More small Qt6 changes (reduce warnings)

-also improve building instructions

BUILDING.md

@@ -75,15 +75,16 @@ sudo apt install build-essential cmake zlib1g-dev libgl1-mesa-dev libdrm-dev gcc
 
 ##### Qt6
 
-Ubuntu 22.04 comes with Qt5.15 and Qt6.2.  
+Ubuntu 22.04 comes with Qt5.15 and Qt6.2. To build with Qt6:
 
 ```
 sudo apt install build-essential cmake zlib1g-dev libgl1-mesa-dev libdrm-dev gcc g++ \
                  graphviz doxygen gettext git \
                  qt6-base-dev qt6-tools-dev qt6-tools-dev-tools qt6-l10n-tools linguist-qt6 libqt6svg6-dev \
                  qt6-multimedia-dev libqt6serialport6-dev \
-                 libqt6positioning6-plugins libgps-dev \
-                 libqt6webenginewidgets6 qt6-webengine-dev-tools libqt6charts6-dev
+                 qt6-positioning-dev libqt6positioning6-plugins libgps-dev \
+                 libqt6webchannel6-dev libqt6webenginewidgets6 qt6-webengine-dev qt6-webengine-dev-tools \
+                 libqt6charts6-dev
 ```
 
 

src/core/StelOBJ.cpp

@@ -961,8 +961,8 @@ bool StelOBJ::load(QIODevice& device, const QString &basePath, const VertexOrder
 
 	qCDebug(stelOBJ)<<"Loaded OBJ in"<<timer.elapsed()<<"ms";
 	qCDebug(stelOBJ, "Parsed %d positions, %d normals, %d texture coordinates, %d materials",
-		posList.size(), normalList.size(), texList.size(), m_materials.size());
-	qCDebug(stelOBJ, "Created %d vertices, %d faces, %d objects", m_vertices.size(), getFaceCount(), m_objects.size());
+		int(posList.size()), int(normalList.size()), int(texList.size()), int(m_materials.size()));
+	qCDebug(stelOBJ, "Created %d vertices, %d faces, %d objects", int(m_vertices.size()), getFaceCount(), int(m_objects.size()));
 
 	//perform post processing
 	performPostProcessing(normalList.isEmpty());

src/main.cpp

@@ -166,8 +166,10 @@ int main(int argc, char **argv)
 	QCoreApplication::setOrganizationName("stellarium");
 
 	// Support high DPI pixmaps and fonts
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 	QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps, true);
 	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
+#endif
 	if (argList.contains("--scale-gui")) // Variable QT_SCALE_FACTOR should be defined before app will be created!
 		qputenv("QT_SCALE_FACTOR", CLIProcessor::argsGetOptionWithArg(argList, "", "--scale-gui", "").toString().toLatin1());