musredit help system if neither QWebEngine nor QWebKit is found.

If neither QWebEngine nor QWebKit is found, do not generate an build
error anymore. Instead just show a default window stating that
the help system is not available due to missing Qt web libs.

src/musredit_qt5/musredit/CMakeLists.txt

@@ -5,16 +5,20 @@ find_package(Qt5WebEngine QUIET)
 find_package(Qt5WebKit QUIET)
 
 set(qt_libs Qt5::Core Qt5::Widgets Qt5::Network Qt5::Xml Qt5::Svg Qt5::PrintSupport)
+set(Qt5NoWeb 0)
 if (Qt5WebEngine_FOUND)
   message("-- Qt5WebEngine is present.")
   find_package(Qt5WebEngineWidgets QUIET CONFIG REQUIRED)
   set(qt_libs ${qt_libs} Qt5::WebEngine Qt5::WebEngineWidgets)
+  # unset a potentially found Qt5Webkit
+  unset(Qt5WebKit_FOUND)
 elseif (Qt5WebKit_FOUND)
   message("-- Qt5WebKit is present.")
   find_package(Qt5WebKitWidgets QUIET CONFIG REQUIRED)
   set(qt_libs ${qt_libs} Qt5::WebKit Qt5::WebKitWidgets)
 else (Qt5WebEngine_FOUND)
   message("-- Neither Qt5WebEngine nor Qt5WebKit found.")
+  set(Qt5NoWeb 1)
 endif (Qt5WebEngine_FOUND)
 
 set(musredit_src
@@ -116,6 +120,15 @@ else (APPLE)
   )
 endif (APPLE)
 
+# set necessary tags depending if QtWebEngine, QtWebKit, 
+# or none of both are given
+if (Qt5WebKit_FOUND)
+  target_compile_options(musredit
+    BEFORE PRIVATE 
+    -DHAVE_QT_WEB_KIT
+  )
+endif (Qt5WebKit_FOUND)
+
 if (Qt5WebEngine_FOUND)
   target_compile_options(musredit
     BEFORE PRIVATE 
@@ -123,6 +136,13 @@ if (Qt5WebEngine_FOUND)
   )
 endif (Qt5WebEngine_FOUND)
 
+if (Qt5NoWeb)
+  target_compile_options(musredit
+    BEFORE PRIVATE 
+    -DHAVE_QT_NO_WEB
+  )
+endif (Qt5NoWeb)
+
 target_include_directories(musredit
   BEFORE PRIVATE
   $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}>

src/musredit_qt5/musredit/PHelp.cpp

@@ -30,9 +30,13 @@
 #include <QtWidgets>
 #ifdef HAVE_QT_WEB_ENGINE
 #include <QWebEngineView>
-#else
+#endif
+#ifdef HAVE_QT_WEB_KIT
 #include <QtWebKitWidgets>
 #endif
+#ifdef HAVE_QT_NO_WEB
+#include <QPlainTextEdit>
+#endif
 #include <QNetworkProxyFactory>
 
 #include <QtDebug>
@@ -61,14 +65,24 @@ PHelp::PHelp(const QString &url, const bool isDarkTheme) :
 
 #ifdef HAVE_QT_WEB_ENGINE
   fView = new QWebEngineView(this);
-#else
+#endif
+#ifdef HAVE_QT_WEB_KIT
   fView = new QWebView(this);
 #endif
+#ifdef HAVE_QT_NO_WEB
+  fView = new QPlainTextEdit(this);
+#endif
+#ifndef HAVE_QT_NO_WEB
   fView->load(QUrl(url));
   connect(fView, SIGNAL(loadFinished(bool)), SLOT(adjustLocation()));
   connect(fView, SIGNAL(titleChanged(QString)), SLOT(adjustTitle()));
   connect(fView, SIGNAL(loadProgress(int)), SLOT(setProgress(int)));
   connect(fView, SIGNAL(loadFinished(bool)), SLOT(finishLoading(bool)));
+#else
+  fView->setPlainText("Within the current setup there is NO Help available.");
+  fView->appendPlainText("The necessary Qt web libs where not found when setting up musredit.");
+  fView->setReadOnly(true);
+#endif
 
   fLocationEdit = new QLineEdit(this);
   fLocationEdit->setSizePolicy(QSizePolicy::Expanding, fLocationEdit->sizePolicy().verticalPolicy());
@@ -80,7 +94,8 @@ PHelp::PHelp(const QString &url, const bool isDarkTheme) :
   toolBar->addAction(fView->pageAction(QWebEnginePage::Forward));
   toolBar->addAction(fView->pageAction(QWebEnginePage::Reload));
   toolBar->addAction(fView->pageAction(QWebEnginePage::Stop));
-#else
+#endif
+#ifdef HAVE_QT_WEB_KIT
   toolBar->addAction(fView->pageAction(QWebPage::Back));
   toolBar->addAction(fView->pageAction(QWebPage::Forward));
   toolBar->addAction(fView->pageAction(QWebPage::Reload));
@@ -127,7 +142,9 @@ void PHelp::done()
  */
 void PHelp::adjustLocation()
 {
+#ifndef HAVE_QT_NO_WEB
   fLocationEdit->setText(fView->url().toString());
+#endif
 }
 
 //---------------------------------------------------------------------------
@@ -138,8 +155,10 @@ void PHelp::adjustLocation()
 void PHelp::changeLocation()
 {
   QUrl url = QUrl(fLocationEdit->text());
+#ifndef HAVE_QT_NO_WEB
   fView->load(url);
   fView->setFocus();
+#endif
 }
 
 //---------------------------------------------------------------------------
@@ -149,10 +168,12 @@ void PHelp::changeLocation()
  */
 void PHelp::adjustTitle()
 {
+#ifndef HAVE_QT_NO_WEB
   if (fProgress <= 0 || fProgress >= 100)
     setWindowTitle(fView->title());  
   else
     setWindowTitle(QString("%1 (%2%)").arg(fView->title()).arg(fProgress));
+#endif
 }
 
 //---------------------------------------------------------------------------

src/musredit_qt5/musredit/PHelp.h

@@ -34,7 +34,8 @@
 
 #ifdef HAVE_QT_WEB_ENGINE
 class QWebEngineView;
-#else
+#endif
+#ifdef HAVE_QT_WEB_KIT
 class QWebView;
 #endif
 QT_BEGIN_NAMESPACE
@@ -66,8 +67,12 @@ class PHelp : public QMainWindow
     bool fDarkTheme;
 #ifdef HAVE_QT_WEB_ENGINE
     QWebEngineView *fView; ///< web viewer
-#else
+#endif
+#ifdef HAVE_QT_WEB_KIT
     QWebView *fView; ///< web viewer
+#endif
+#ifdef HAVE_QT_NO_WEB
+    QPlainTextEdit *fView; ///< dialog stating that there is NO web viewer
 #endif
     QLineEdit *fLocationEdit; ///< url address line edit
     int fProgress; ///< progress value (0-100) while loading an url