fillInfoJson(infoJson);
+            json.insert("info", infoJson);
         }
     };
 
-    /**
-     * Content class for m.image
-     *
-     * Available fields:
-     * - corresponding to the top-level JSON:
-     *   - url
-     *   - filename (extension to the spec)
-     * - corresponding to the "info" subobject:
-     *   - payloadSize ("size" in JSON)
-     *   - mimeType ("mimetype" in JSON)
-     *   - imageSize (QSize for a combination of "h" and "w" in JSON)
-     *   - thumbnail.url ("thumbnail_url" in JSON)
-     * - corresponding to the "info/thumbnail_info" subobject: contents of
-     *   thumbnail field, in the same vein as for the main image:
-     *   - payloadSize
-     *   - mimeType
-     *   - imageSize
-     */
-    using ImageContent = UrlWithThumbnailContent<ImageInfo>;
-
-    /**
-     * Content class for m.file
-     *
-     * Available fields:
-     * - corresponding to the top-level JSON:
-     *   - url
-     *   - filename
-     * - corresponding to the "info" subobject:
-     *   - payloadSize ("size" in JSON)
-     *   - mimeType ("mimetype" in JSON)
-     *   - thumbnail.url ("thumbnail_url" in JSON)
-     * - corresponding to the "info/thumbnail_info" subobject:
-     *   - thumbnail.payloadSize
-     *   - thumbnail.mimeType
-     *   - thumbnail.imageSize (QSize for "h" and "w" in JSON)
-     */
-    using FileContent = UrlWithThumbnailContent<FileInfo>;
+    //! \brief Content class for m.image
+    //!
+    //! Available fields:
+    //! - corresponding to the top-level JSON:
+    //!   - url
+    //!   - filename (extension to the spec)
+    //! - corresponding to the `info` subobject:
+    //!   - payloadSize (`size` in JSON)
+    //!   - mimeType (`mimetype` in JSON)
+    //!   - imageSize (QSize for a combination of `h` and `w` in JSON)
+    //!   - thumbnail.url (`thumbnail_url` in JSON)
+    //! - corresponding to the `info/thumbnail_info` subobject: contents of
+    //!   thumbnail field, in the same vein as for the main image:
+    //!   - payloadSize
+    //!   - mimeType
+    //!   - imageSize
+    using ImageContent = UrlBasedContent<ImageInfo>;
+
+    //! \brief Content class for m.file
+    //!
+    //! Available fields:
+    //! - corresponding to the top-level JSON:
+    //!   - url
+    //!   - filename
+    //! - corresponding to the `info` subobject:
+    //!   - payloadSize (`size` in JSON)
+    //!   - mimeType (`mimetype` in JSON)
+    //!   - thumbnail.url (`thumbnail_url` in JSON)
+    //! - corresponding to the `info/thumbnail_info` subobject:
+    //!   - thumbnail.payloadSize
+    //!   - thumbnail.mimeType
+    //!   - thumbnail.imageSize (QSize for `h` and `w` in JSON)
+    using FileContent = UrlBasedContent<FileInfo>;
 } // namespace EventContent
 } // namespace Quotient
 Q_DECLARE_METATYPE(const Quotient::EventContent::TypedBase*)
diff --git a/lib/events/eventloader.h b/lib/events/eventloader.h
index fe624d70..c7b82e8e 100644
--- a/lib/events/eventloader.h
+++ b/lib/events/eventloader.h
@@ -29,7 +29,7 @@ template <typename BaseEventT>
 inline event_ptr_tt<BaseEventT> loadEvent(const QString& matrixType,
                                           const QJsonObject& content)
 {
-    return doLoadEvent<BaseEventT>(basicEventJson(matrixType, content),
+    return doLoadEvent<BaseEventT>(Event::basicJson(matrixType, content),
                                    matrixType);
 }
 
