Deprecate QGuiApplication::fontChanged() signal

Rather than have a fontChanged() signal which can be connected to for
tracking when the application font has changed, then it is better to
use the event that is sent to all windows and the application itself.
That way it is easy for a window/widget or item that cares about the
change to the application font to catch it in the event() function.

[ChangeLog][QtGui][QGuiApplication] Deprecated fontChanged() signal in
favor of QEvent::ApplicationFontChanged.

Change-Id: Iae8e832238fc85e385a52305bc04f16e597454b0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 12 insertions, 2 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 1d71c6d075..8e50cbc469 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1900,6 +1900,11 @@ bool QGuiApplication::event(QEvent *e)
             if (topLevelWindow->flags() != Qt::Desktop)
                 postEvent(topLevelWindow, new QEvent(QEvent::LanguageChange));
         }
+    } else if (e->type() == QEvent::ApplicationFontChange) {
+        for (auto *topLevelWindow : QGuiApplication::topLevelWindows()) {
+            if (topLevelWindow->flags() != Qt::Desktop)
+                postEvent(topLevelWindow, new QEvent(QEvent::ApplicationFontChange));
+        }
     } else if (e->type() == QEvent::Quit) {
         // Close open windows. This is done in order to deliver de-expose
         // events while the event loop is still running.
@@ -3408,8 +3413,10 @@ void QGuiApplicationPrivate::applyWindowGeometrySpecificationTo(QWindow *window)
 /*!
     \since 5.11
     \fn void QGuiApplication::fontChanged(const QFont &font)
+    \obsolete
 
-    This signal is emitted when the \a font of the application changes.
+    This signal is emitted when the \a font of the application changes. Use
+    QEvent::ApplicationFontChanged instead.
 
     \sa font()
 */
@@ -3450,6 +3457,8 @@ void QGuiApplication::setFont(const QFont &font)
         auto font = *QGuiApplicationPrivate::app_font;
         locker.unlock();
         emit qGuiApp->fontChanged(font);
+        QEvent event(QEvent::ApplicationFontChange);
+        QGuiApplication::sendEvent(qGuiApp, &event);
     }
 }
 
diff --git a/src/gui/kernel/qguiapplication.h b/src/gui/kernel/qguiapplication.h
index fc74c5299a..0c642d8ff5 100644
--- a/src/gui/kernel/qguiapplication.h
+++ b/src/gui/kernel/qguiapplication.h
@@ -190,8 +190,9 @@ Q_SIGNALS:
 #endif
     void paletteChanged(const QPalette &pal);
     void applicationDisplayNameChanged();
+#if QT_DEPRECATED_SINCE(6, 0)
     void fontChanged(const QFont &font);
-
+#endif
 protected:
     bool event(QEvent *) override;
     bool compressEvent(QEvent *, QObject *receiver, QPostEventList *) override;