Fix wrong initial position

If the widget is larger than the screen,
its title bar top left corner will be shown
inside the screen.

Task-number: QTBUG-30142

Change-Id: Id93773874be3616b3ef4b9bee6e1bb751c541d7b
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

3 files changed, 41 insertions, 1 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoahelpers.mm b/src/plugins/platforms/cocoa/qcocoahelpers.mm
index 3f00893465..5ec2cea362 100644
--- a/src/plugins/platforms/cocoa/qcocoahelpers.mm
+++ b/src/plugins/platforms/cocoa/qcocoahelpers.mm
@@ -47,6 +47,7 @@
 #include <QtGui>
 #include <qpa/qplatformscreen.h>
 #include <private/qguiapplication_p.h>
+#include <private/qwindow_p.h>
 
 #ifndef QT_NO_WIDGETS
 #include <QtWidgets/QWidget>
@@ -584,10 +585,28 @@ QString qt_mac_applicationName()
     return appName;
 }
 
+/*
+    Mac window coordinates are in the first quadrant: 0, 0 is at the lower-left
+    corner of the primary screen. This function converts the given rect to an
+    NSRect for the window geometry, flipping from 4th quadrant to 1st quadrant
+    and simultaneously ensuring that as much of the window as possible will be
+    onscreen. If the rect is too tall for the screen, the OS will reduce the
+    window's height anyway; but by moving the window upwards we can have more
+    of it onscreen.  But the application can still control the y coordinate
+    in case it really wants the window to be positioned partially offscreen.
+*/
 NSRect qt_mac_flipRect(const QRect &rect, QWindow *window)
 {
     QPlatformScreen *onScreen = QPlatformScreen::platformScreenForWindow(window);
-    int flippedY = onScreen->geometry().height() - rect.y() - rect.height();
+    int flippedY = onScreen->geometry().height() - (rect.y() + rect.height());
+
+    // In case of automatic positioning, try to put as much of the window onscreen as possible.
+    if (window->isTopLevel() && qt_window_private(const_cast<QWindow*>(window))->positionAutomatic && flippedY < 0)
+        flippedY = onScreen->geometry().height() - onScreen->availableGeometry().height() - onScreen->availableGeometry().y();
+#ifdef QT_COCOA_ENABLE_WINDOW_DEBUG
+    qDebug() << Q_FUNC_INFO << rect << "flippedY" << flippedY <<
+                "screen" << onScreen->geometry() << "available" << onScreen->availableGeometry();
+#endif
     return NSMakeRect(rect.x(), flippedY, rect.width(), rect.height());
 }
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 2da0af8abb..6cbe3e8cf7 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -487,6 +487,11 @@ QWindowsWindow::WindowData
     const QWindowCreationContextPtr context(new QWindowCreationContext(w, rect, data.customMargins, style, exStyle));
     QWindowsContext::instance()->setWindowCreationContext(context);
 
+    if (context->frameX < 0)
+        context->frameX = 0;
+    if (context->frameY < 0)
+        context->frameY = 0;
+
     if (QWindowsContext::verboseWindows)
         qDebug().nospace()
                 << "CreateWindowEx: " << w << *this
diff --git a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
index e6b1caf694..3d7cc14a5d 100644
--- a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
+++ b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
@@ -412,6 +412,7 @@ private slots:
 
     void keyboardModifiers();
     void mouseDoubleClickBubbling_QTBUG29680();
+    void largerThanScreen_QTBUG30142();
 
 private:
     bool ensureScreenSize(int width, int height);
@@ -10074,5 +10075,20 @@ void tst_QWidget::mouseDoubleClickBubbling_QTBUG29680()
     QTRY_VERIFY(parent.triggered);
 }
 
+void tst_QWidget::largerThanScreen_QTBUG30142()
+{
+    QWidget widget;
+    widget.resize(200, 4000);
+    widget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget));
+    QVERIFY(widget.frameGeometry().y() >= 0);
+
+    QWidget widget2;
+    widget2.resize(10000, 400);
+    widget2.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget2));
+    QVERIFY(widget2.frameGeometry().x() >= 0);
+}
+
 QTEST_MAIN(tst_QWidget)
 #include "tst_qwidget.moc"