@@ -44,7 +44,7 @@ inline StateEventPtr loadStateEvent(const QString& matrixType,
                                     const QString& stateKey = {})
 {
     return doLoadEvent<StateEventBase>(
-        basicStateEventJson(matrixType, content, stateKey), matrixType);
+        StateEventBase::basicJson(matrixType, content, stateKey), matrixType);
 }
 
 template <typename EventT>
diff --git a/lib/events/redactionevent.h b/lib/events/redactionevent.h
index be20bf52..1c486a44 100644
--- a/lib/events/redactionevent.h
+++ b/lib/events/redactionevent.h
@@ -17,7 +17,7 @@ public:
     {
         return fullJson()["redacts"_ls].toString();
     }
-    QString reason() const { return contentPart<QString>("reason"_ls); }
+    QUO_CONTENT_GETTER(QString, reason)
 };
 REGISTER_EVENT_TYPE(RedactionEvent)
 } // namespace Quotient
diff --git a/lib/events/roomevent.cpp b/lib/events/roomevent.cpp
index 2f482871..3ddf5ac4 100644
--- a/lib/events/roomevent.cpp
+++ b/lib/events/roomevent.cpp
@@ -101,22 +101,22 @@ void RoomEvent::dumpTo(QDebug dbg) const
     dbg << " (made at " << originTimestamp().toString(Qt::ISODate) << ')';
 }
 
-QJsonObject makeCallContentJson(const QString& callId, int version,
-                                QJsonObject content)
+QJsonObject CallEventBase::basicJson(const QString& matrixType,
+                                     const QString& callId, int version,
+                                     QJsonObject contentJson)
 {
-    content.insert(QStringLiteral("call_id"), callId);
-    content.insert(QStringLiteral("version"), version);
-    return content;
+    contentJson.insert(QStringLiteral("call_id"), callId);
+    contentJson.insert(QStringLiteral("version"), version);
+    return RoomEvent::basicJson(matrixType, contentJson);
 }
 
 CallEventBase::CallEventBase(Type type, event_mtype_t matrixType,
                              const QString& callId, int version,
                              const QJsonObject& contentJson)
-    : RoomEvent(type, matrixType,
-                makeCallContentJson(callId, version, contentJson))
+    : RoomEvent(type, basicJson(matrixType, callId, version, contentJson))
 {}
 
-CallEventBase::CallEventBase(Event::Type type, const QJsonObject& json)
+CallEventBase::CallEventBase(Type type, const QJsonObject& json)
     : RoomEvent(type, json)
 {
     if (callId().isEmpty())
diff --git a/lib/events/roomevent.h b/lib/events/roomevent.h
index a7d6c428..7f724689 100644
--- a/lib/events/roomevent.h
+++ b/lib/events/roomevent.h
@@ -96,8 +96,13 @@ public:
     ~CallEventBase() override = default;
     bool isCallEvent() const override { return true; }
 
-    QString callId() const { return contentPart<QString>("call_id"_ls); }
-    int version() const { return contentPart<int>("version"_ls); }
+    QUO_CONTENT_GETTER(QString, callId)
+    QUO_CONTENT_GETTER(int, version)
+
+protected:
+    static QJsonObject basicJson(const QString& matrixType,
+                                 const QString& callId, int version,
+                                 QJsonObject contentJson = {});
 };
 } // namespace Quotient
 Q_DECLARE_METATYPE(Quotient::RoomEvent*)
diff --git a/lib/events/roommemberevent.cpp b/lib/events/roommemberevent.cpp
index b4770224..c3be0e00 100644
--- a/lib/events/roommemberevent.cpp
+++ b/lib/events/roommemberevent.cpp
@@ -4,8 +4,6 @@
 
 #include "roommemberevent.h"
 
-#include "logging.h"
-
 #include <QtCore/QtAlgorithms>
 
 namespace Quotient {
@@ -43,19 +41,20 @@ MemberEventContent::MemberEventContent(const QJsonObject& json)
         displayName = sanitized(*displayName);
 }
 
-void MemberEventContent::fillJson(QJsonObject* o) const
+QJsonObject MemberEventContent::toJson() const
 {
-    Q_ASSERT(o);
+    QJsonObject o;
     if (membership != Membership::Invalid)
-        o->insert(QStringLiteral("membership"),
+        o.insert(QStringLiteral("membership"),
                   MembershipStrings[qCountTrailingZeroBits(
                       std::underlying_type_t<Membership>(membership))]);
     if (displayName)
-        o->insert(QStringLiteral("displayname"), *displayName);
+        o.insert(QStringLiteral("displayname"), *displayName);
     if (avatarUrl && avatarUrl->isValid())
-        o->insert(QStringLiteral("avatar_url"), avatarUrl->toString());
+        o.insert(QStringLiteral("avatar_url"), avatarUrl->toString());
     if (!reason.isEmpty())
-        o->insert(QStringLiteral("reason"), reason);
+        o.insert(QStringLiteral("reason"), reason);
+    return o;
 }
 
