Implement QWindowContainer::minimumSizeHint()

It will return the minimumSize of the underlying QWindow.
The container can then be put inside QLayouts without risking to be
shrunk to a smaller size than the QWindow::minimumSize.
Whenever the QWindow::minimumWidth or QWindow::minimumHeight changes, we call QWindowContainer::updateGeometry(), which will make the layout re-query QWindowContainer::minimumSizeHint() again.

Task-number: QTBUG-121798
Change-Id: Ib7ece7d9d75f2e4964ca9042d8d8b95ce3b17739
Reviewed-by: Doris Verria <doris.verria@qt.io>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

3 files changed, 33 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwindowcontainer.cpp b/src/widgets/kernel/qwindowcontainer.cpp
index cfd785a82c..c15ec54f35 100644
--- a/src/widgets/kernel/qwindowcontainer.cpp
+++ b/src/widgets/kernel/qwindowcontainer.cpp
@@ -221,6 +221,9 @@ QWindowContainer::QWindowContainer(QWindow *embeddedWindow, QWidget *parent, Qt:
 
     connect(qGuiApp, &QGuiApplication::focusWindowChanged,
             this, &QWindowContainer::focusWindowChanged);
+
+    connect(containedWindow(), &QWindow::minimumHeightChanged, this, &QWindowContainer::updateGeometry);
+    connect(containedWindow(), &QWindow::minimumWidthChanged, this, &QWindowContainer::updateGeometry);
 }
 
 QWindow *QWindowContainer::containedWindow() const
@@ -373,6 +376,11 @@ bool QWindowContainer::event(QEvent *e)
     return QWidget::event(e);
 }
 
+QSize QWindowContainer::minimumSizeHint() const
+{
+    return containedWindow() ? containedWindow()->minimumSize() : QSize(0, 0);
+}
+
 typedef void (*qwindowcontainer_traverse_callback)(QWidget *parent);
 static void qwindowcontainer_traverse(QWidget *parent, qwindowcontainer_traverse_callback callback)
 {
diff --git a/src/widgets/kernel/qwindowcontainer_p.h b/src/widgets/kernel/qwindowcontainer_p.h
index 8dc5c64af4..a303f25424 100644
--- a/src/widgets/kernel/qwindowcontainer_p.h
+++ b/src/widgets/kernel/qwindowcontainer_p.h
@@ -31,6 +31,7 @@ public:
     explicit QWindowContainer(QWindow *embeddedWindow, QWidget *parent = nullptr, Qt::WindowFlags f = { });
     ~QWindowContainer();
     QWindow *containedWindow() const;
+    QSize minimumSizeHint() const override;
 
     static void toplevelAboutToBeDestroyed(QWidget *parent);
     static void parentWasChanged(QWidget *parent);
diff --git a/tests/auto/widgets/kernel/qwindowcontainer/tst_qwindowcontainer.cpp b/tests/auto/widgets/kernel/qwindowcontainer/tst_qwindowcontainer.cpp
index ec79c48e1c..e620c5e79a 100644
--- a/tests/auto/widgets/kernel/qwindowcontainer/tst_qwindowcontainer.cpp
+++ b/tests/auto/widgets/kernel/qwindowcontainer/tst_qwindowcontainer.cpp
@@ -13,6 +13,7 @@
 #include <qscreen.h>
 #include <qscopedpointer.h>
 #include <qevent.h>
+#include <qboxlayout.h>
 
 
 class Window : public QWindow
@@ -46,6 +47,7 @@ public:
 private slots:
     void testShow();
     void testPositionAndSize();
+    void testSizeHints();
     void testExposeObscure();
     void testOwnership();
     void testBehindTheScenesDeletion();
@@ -109,7 +111,29 @@ void tst_QWindowContainer::testPositionAndSize()
     QCOMPARE(window->height(), container->height());
 }
 
+void tst_QWindowContainer::testSizeHints()
+{
+    QScopedPointer<QWidget> tlw(new QWidget);
+    QWindow *window = new QWindow();
+    window->setMinimumSize(QSize(200, 200));
+    window->setGeometry(m_availableGeometry.x() + 300, m_availableGeometry.y() + 400, 500, 600);
 
+    QScopedPointer<QWidget> container(QWidget::createWindowContainer(window));
+    container->setWindowTitle(QTest::currentTestFunction());
+
+    QVBoxLayout *vbox = new QVBoxLayout(tlw.data());
+    vbox->addWidget(container.data());
+    vbox->setContentsMargins(0, 0, 0, 0);
+
+    // Size hints should work regardless of visibility
+    QCOMPARE(container->minimumSizeHint(), window->minimumSize());
+    QCOMPARE(vbox->minimumSize(), window->minimumSize());
+
+    // Respect dynamic updates
+    window->setMinimumSize(QSize(210, 210));
+    QCOMPARE(container->minimumSizeHint(), window->minimumSize());
+    QCOMPARE(vbox->minimumSize(), window->minimumSize());
+}
 
 void tst_QWindowContainer::testExposeObscure()
 {