DatabaseWindow has no knowledge more of the existence of QueryTab but user can still create and use them within that window.

pglab/plugin_support/IPluginContentWidgetContext.h

@@ -47,6 +47,10 @@ public:
 
 	virtual void addContentWidget(PluginContentWidget *widget) = 0;
 
+	/** Return a widget you can use as a parent
+	 */
+	virtual QWidget* container() = 0;
+
 	template<typename T, class...Args>
 	bool addObjects(Args&&...args);
 	template<typename T>

pglab/plugin_support/LMainWindow.cpp

@@ -0,0 +1,220 @@
+#include "LMainWindow.h"
+#include "PluginContentWidget.h"
+#include "PluginContentWidgetContextBase.h"
+#include "PluginModule.h"
+#include "PluginRegister.h"
+
+#include <QDebug>
+#include <QMenuBar>
+#include <QStatusBar>
+#include <QToolBar>
+
+namespace LMainWindow_details {
+
+	class LMainWindowContentContext: public PluginContentWidgetContextBase {
+	public:
+		explicit LMainWindowContentContext(LMainWindow *window)
+			: m_window(window)
+		{}
+
+		void setCaption(PluginContentWidget *content, const QString &caption, const QString &hint = {}) override
+		{
+			m_window->setTabCaptionForWidget(content, caption, hint);
+		}
+
+		void setIcon(PluginContentWidget *content, const QString &iconname) override
+		{
+			m_window->setTabIcon(content, iconname);
+		}
+
+		void showStatusMessage(const QString &msg) override
+		{
+			m_window->statusBar()->showMessage(msg);
+		}
+
+		void addContentWidget(PluginContentWidget *widget) override
+		{
+			m_window->addPage(widget, "");
+		}
+
+		QWidget* container() override
+		{
+			return m_window;
+		}
+	private:
+		LMainWindow *m_window;
+	};
+
+}
+using namespace LMainWindow_details;
+
+
+LMainWindow::LMainWindow(QWidget *parent)
+	: QMainWindow(parent)
+{
+	m_context = new LMainWindowContentContext(this);
+
+	m_tabWidget = new QTabWidget(this);
+	m_tabWidget->setObjectName(QString::fromUtf8("tabWidget"));
+	m_tabWidget->setDocumentMode(true);
+
+	setCentralWidget(m_tabWidget);
+
+	// menu
+	auto menuBar = new QMenuBar(this);
+	setMenuBar(menuBar);
+
+	// tooolbar
+	m_mainToolBar = new QToolBar(this);
+	addToolBar(Qt::TopToolBarArea, m_mainToolBar);
+
+	// statusbar
+	auto statusBar = new QStatusBar(this);
+	setStatusBar(statusBar);
+
+	m_fileMenu = new QMenu("File", this);
+
+	createActions();
+	m_mainToolBar->addAction(m_closeAction);
+
+	connect(m_tabWidget, &QTabWidget::tabCloseRequested, this, &LMainWindow::tabWidget_tabCloseRequested);
+	connect(m_tabWidget, &QTabWidget::currentChanged, this, &LMainWindow::tabWidget_currentChanged);
+}
+
+LMainWindow::~LMainWindow()
+{
+	delete m_context;
+}
+
+void LMainWindow::initModuleMenus()
+{
+	menuBar()->addMenu(m_fileMenu);
+	addModuleMenuActions();
+}
+
+void LMainWindow::addModuleMenuActions()
+{
+	auto reg = PluginRegister::getInstance();
+	auto mods = reg->modules();
+	for (auto && mod : mods) {
+		auto items = mod.second->menuActions();
+		for (auto && item : items) {
+			addMenuAction(item);
+		}
+	}
+}
+
+void LMainWindow::createActions()
+{
+	{
+		auto action = m_closeAction = new QAction(this);
+		QIcon icon;
+		icon.addFile(QString::fromUtf8(":/icons/page_white_delete.png"), QSize(), QIcon::Normal, QIcon::On);
+		action->setIcon(icon);
+		connect(m_closeAction, &QAction::triggered, this, &LMainWindow::actionClose_triggered);
+	}
+
+}
+
+
+void LMainWindow::addMenuAction(const MenuAction &ma)
+{
+	qDebug() << "add action " << ma.text();
+	//auto ac =
+	m_fileMenu->addAction(ma.icon(), ma.text(),
+					[ma, this] ()
+		{
+			ma.perform(m_context);
+		},
+		ma.shortCut());
+
+
+//	auto ac = new QAction(this);
+//	ac->
+}
+
+void LMainWindow::actionClose_triggered()
+{
+	m_tabWidget->tabCloseRequested(m_tabWidget->currentIndex());
+}
+
+
+void LMainWindow::addPage(PluginContentWidget* page, QString caption)
+{
+	m_tabWidget->addTab(page, caption);
+	m_tabWidget->setCurrentWidget(page);
+}
+
+void LMainWindow::setTabCaptionForWidget(QWidget *widget, const QString &caption, const QString &hint)
+{
+	auto index = m_tabWidget->indexOf(widget);
+	m_tabWidget->setTabText(index, caption);
+	m_tabWidget->setTabToolTip(index, hint);
+}
+
+void LMainWindow::setTabIcon(QWidget *widget, const QString &iconname)
+{
+	auto index = m_tabWidget->indexOf(widget);
+	auto n = ":/icons/16x16/" + iconname;
+	m_tabWidget->setTabIcon(index, QIcon(n));
+}
+
+IPluginContentWidgetContext* LMainWindow::context()
+{
+	return m_context;
+}
+
+void LMainWindow::tabWidget_tabCloseRequested(int index)
+{
+	QWidget *widget = m_tabWidget->widget(index);
+	PluginContentWidget *plg_page = dynamic_cast<PluginContentWidget*>(widget);
+	if (plg_page) {
+		if (plg_page->canClose()) {
+			m_tabWidget->removeTab(index);
+			delete plg_page;
+		}
+	}
+	else {
+		// old behaviour shouldn't be needed any more when all pages have been migrated
+		// to PlgPage
+		m_tabWidget->removeTab(index);
+		delete widget;
+	}
+}
+
+void LMainWindow::tabWidget_currentChanged(int index)
+{
+	// remove buttons of old page
+	if (m_previousPage) {
+		removeToolBarButtonsForPage(m_previousPage);
+	}
+
+	// add buttons of new page
+	PluginContentWidget * page = nullptr;
+	if (index >= 0) {
+		QWidget *widget = m_tabWidget->widget(index);
+		page = dynamic_cast<PluginContentWidget*>(widget);
+		if (page) {
+			addToolBarButtonsForPage(page);
+		}
+	}
+	m_previousPage = page;
+}
+
+void LMainWindow::addToolBarButtonsForPage(PluginContentWidget *page)
+{
+	std::vector<QAction*> actions = page->getToolbarActions();
+	QList<QAction*> list;
+	for (auto act : actions) {
+		list.append(act);
+	}
+	m_mainToolBar->addActions(list);
+}
+
+void LMainWindow::removeToolBarButtonsForPage(PluginContentWidget *page)
+{
+	std::vector<QAction*> actions = page->getToolbarActions();
+	for (auto act : actions) {
+		m_mainToolBar->removeAction(act);
+	}
+}