 bool RoomMemberEvent::changesMembership() const
diff --git a/lib/events/roommemberevent.h b/lib/events/roommemberevent.h
index ceb7826b..dd33ea6b 100644
--- a/lib/events/roommemberevent.h
+++ b/lib/events/roommemberevent.h
@@ -5,18 +5,18 @@
 
 #pragma once
 
-#include "eventcontent.h"
 #include "stateevent.h"
 #include "quotient_common.h"
 
 namespace Quotient {
-class QUOTIENT_API MemberEventContent : public EventContent::Base {
+class QUOTIENT_API MemberEventContent {
 public:
     using MembershipType
         [[deprecated("Use Quotient::Membership instead")]] = Membership;
 
     QUO_IMPLICIT MemberEventContent(Membership ms) : membership(ms) {}
     explicit MemberEventContent(const QJsonObject& json);
+    QJsonObject toJson() const;
 
     Membership membership;
     /// (Only for invites) Whether the invite is to a direct chat
@@ -24,9 +24,6 @@ public:
     Omittable<QString> displayName;
     Omittable<QUrl> avatarUrl;
     QString reason;
-
-protected:
-    void fillJson(QJsonObject* o) const override;
 };
 
 using MembershipType [[deprecated("Use Membership instead")]] = Membership;
diff --git a/lib/events/roommessageevent.cpp b/lib/events/roommessageevent.cpp
index d63352cb..d9d3fbe0 100644
--- a/lib/events/roommessageevent.cpp
+++ b/lib/events/roommessageevent.cpp
@@ -302,17 +302,16 @@ TextContent::TextContent(const QJsonObject& json)
     }
 }
 
-void TextContent::fillJson(QJsonObject* json) const
+void TextContent::fillJson(QJsonObject &json) const
 {
     static const auto FormatKey = QStringLiteral("format");
 
-    Q_ASSERT(json);
     if (mimeType.inherits("text/html")) {
-        json->insert(FormatKey, HtmlContentTypeId);
-        json->insert(FormattedBodyKey, body);
+        json.insert(FormatKey, HtmlContentTypeId);
+        json.insert(FormattedBodyKey, body);
     }
     if (relatesTo) {
-        json->insert(
+        json.insert(
             QStringLiteral("m.relates_to"),
             relatesTo->type == EventRelation::ReplyType
                 ? QJsonObject { { relatesTo->type,
@@ -326,7 +325,7 @@ void TextContent::fillJson(QJsonObject* json) const
                 newContentJson.insert(FormatKey, HtmlContentTypeId);
                 newContentJson.insert(FormattedBodyKey, body);
             }
-            json->insert(QStringLiteral("m.new_content"), newContentJson);
+            json.insert(QStringLiteral("m.new_content"), newContentJson);
         }
     }
 }
@@ -347,9 +346,8 @@ QMimeType LocationContent::type() const
     return QMimeDatabase().mimeTypeForData(geoUri.toLatin1());
 }
 
-void LocationContent::fillJson(QJsonObject* o) const
+void LocationContent::fillJson(QJsonObject& o) const
 {
-    Q_ASSERT(o);
-    o->insert(QStringLiteral("geo_uri"), geoUri);
-    o->insert(QStringLiteral("info"), toInfoJson(thumbnail));
+    o.insert(QStringLiteral("geo_uri"), geoUri);
+    o.insert(QStringLiteral("info"), toInfoJson(thumbnail));
 }
diff --git a/lib/events/roommessageevent.h b/lib/events/roommessageevent.h
index 03a51328..6968ad70 100644
--- a/lib/events/roommessageevent.h
+++ b/lib/events/roommessageevent.h
@@ -136,7 +136,7 @@ namespace EventContent {
         Omittable<EventRelation> relatesTo;
 
     protected:
-        void fillJson(QJsonObject* json) const override;
+        void fillJson(QJsonObject& json) const override;
     };
 
