port LAMMPS GUI to Qt6 while still supporting Qt5

tools/lammps-gui/CMakeLists.txt

@@ -11,6 +11,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 option(LAMMPS_GUI_USE_PLUGIN "Load LAMMPS library dynamically at runtime" OFF)
 mark_as_advanced(LAMMPS_GUI_USE_PLUGIN)
+option(LAMMPS_GUI_USE_QT5 "Prefer using Qt5 over Qt6" OFF)
 
 # checks
 # when this file is included as subdirectory in the LAMMPS build, many settings are directly imported
@@ -73,7 +74,15 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
 endif()
 
 # we require Qt 5 and at least version 5.12 at that.
+if(NOT LAMMPS_GUI_USE_QT5)
+  find_package(Qt6 6.2 COMPONENTS Widgets Charts)
+endif()
+if(NOT Qt6_FOUND)
   find_package(Qt5 5.12 REQUIRED COMPONENTS Widgets Charts)
+  set(QT_VERSION_MAJOR "5")
+else()
+  set(QT_VERSION_MAJOR "6")
+endif()
 
 set(PROJECT_SOURCES
   main.cpp
@@ -105,7 +114,11 @@ set(PROJECT_SOURCES
   ${PLUGIN_LOADER_SRC}
   ${ICON_RC_FILE}
 )
+if(QT_VERSION_MAJOR EQUAL 6)
+  qt6_add_resources(PROJECT_SOURCES lammpsgui.qrc)
+else()
   qt5_add_resources(PROJECT_SOURCES lammpsgui.qrc)
+endif()
 
 if(APPLE)
   set(MACOSX_ICON_FILE ${LAMMPS_DIR}/cmake/packaging/lammps.icns)
@@ -113,10 +126,22 @@ if(APPLE)
   set(MACOSX_BACKGROUND_FILE ${LAMMPS_DIR}/cmake/packaging/LAMMPS_DMG_Background.png)
 endif()
 
+if(QT_VERSION_MAJOR EQUAL 6)
+  qt_add_executable(lammps-gui
+    MANUAL_FINALIZATION
+    ${MACOSX_ICON_FILE}
+    ${PROJECT_SOURCES}
+  )
+else()
   add_executable(lammps-gui
     ${MACOSX_ICON_FILE}
     ${PROJECT_SOURCES}
   )
+endif()
+
+if(QT_VERSION_MAJOR EQUAL 6)
+    qt_finalize_executable(lammps-gui)
+endif()
 
 # compilation settings
 if(LAMMPS_GUI_USE_PLUGIN)
@@ -128,7 +153,7 @@ else()
 endif()
 target_include_directories(lammps-gui PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 target_compile_definitions(lammps-gui PRIVATE LAMMPS_GUI_VERSION="${PROJECT_VERSION}")
-target_link_libraries(lammps-gui PRIVATE Qt5::Widgets Qt5::Charts)
+target_link_libraries(lammps-gui PRIVATE Qt${QT_VERSION_MAJOR}::Widgets Qt${VERSION_MAJOR}::Charts)
 if(BUILD_OMP)
   find_package(OpenMP COMPONENTS CXX REQUIRED)
   target_link_libraries(lammps-gui PRIVATE OpenMP::OpenMP_CXX)
@@ -209,7 +234,7 @@ elseif((CMAKE_SYSTEM_NAME STREQUAL "Windows") AND CMAKE_CROSSCOMPILING)
     COMMENT "Create zip file with windows binaries"
     BYPRODUCT LAMMPS-Win10-amd64.zip
     WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
-elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+elseif((CMAKE_SYSTEM_NAME STREQUAL "Linux") AND NOT LAMMPS_GUI_USE_PLUGIN)
   install(TARGETS lammps-gui DESTINATION ${CMAKE_INSTALL_BINDIR})
   install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/lammps-gui.desktop DESTINATION ${CMAKE_INSTALL_DATADIR}/applications/)
   install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/lammps-input.xml DESTINATION ${CMAKE_INSTALL_DATADIR}/mime/packages/)

tools/lammps-gui/chartviewer.cpp

@@ -15,11 +15,19 @@
 
 #include "lammpsgui.h"
 
+#include <QAction>
+#include <QApplication>
+#include <QFileDialog>
 #include <QHBoxLayout>
+#include <QLabel>
+#include <QLayout>
 #include <QLineSeries>
+#include <QMenu>
+#include <QMenuBar>
 #include <QPushButton>
 #include <QSettings>
 #include <QSpacerItem>
+#include <QTextStream>
 #include <QVBoxLayout>
 
 using namespace QtCharts;
@@ -288,7 +296,7 @@ void ChartViewer::add_data(int step, double data)
     if (last_step < step) {
         last_step = step;
         series->append(step, data);
-        auto points = series->pointsVector();
+        auto points = series->points();
 
         qreal xmin = 1.0e100;
         qreal xmax = -1.0e100;
@@ -309,7 +317,7 @@ void ChartViewer::add_data(int step, double data)
 