pglab/plugin_support/LMainWindow.h

@@ -0,0 +1,58 @@
+#ifndef LMAINWINDOW_H
+#define LMAINWINDOW_H
+
+#include <QMainWindow>
+
+class IPluginContentWidgetContext;
+class MenuAction;
+class PluginContentWidget;
+
+namespace LMainWindow_details {
+	class LMainWindowContentContext;
+}
+
+class LMainWindow : public QMainWindow {
+	Q_OBJECT
+public:
+
+	LMainWindow(QWidget *parent = nullptr);
+	~LMainWindow();
+
+	void initModuleMenus();
+	void setTabCaptionForWidget(QWidget *widget, const QString &caption, const QString &hint);
+	void setTabIcon(QWidget *widget, const QString &iconname);
+
+	/// Called when a newly created page is added to the QTabWidget
+	void addPage(PluginContentWidget* page, QString caption);
+
+	IPluginContentWidgetContext* context();
+protected:
+	QTabWidget *m_tabWidget = nullptr;
+	QToolBar *m_mainToolBar = nullptr;
+
+	// Standard menu's
+	QMenu *m_fileMenu = nullptr;
+
+	// Standard actions
+	QAction *m_closeAction = nullptr;
+
+
+	void addModuleMenuActions();
+
+	void addToolBarButtonsForPage(PluginContentWidget *page);
+	void removeToolBarButtonsForPage(PluginContentWidget *page);
+private:
+	LMainWindow_details::LMainWindowContentContext *m_context;
+	PluginContentWidget *m_previousPage = nullptr; ///< tracks which pages buttons were previously being displayed
+
+	void createActions();
+	void addMenuAction(const MenuAction &ma);
+
+private slots:
+	void actionClose_triggered();
+	void tabWidget_tabCloseRequested(int index);
+	void tabWidget_currentChanged(int index);
+};
+
+
+#endif // LMAINWINDOW_H