     /**
@@ -164,28 +164,25 @@ namespace EventContent {
         Thumbnail thumbnail;
 
     protected:
-        void fillJson(QJsonObject* o) const override;
+        void fillJson(QJsonObject& o) const override;
     };
 
     /**
      * A base class for info types that include duration: audio and video
      */
-    template <typename ContentT>
-    class QUOTIENT_API PlayableContent : public ContentT {
+    template <typename InfoT>
+    class PlayableContent : public UrlBasedContent<InfoT> {
     public:
-        using ContentT::ContentT;
+        using UrlBasedContent<InfoT>::UrlBasedContent;
         PlayableContent(const QJsonObject& json)
-            : ContentT(json)
-            , duration(ContentT::originalInfoJson["duration"_ls].toInt())
+            : UrlBasedContent<InfoT>(json)
+            , duration(FileInfo::originalInfoJson["duration"_ls].toInt())
         {}
 
     protected:
-        void fillJson(QJsonObject* json) const override
+        void fillInfoJson(QJsonObject& infoJson) const override
         {
-            ContentT::fillJson(json);
-            auto infoJson = json->take("info"_ls).toObject();
             infoJson.insert(QStringLiteral("duration"), duration);
-            json->insert(QStringLiteral("info"), infoJson);
         }
 
     public:
@@ -211,7 +208,7 @@ namespace EventContent {
      *   - mimeType
      *   - imageSize
      */
-    using VideoContent = PlayableContent<UrlWithThumbnailContent<ImageInfo>>;
+    using VideoContent = PlayableContent<ImageInfo>;
 
     /**
      * Content class for m.audio
@@ -224,7 +221,13 @@ namespace EventContent {
      *   - payloadSize ("size" in JSON)
      *   - mimeType ("mimetype" in JSON)
      *   - duration
+     *   - thumbnail.url ("thumbnail_url" in JSON - extension to the spec)
+     * - corresponding to the "info/thumbnail_info" subobject: contents of
+     *   thumbnail field (extension to the spec):
+     *   - payloadSize
+     *   - mimeType
+     *   - imageSize
      */
-    using AudioContent = PlayableContent<UrlBasedContent<FileInfo>>;
+    using AudioContent = PlayableContent<FileInfo>;
 } // namespace EventContent
 } // namespace Quotient
diff --git a/lib/events/roompowerlevelsevent.cpp b/lib/events/roompowerlevelsevent.cpp
index 8d262ddf..84a31d55 100644
--- a/lib/events/roompowerlevelsevent.cpp
+++ b/lib/events/roompowerlevelsevent.cpp
@@ -3,8 +3,6 @@
 
 #include "roompowerlevelsevent.h"
 
-#include <QJsonDocument>
-
 using namespace Quotient;
 
 PowerLevelsEventContent::PowerLevelsEventContent(const QJsonObject& json) :
@@ -21,17 +19,21 @@ PowerLevelsEventContent::PowerLevelsEventContent(const QJsonObject& json) :
 {
 }
 
-void PowerLevelsEventContent::fillJson(QJsonObject* o) const {
-    o->insert(QStringLiteral("invite"), invite);
-    o->insert(QStringLiteral("kick"), kick);
-    o->insert(QStringLiteral("ban"), ban);
-    o->insert(QStringLiteral("redact"), redact);
-    o->insert(QStringLiteral("events"), Quotient::toJson(events));
-    o->insert(QStringLiteral("events_default"), eventsDefault);
-    o->insert(QStringLiteral("state_default"), stateDefault);
-    o->insert(QStringLiteral("users"), Quotient::toJson(users));
-    o->insert(QStringLiteral("users_default"), usersDefault);
-    o->insert(QStringLiteral("notifications"), QJsonObject{{"room", notifications.room}});
+QJsonObject PowerLevelsEventContent::toJson() const
+{
+    QJsonObject o;
+    o.insert(QStringLiteral("invite"), invite);
+    o.insert(QStringLiteral("kick"), kick);
+    o.insert(QStringLiteral("ban"), ban);
+    o.insert(QStringLiteral("redact"), redact);
+    o.insert(QStringLiteral("events"), Quotient::toJson(events));
+    o.insert(QStringLiteral("events_default"), eventsDefault);
+    o.insert(QStringLiteral("state_default"), stateDefault);
+    o.insert(QStringLiteral("users"), Quotient::toJson(users));
+    o.insert(QStringLiteral("users_default"), usersDefault);
+    o.insert(QStringLiteral("notifications"),
+             QJsonObject { { "room", notifications.room } });
+    return o;
 }
 
