QPlatformSystemTrayIcon: Add signal contextMenuRequested()

Add a signal passing the global position of the context menu.
For platforms that do not provide native menus, QSystemTrayIcon
will show a QMenu based menu.

Change-Id: I799e4a84ca38e00ea33f3c842ea4ca43ecb8c83f
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/gui/kernel/qplatformsystemtrayicon.cpp

@@ -139,11 +139,20 @@ QPlatformSystemTrayIcon::~QPlatformSystemTrayIcon()
     Returns \c true if the system tray supports messages on the platform.
 */
 
+/*!
+    \fn void QPlatformSystemTrayIcon::contextMenuRequested(QPoint globalPos, const QPlatformScreen *screen)
+    This signal is emitted when the context menu is requested.
+    In particular, on platforms where createMenu() returns nullptr,
+    its emission will cause QSystemTrayIcon to show a QMenu-based menu.
+    \sa activated()
+    \since 5.10
+*/
+
 /*!
     \fn void QPlatformSystemTrayIcon::activated(QPlatformSystemTrayIcon::ActivationReason reason)
     This signal is emitted when the user activates the system tray icon.
     \a reason specifies the reason for activation.
-    \sa QSystemTrayIcon::ActivationReason
+    \sa QSystemTrayIcon::ActivationReason, contextMenuRequested()
 */
 
 /*!

src/gui/kernel/qplatformsystemtrayicon.h

@@ -49,6 +49,7 @@
 QT_BEGIN_NAMESPACE
 
 class QPlatformMenu;
+class QPlatformScreen;
 class QIcon;
 class QString;
 class QRect;
@@ -88,6 +89,7 @@ public:
 
 Q_SIGNALS:
     void activated(QPlatformSystemTrayIcon::ActivationReason reason);
+    void contextMenuRequested(QPoint globalPos, const QPlatformScreen *screen);
     void messageClicked();
 };
 

src/widgets/util/qsystemtrayicon.cpp

@@ -61,6 +61,9 @@
 #include "qdesktopwidget.h"
 #include "qbitmap.h"
 
+#include <private/qhighdpiscaling_p.h>
+#include <qpa/qplatformscreen.h>
+
 QT_BEGIN_NAMESPACE
 
 static QIcon messageIcon2qIcon(QSystemTrayIcon::MessageIcon icon)
@@ -196,8 +199,23 @@ QSystemTrayIcon::~QSystemTrayIcon()
 void QSystemTrayIcon::setContextMenu(QMenu *menu)
 {
     Q_D(QSystemTrayIcon);
+    QMenu *oldMenu = d->menu.data();
     d->menu = menu;
     d->updateMenu_sys();
+    if (oldMenu != menu && d->qpa_sys) {
+        // Show the QMenu-based menu for QPA plugins that do not provide native menus
+        if (oldMenu && !oldMenu->platformMenu())
+            QObject::disconnect(d->qpa_sys, &QPlatformSystemTrayIcon::contextMenuRequested, menu, nullptr);
+        if (menu && !menu->platformMenu()) {
+            QObject::connect(d->qpa_sys, &QPlatformSystemTrayIcon::contextMenuRequested,
+                             menu,
+                             [menu](QPoint globalNativePos, const QPlatformScreen *platformScreen)
+            {
+                QScreen *screen = platformScreen ? platformScreen->screen() : nullptr;
+                menu->popup(QHighDpi::fromNativePixels(globalNativePos, screen), nullptr);
+            });
+        }
+    }
 }
 
 /*!

src/widgets/util/qsystemtrayicon_win.cpp

@@ -334,6 +334,7 @@ bool QSystemTrayIconSys::winEvent( MSG *m, long *result )
 
 QSystemTrayIconPrivate::QSystemTrayIconPrivate()
     : sys(0),
+      qpa_sys(nullptr),
       visible(false)
 {
 }