Core: add a 'suffixAfter' function

Pure convenience for the decomposition of ids constructed wit suffix().
This will help centralizing repeated code in the qnx, blackberry, android
and cmake plugins.

Change-Id: Ibc9ca21f8da1d15578f4553da97212cc99a5c5b9
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/coreplugin/id.cpp

@@ -283,6 +283,12 @@ Id Id::withSuffix(const char *suffix) const
     return Id(ba.constData());
 }
 
+/*!
+  \overload
+
+  \sa stringSuffix()
+*/
+
 Id Id::withSuffix(const QString &suffix) const
 {
     const QByteArray ba = name() + suffix.toUtf8();
@@ -340,4 +346,20 @@ bool Id::alphabeticallyBefore(Id other) const
     return toString().compare(other.toString(), Qt::CaseInsensitive) < 0;
 }
 
+
+/*!
+  Convenience function to extract a part of the id string
+  representation. This can be used to split off the base
+  part used when generating an id with \c{withSuffix()}.
+
+  \sa withSuffix()
+*/
+
+QString Id::suffixAfter(Id baseId) const
+{
+    const QByteArray b = baseId.name();
+    const QByteArray n = name();
+    return n.startsWith(b) ? QString::fromUtf8(n.mid(b.size())) : QString();
+}
+
 } // namespace Core

src/plugins/coreplugin/id.h

@@ -57,6 +57,7 @@ public:
     QByteArray name() const;
     QString toString() const; // Avoid.
     QVariant toSetting() const; // Good to use.
+    QString suffixAfter(Id baseId) const;
     bool isValid() const { return m_id; }
     bool operator==(Id id) const { return m_id == id.m_id; }
     bool operator==(const char *name) const;