 int RoomPowerLevelsEvent::powerLevelForEvent(const QString &eventId) const {
diff --git a/lib/events/roompowerlevelsevent.h b/lib/events/roompowerlevelsevent.h
index 415cc814..a1638a27 100644
--- a/lib/events/roompowerlevelsevent.h
+++ b/lib/events/roompowerlevelsevent.h
@@ -3,17 +3,16 @@
 
 #pragma once
 
-#include "eventcontent.h"
 #include "stateevent.h"
 
 namespace Quotient {
-class QUOTIENT_API PowerLevelsEventContent : public EventContent::Base {
-public:
+struct QUOTIENT_API PowerLevelsEventContent {
     struct Notifications {
         int room;
     };
 
     explicit PowerLevelsEventContent(const QJsonObject& json);
+    QJsonObject toJson() const;
 
     int invite;
     int kick;
@@ -29,9 +28,6 @@ public:
     int usersDefault;
 
     Notifications notifications;
-
-protected:
-    void fillJson(QJsonObject* o) const override;
 };
 
 class QUOTIENT_API RoomPowerLevelsEvent
diff --git a/lib/events/simplestateevents.h b/lib/events/simplestateevents.h
index 9610574b..33221542 100644
--- a/lib/events/simplestateevents.h
+++ b/lib/events/simplestateevents.h
@@ -4,63 +4,47 @@
 #pragma once
 
 #include "stateevent.h"
+#include "single_key_value.h"
 
 namespace Quotient {
-namespace EventContent {
-    template <typename T>
-    struct SimpleContent {
-        using value_type = T;
-
-        // The constructor is templated to enable perfect forwarding
-        template <typename TT>
-        SimpleContent(QString keyName, TT&& value)
-            : value(std::forward<TT>(value)), key(std::move(keyName))
-        {}
-        SimpleContent(const QJsonObject& json, QString keyName)
-            : value(fromJson<T>(json[keyName])), key(std::move(keyName))
-        {}
-        QJsonObject toJson() const
-        {
-            return { { key, Quotient::toJson(value) } };
-        }
-
-        T value;
-        const QString key;
-    };
-} // namespace EventContent
-
-#define DEFINE_SIMPLE_STATE_EVENT(_Name, _TypeId, _ValueType, _ContentKey)     \
-    class QUOTIENT_API _Name                                                \
-        : public StateEvent<EventContent::SimpleContent<_ValueType>> {         \
-    public:                                                                    \
-        using value_type = content_type::value_type;                           \
-        DEFINE_EVENT_TYPEID(_TypeId, _Name)                                    \
-        template <typename T>                                                  \
-        explicit _Name(T&& value)                                              \
-            : StateEvent(typeId(), matrixTypeId(), QString(),                  \
-                         QStringLiteral(#_ContentKey), std::forward<T>(value)) \
-        {}                                                                     \
-        explicit _Name(QJsonObject obj)                                        \
-            : StateEvent(typeId(), std::move(obj),                             \
-                         QStringLiteral(#_ContentKey))                         \
-        {}                                                                     \
-        auto _ContentKey() const { return content().value; }                   \
-    };                                                                         \
-    REGISTER_EVENT_TYPE(_Name)                                                 \
+#define DEFINE_SIMPLE_STATE_EVENT(_Name, _TypeId, _ValueType, _ContentKey) \
+    constexpr auto _Name##Key = #_ContentKey##_ls;                         \
+    class QUOTIENT_API _Name                                               \
+        : public StateEvent<                                               \
+              EventContent::SingleKeyValue<_ValueType, &_Name##Key>> {     \
+    public:                                                                \
+        using value_type = _ValueType;                                     \
+        DEFINE_EVENT_TYPEID(_TypeId, _Name)                                \
+        template <typename T>                                              \
+        explicit _Name(T&& value)                                          \
+            : StateEvent(TypeId, matrixTypeId(), QString(),                \
+                         std::forward<T>(value))                           \
+        {}                                                                 \
+        explicit _Name(QJsonObject obj)                                    \
+            : StateEvent(TypeId, std::move(obj))                           \
+        {}                                                                 \
+        auto _ContentKey() const { return content().value; }               \
+    };                                                                     \
+    REGISTER_EVENT_TYPE(_Name)                                             \
     // End of macro
 
