WindowsQPA: Add default icon to custom titlebar

In case that no application icon was provided, use the IDI_APPLICATION
icon when Qt::WindowTitleHint was provided.

Fixes: QTBUG-133941
Pick-to: 6.9
Change-Id: Ifb479a7056e0841215d525c2346938bda31fc1c6
Reviewed-by: Tor Arne Vestbø <[email protected]>
Reviewed-by: Oliver Wolff <[email protected]>

1 files changed, 13 insertions, 8 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index fba0c620745..77e0cbfcaa6 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -3516,9 +3516,8 @@ void QWindowsWindow::updateCustomTitlebar()
     p.setPen(Qt::NoPen);
     if (!wnd->flags().testFlags(Qt::NoTitleBarBackgroundHint)) {
         QRect titleRect;
-        titleRect.setY(1);
         titleRect.setX(2);
-        titleRect.setWidth(windowWidth - 2);
+        titleRect.setWidth(windowWidth);
         titleRect.setHeight(titleBarHeight);
 
         if (isWindows11orAbove) {
@@ -3545,13 +3544,19 @@ void QWindowsWindow::updateCustomTitlebar()
         titleRect.setWidth(windowWidth);
         titleRect.setHeight(titleBarHeight);
 
-        const QIcon icon = wnd->icon();
-        if (!icon.isNull()) {
-            titleRect.adjust(factor * 4, 0, 0, 0);
-            QRect iconRect(titleRect.x(), titleRect.y() + factor * 8, factor * 16, factor * 16);
-            icon.paint(&p, iconRect);
-            titleRect.adjust(factor * 24, 0, 0, 0);
+        titleRect.adjust(factor * 4, 0, 0, 0);
+        QRect iconRect(titleRect.x(), titleRect.y() + factor * 8, factor * 16, factor * 16);
+        if (wnd->icon().isNull()) {
+            static QIcon defaultIcon;
+            if (defaultIcon.isNull()) {
+                const QImage defaultIconImage = QImage::fromHICON(LoadIcon(0, IDI_APPLICATION));
+                defaultIcon =  QIcon(QPixmap::fromImage(defaultIconImage));
+            }
+            defaultIcon.paint(&p, iconRect);
+        } else {
+            wnd->icon().paint(&p, iconRect);
         }
+        titleRect.adjust(factor * 24, 0, 0, 0);
 
         p.setPen(textPen);
         QFont titleFont = QWindowsIntegration::instance()->fontDatabase()->defaultFont();