Provide a colour code for the user

Contributes to #296

Author: a-andreyev

lib/user.cpp

@@ -33,6 +33,9 @@
 #include <QtCore/QStringBuilder>
 #include <QtCore/QElapsedTimer>
 
+#include <QtCore/QCryptographicHash>
+#include <QtCore/QtEndian>
+
 #include <functional>
 
 using namespace QMatrixClient;
@@ -47,8 +50,21 @@ class User::Private
             return Avatar(move(url));
         }
 
+        qreal makeHueF(QString userId)
+        {
+            QByteArray hash = QCryptographicHash::hash(userId.toUtf8(),
+                                                       QCryptographicHash::Sha1);
+            QDataStream dataStream(qToLittleEndian(hash).left(2));
+            dataStream.setByteOrder(QDataStream::LittleEndian);
+            quint16 hashValue;
+            dataStream >> hashValue;
+            qreal hueF = static_cast<qreal>(hashValue)/std::numeric_limits<quint16>::max();
+            Q_ASSERT((0 <= hueF) && (hueF <= 1));
+            return hueF;
+        }
+
         Private(QString userId, Connection* connection)
-            : userId(move(userId)), connection(connection)
+            : userId(move(userId)), connection(connection), hueF(makeHueF(userId))
         { }
 
         QString userId;
@@ -57,6 +73,7 @@ class User::Private
         QString bridged;
         QString mostUsedName;
         QMultiHash<QString, const Room*> otherNames;
+        qreal hueF;
         Avatar mostUsedAvatar { makeAvatar({}) };
         std::vector<Avatar> otherAvatars;
         auto otherAvatar(QUrl url)
@@ -219,6 +236,11 @@ bool User::isGuest() const
     return *it == ':';
 }
 
+int User::hue() const
+{
+    return int(hueF()*359);
+}
+
 QString User::name(const Room* room) const
 {
     return d->nameForRoom(room);
@@ -424,3 +446,7 @@ void User::processEvent(const RoomMemberEvent& event, const Room* room)
         updateAvatarUrl(event.avatarUrl(), d->avatarUrlForRoom(room), room);
     }
 }
+
+qreal User::hueF() const {
+    return d->hueF;
+}

lib/user.h

@@ -33,6 +33,8 @@ namespace QMatrixClient
             Q_OBJECT
             Q_PROPERTY(QString id READ id CONSTANT)
             Q_PROPERTY(bool isGuest READ isGuest CONSTANT)
+            Q_PROPERTY(int hue READ hue CONSTANT)
+            Q_PROPERTY(qreal hueF READ hueF CONSTANT)
             Q_PROPERTY(QString name READ name NOTIFY nameChanged)
             Q_PROPERTY(QString displayName READ displayname NOTIFY nameChanged STORED false)
             Q_PROPERTY(QString fullName READ fullName NOTIFY nameChanged STORED false)
@@ -95,6 +97,15 @@ namespace QMatrixClient
              */
             bool isGuest() const;
 
+            /** Hue color component of this user based on id.
+             * The implementation is based on XEP-0392:
+             * https://xmpp.org/extensions/xep-0392.html
+             * Naming and ranges are the same as QColor's hue methods:
+             * https://doc.qt.io/qt-5/qcolor.html#integer-vs-floating-point-precision
+             */
+            int hue() const;
+            qreal hueF() const;
+
             const Avatar& avatarObject(const Room* room = nullptr) const;
             Q_INVOKABLE QImage avatar(int dimension, const Room* room = nullptr);
             Q_INVOKABLE QImage avatar(int requestedWidth, int requestedHeight,