 DEFINE_SIMPLE_STATE_EVENT(RoomNameEvent, "m.room.name", QString, name)
 DEFINE_SIMPLE_STATE_EVENT(RoomTopicEvent, "m.room.topic", QString, topic)
-DEFINE_SIMPLE_STATE_EVENT(RoomPinnedEvent, "m.room.pinned_messages", QStringList, pinnedEvents)
+DEFINE_SIMPLE_STATE_EVENT(RoomPinnedEvent, "m.room.pinned_messages",
+                          QStringList, pinnedEvents)
 
+constexpr auto RoomAliasesEventKey = "aliases"_ls;
 class [[deprecated(
     "m.room.aliases events are deprecated by the Matrix spec; use"
     " RoomCanonicalAliasEvent::altAliases() to get non-authoritative aliases")]] //
-RoomAliasesEvent : public StateEvent<EventContent::SimpleContent<QStringList>> {
+RoomAliasesEvent
+    : public StateEvent<
+          EventContent::SingleKeyValue<QStringList, &RoomAliasesEventKey>>
+{
 public:
     DEFINE_EVENT_TYPEID("m.room.aliases", RoomAliasesEvent)
     explicit RoomAliasesEvent(const QJsonObject& obj)
-        : StateEvent(typeId(), obj, QStringLiteral("aliases"))
+        : StateEvent(typeId(), obj)
     {}
     QString server() const { return stateKey(); }
     QStringList aliases() const { return content().value; }
diff --git a/lib/events/single_key_value.h b/lib/events/single_key_value.h
new file mode 100644
index 00000000..75ca8cd2
--- /dev/null
+++ b/lib/events/single_key_value.h
@@ -0,0 +1,27 @@
+#pragma once
+
+#include "converters.h"
+
+namespace Quotient {
+
+namespace EventContent {
+    template <typename T, const QLatin1String* KeyStr>
+    struct SingleKeyValue {
+        T value;
+    };
+} // namespace EventContent
+
+template <typename ValueT, const QLatin1String* KeyStr>
+struct JsonConverter<EventContent::SingleKeyValue<ValueT, KeyStr>> {
+    using content_type = EventContent::SingleKeyValue<ValueT, KeyStr>;
+    static content_type load(const QJsonValue& jv)
+    {
+        return { fromJson<ValueT>(jv.toObject().value(JsonKey)) };
+    }
+    static QJsonObject dump(const content_type& c)
+    {
+        return { { JsonKey, toJson(c.value) } };
+    }
+    static inline const auto JsonKey = toSnakeCase(*KeyStr);
+};
+} // namespace Quotient
diff --git a/lib/events/stateevent.cpp b/lib/events/stateevent.cpp
index e53d47d4..c343e37f 100644
--- a/lib/events/stateevent.cpp
+++ b/lib/events/stateevent.cpp
@@ -6,9 +6,9 @@
 using namespace Quotient;
 
 StateEventBase::StateEventBase(Type type, const QJsonObject& json)
-    : RoomEvent(json.contains(StateKeyKeyL) ? type : unknownEventTypeId(), json)
+    : RoomEvent(json.contains(StateKeyKeyL) ? type : UnknownEventTypeId, json)
 {
-    if (Event::type() == unknownEventTypeId() && !json.contains(StateKeyKeyL))
+    if (Event::type() == UnknownEventTypeId && !json.contains(StateKeyKeyL))
         qWarning(EVENTS) << "Attempt to create a state event with no stateKey -"
                             "forcing the event type to unknown to avoid damage";
 }
@@ -16,7 +16,7 @@ StateEventBase::StateEventBase(Type type, const QJsonObject& json)
 StateEventBase::StateEventBase(Event::Type type, event_mtype_t matrixType,
                                const QString& stateKey,
                                const QJsonObject& contentJson)
-    : RoomEvent(type, basicStateEventJson(matrixType, contentJson, stateKey))
+    : RoomEvent(type, basicJson(matrixType, contentJson, stateKey))
 {}
 
