Adapt build against qt6

CMakeLists.txt

@@ -46,6 +46,9 @@ ecm_setup_version(PROJECT VARIABLE_PREFIX KPIMTEXTEDIT
 )
 
 set(QT_REQUIRED_VERSION "5.15.2")
+if (QT_MAJOR_VERSION STREQUAL "6")
+    set(QT_REQUIRED_VERSION "6.4.0")
+endif()	
 find_package(Qt${QT_MAJOR_VERSION} ${QT_REQUIRED_VERSION} CONFIG REQUIRED COMPONENTS Widgets)
 
 ########### Find packages ###########

src/texttospeech/texttospeech.cpp

@@ -62,8 +62,13 @@ void TextToSpeech::slotStateChanged()
     case QTextToSpeech::Paused:
         state = TextToSpeech::Paused;
         break;
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     case QTextToSpeech::BackendError:
         state = TextToSpeech::BackendError;
+#else
+    case QTextToSpeech::Error:
+        state = TextToSpeech::BackendError;
+#endif
         break;
     }
     Q_EMIT stateChanged(state);
@@ -71,7 +76,11 @@ void TextToSpeech::slotStateChanged()
 
 bool TextToSpeech::isReady() const
 {
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     return mTextToSpeech->state() != QTextToSpeech::BackendError;
+#else
+    return mTextToSpeech->state() != QTextToSpeech::Error;
+#endif
 }
 
 void TextToSpeech::say(const QString &text)