windowflags: Make it easier to debug windows without a frame

Without any content it was hard to see the window. Put some lipstick on it.

Change-Id: I0fefffb0a4deba7ac91e67a6153a9a27308fe493
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

tests/manual/windowflags/controllerwindow.cpp

@@ -59,7 +59,7 @@ ControllerWidget::ControllerWidget(QWidget *parent)
     QLabel *label = new QLabel(tr("Parent window"));
     parentWindow->setCentralWidget(label);
 
-    previewWindow = new QWindow;
+    previewWindow = new PreviewWindow;
     previewWindow->installEventFilter(this);
     previewWidget = new PreviewWidget;
     previewWidget->installEventFilter(this);

tests/manual/windowflags/previewwindow.cpp

@@ -32,9 +32,20 @@
 #include <QVBoxLayout>
 #include <QTextStream>
 #include <QTimer>
+#include <QPainter>
+#include <QLinearGradient>
 
 #include "previewwindow.h"
 
+void PreviewWindow::paintEvent(QPaintEvent *event)
+{
+    QPainter painter(this);
+    QLinearGradient gradient(0, 0, width(), height());
+    gradient.setColorAt(0, QColor("#64b3f4"));
+    gradient.setColorAt(1, QColor("#c2e59c"));
+    painter.fillRect(QRect(0, 0, width(), height()), gradient);
+}
+
 static void formatWindowFlags(QTextStream &str, Qt::WindowFlags flags)
 {
     str << "Window flags: " << hex << showbase << unsigned(flags) << noshowbase << dec << ' ';

tests/manual/windowflags/previewwindow.h

@@ -30,11 +30,17 @@
 #define PREVIEWWINDOW_H
 
 #include <QDialog>
+#include <QRasterWindow>
 
 QT_BEGIN_NAMESPACE
 class QPlainTextEdit;
 QT_END_NAMESPACE
 
+class PreviewWindow : public QRasterWindow
+{
+    void paintEvent(QPaintEvent *event);
+};
+
 class PreviewWidget : public QWidget
 {
     Q_OBJECT