Emit DockRegistry::windowChangedScreen()

We now have a signal we can connect to adapt sizes to logical
dpi changes

src/MainWindow.cpp

@@ -18,15 +18,18 @@
 
 #include "MainWindow.h"
 #include "Config.h"
+#include "DockRegistry_p.h"
+#include "DropAreaWithCentralFrame_p.h"
 #include "DropArea_p.h"
 #include "Frame_p.h"
+#include "FrameworkWidgetFactory.h"
 #include "Logging_p.h"
 #include "SideBar_p.h"
-#include "DropAreaWithCentralFrame_p.h"
-#include "FrameworkWidgetFactory.h"
 
-#include <QVBoxLayout>
 #include <QPainter>
+#include <QScreen>
+#include <QVBoxLayout>
+#include <QWindow>
 
 // clazy:excludeall=ctor-missing-parent-argument,missing-qobject-macro
 
@@ -92,6 +95,10 @@ MainWindow::MainWindow(const QString &name, MainWindowOptions options,
     }
 
     setCentralWidget(centralWidget);
+
+    create();
+    connect(windowHandle(), &QWindow::screenChanged, DockRegistry::self(),
+            [this] { Q_EMIT DockRegistry::self()->windowChangedScreen(windowHandle()); });
 }
 
 MainWindow::~MainWindow()

src/private/DockRegistry_p.h

@@ -206,7 +206,11 @@ public:
     SideBarLocation sideBarLocationForDockWidget(const DockWidgetBase *) const;
 
     ///@brief Overload that returns the SideBar itself
-    SideBar* sideBarForDockWidget(const DockWidgetBase *) const;
+    SideBar *sideBarForDockWidget(const DockWidgetBase *) const;
+
+Q_SIGNALS:
+    /// @brief emitted when a main window or a floating window change screen
+    void windowChangedScreen(QWindow *);
 
 protected:
     bool eventFilter(QObject *watched, QEvent *event) override;

src/private/widgets/FloatingWindowWidget.cpp

@@ -9,15 +9,17 @@
   Contact KDAB at <info@kdab.com> for commercial licensing options.
 */
 
+#include "DockRegistry_p.h"
+#include "DropArea_p.h"
 #include "FloatingWindowWidget_p.h"
 #include "Logging_p.h"
-#include "Utils_p.h"
-#include "DropArea_p.h"
 #include "TitleBar_p.h"
+#include "Utils_p.h"
 
 #include <QApplication>
 #include <QPainter>
 #include <QVBoxLayout>
+#include <QWindow>
 #include <QWindowStateChangeEvent>
 
 using namespace KDDockWidgets;
@@ -56,7 +58,15 @@ void FloatingWindowWidget::paintEvent(QPaintEvent *ev)
 bool FloatingWindowWidget::event(QEvent *ev)
 {
     if (ev->type() == QEvent::WindowStateChange)
-        Q_EMIT windowStateChanged(static_cast<QWindowStateChangeEvent*>(ev));
+        Q_EMIT windowStateChanged(static_cast<QWindowStateChangeEvent *>(ev));
+
+    if (ev->type() == QEvent::Show && !m_screenChangedConnection) {
+        // We connect after QEvent::Show, so we have a QWindow. Qt doesn't offer much API to
+        // intercept screen events
+        m_screenChangedConnection =
+            connect(windowHandle(), &QWindow::screenChanged, DockRegistry::self(),
+                    [this] { Q_EMIT DockRegistry::self()->windowChangedScreen(windowHandle()); });
+    }
 
     return FloatingWindow::event(ev);
 }

src/private/widgets/FloatingWindowWidget_p.h

@@ -32,6 +32,7 @@ protected:
     bool event(QEvent *ev) override;
 
     QVBoxLayout *const m_vlayout;
+    QMetaObject::Connection m_screenChangedConnection;
 
 private:
     void init();