 bool StateEventBase::repeatsState() const
diff --git a/lib/events/stateevent.h b/lib/events/stateevent.h
index 88da68f8..343e87a5 100644
--- a/lib/events/stateevent.h
+++ b/lib/events/stateevent.h
@@ -7,16 +7,6 @@
 
 namespace Quotient {
 
-/// Make a minimal correct Matrix state event JSON
-inline QJsonObject basicStateEventJson(const QString& matrixTypeId,
-                                       const QJsonObject& content,
-                                       const QString& stateKey = {})
-{
-    return { { TypeKey, matrixTypeId },
-             { StateKeyKey, stateKey },
-             { ContentKey, content } };
-}
-
 class QUOTIENT_API StateEventBase : public RoomEvent {
 public:
     static inline EventFactory<StateEventBase> factory { "StateEvent" };
@@ -27,6 +17,16 @@ public:
                    const QJsonObject& contentJson = {});
     ~StateEventBase() override = default;
 
+    //! Make a minimal correct Matrix state event JSON
+    static QJsonObject basicJson(const QString& matrixTypeId,
+                                 const QJsonObject& content,
+                                 const QString& stateKey = {})
+    {
+        return { { TypeKey, matrixTypeId },
+                 { StateKeyKey, stateKey },
+                 { ContentKey, content } };
+    }
+
     bool isStateEvent() const override { return true; }
     QString replacedState() const;
     void dumpTo(QDebug dbg) const override;
@@ -36,6 +36,14 @@ public:
 using StateEventPtr = event_ptr_tt<StateEventBase>;
 using StateEvents = EventsArray<StateEventBase>;
 
+[[deprecated("Use StateEventBase::basicJson() instead")]]
+inline QJsonObject basicStateEventJson(const QString& matrixTypeId,
+                                       const QJsonObject& content,
+                                       const QString& stateKey = {})
+{
+    return StateEventBase::basicJson(matrixTypeId, content, stateKey);
+}
+
 //! \brief Override RoomEvent factory with that from StateEventBase if JSON has
 //! stateKey
 //!
@@ -64,7 +72,7 @@ inline bool is<StateEventBase>(const Event& e)
  * \sa
  * https://matrix.org/docs/spec/client_server/unstable.html#types-of-room-events
  */
-using StateEventKey = QPair<QString, QString>;
+using StateEventKey = std::pair<QString, QString>;
 
 template <typename ContentT>
 struct Prev {
@@ -72,7 +80,7 @@ struct Prev {
     explicit Prev(const QJsonObject& unsignedJson,
                   ContentParamTs&&... contentParams)
         : senderId(unsignedJson.value("prev_sender"_ls).toString())
-        , content(unsignedJson.value(PrevContentKeyL).toObject(),
+        , content(fromJson<ContentT>(unsignedJson.value(PrevContentKeyL)),
                   std::forward<ContentParamTs>(contentParams)...)
     {}
 
@@ -89,7 +97,8 @@ public:
     explicit StateEvent(Type type, const QJsonObject& fullJson,
                         ContentParamTs&&... contentParams)
         : StateEventBase(type, fullJson)
-        , _content(contentJson(), std::forward<ContentParamTs>(contentParams)...)
+        , _content(fromJson<ContentT>(contentJson()),
+                   std::forward<ContentParamTs>(contentParams)...)
     {
         const auto& unsignedData = unsignedJson();
         if (unsignedData.contains(PrevContentKeyL))
@@ -101,9 +110,9 @@ public:
                         const QString& stateKey,
                         ContentParamTs&&... contentParams)
         : StateEventBase(type, matrixType, stateKey)
-        , _content(std::forward<ContentParamTs>(contentParams)...)
+        , _content{std::forward<ContentParamTs>(contentParams)...}
     {
-        editJson().insert(ContentKey, _content.toJson());
+        editJson().insert(ContentKey, toJson(_content));
     }
 
     const ContentT& content() const { return _content; }
@@ -111,7 +120,7 @@ public:
     void editContent(VisitorT&& visitor)
     {
         visitor(_content);
-        editJson()[ContentKeyL] = _content.toJson();
+        editJson()[ContentKeyL] = toJson(_content);
     }
     const ContentT* prevContent() const
     {