 void ChartViewer::reset_zoom()
 {
-    auto points = series->pointsVector();
+    auto points = series->points();
 
     qreal xmin = 1.0e100;
     qreal xmax = -1.0e100;

tools/lammps-gui/chartviewer.h

@@ -14,16 +14,17 @@
 #ifndef CHARTVIEWER_H
 #define CHARTVIEWER_H
 
+#include <QComboBox>
 #include <QList>
 #include <QString>
 #include <QWidget>
-#include <QtCharts>
 
 class QAction;
 class QMenuBar;
 class QMenu;
-class QComboBox;
+namespace QtCharts {
 class ChartViewer;
+}
 
 class ChartWindow : public QWidget {
     Q_OBJECT
@@ -64,12 +65,18 @@ private:
     QAction *closeAct, *stopAct, *quitAct;
 
     QString filename;
-    QList<ChartViewer *> charts;
+    QList<QtCharts::ChartViewer *> charts;
 };
 
 /* -------------------------------------------------------------------- */
 
-class ChartViewer : public QtCharts::QChartView {
+#include <QChart>
+#include <QChartView>
+#include <QLineSeries>
+#include <QValueAxis>
+
+namespace QtCharts {
+class ChartViewer : public QChartView {
     Q_OBJECT
 
 public:
@@ -86,11 +93,12 @@ public:
 
 private:
     int last_step, index;
-    QtCharts::QChart *chart;
-    QtCharts::QLineSeries *series;
-    QtCharts::QValueAxis *xaxis;
-    QtCharts::QValueAxis *yaxis;
+    QChart *chart;
+    QLineSeries *series;
+    QValueAxis *xaxis;
+    QValueAxis *yaxis;
 };
+} // namespace QtCharts
 #endif
 
 // Local Variables:

tools/lammps-gui/lammpsgui.cpp

@@ -35,6 +35,7 @@
 #include <QLabel>
 #include <QLocale>
 #include <QMessageBox>
+#include <QMetaType>
 #include <QPlainTextEdit>
 #include <QProcess>
 #include <QProgressBar>
@@ -69,8 +70,10 @@ LammpsGui::LammpsGui(QWidget *parent, const char *filename) :
     // enforce using the plain ASCII C locale within the GUI.
     QLocale::setDefault(QLocale("C"));
 
-    // register QList<QString>
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    // register QList<QString> only needed for Qt5
     qRegisterMetaTypeStreamOperators<QList<QString>>("QList<QString>");
+#endif
 
     ui->setupUi(this);
     this->setCentralWidget(ui->textEdit);
@@ -588,7 +591,8 @@ void LammpsGui::open_file(const QString &fileName)
     if (!file.open(QIODevice::ReadOnly | QFile::Text)) {
         QMessageBox::warning(this, "Warning",
                              "Cannot open file " + path.absoluteFilePath() + ": " +
-                                 file.errorString() + ".\nWill create new file on saving editor buffer.");
+                                 file.errorString() +
+                                 ".\nWill create new file on saving editor buffer.");
         ui->textEdit->document()->setPlainText(QString());
     } else {
         QTextStream in(&file);
@@ -1039,9 +1043,9 @@ void LammpsGui::do_run(bool use_buffer)
     logwindow->document()->setDefaultFont(text_font);
     logwindow->setLineWrapMode(LogWindow::NoWrap);
     logwindow->setMinimumSize(400, 300);
-    QShortcut *shortcut = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_W), logwindow);
+    QShortcut *shortcut = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_W), logwindow);
     QObject::connect(shortcut, &QShortcut::activated, logwindow, &LogWindow::close);
-    shortcut = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_Slash), logwindow);
+    shortcut = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_Slash), logwindow);
     QObject::connect(shortcut, &QShortcut::activated, this, &LammpsGui::stop_run);
     if (settings.value("viewlog", true).toBool())
         logwindow->show();
@@ -1058,9 +1062,9 @@ void LammpsGui::do_run(bool use_buffer)
             .arg(run_counter));
     chartwindow->setWindowIcon(QIcon(":/icons/lammps-icon-128x128.png"));
     chartwindow->setMinimumSize(400, 300);
-    shortcut = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_W), chartwindow);
+    shortcut = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_W), chartwindow);
     QObject::connect(shortcut, &QShortcut::activated, chartwindow, &ChartWindow::close);
-    shortcut = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_Slash), chartwindow);
+    shortcut = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_Slash), chartwindow);
     QObject::connect(shortcut, &QShortcut::activated, this, &LammpsGui::stop_run);
     if (settings.value("viewchart", true).toBool())
         chartwindow->show();

tools/lammps-gui/lammpsgui.h

@@ -16,8 +16,10 @@
 
 #include <QMainWindow>
 
+#include <QGridLayout>
 #include <QList>
 #include <QPair>
+#include <QSpacerItem>
 #include <QString>
 #include <vector>