Add ReadOnlyChange event to widgets that support setReadOnly(bool).

This is useful for widget styles to react when widgets are set
read-only, e.g. to update their palette accordingly.

[ChangeLog][QtWidgets] All widgets with a setReadOnly method now
send a ReadOnlyChange event (e.g. for app-specific palette changes)

Change-Id: I74719a3e1b7d034d9bfc94305f846f42aae935bd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qcoreevent.cpp

@@ -192,6 +192,7 @@ QT_BEGIN_NAMESPACE
     \value Polish                           The widget is polished.
     \value PolishRequest                    The widget should be polished.
     \value QueryWhatsThis                   The widget should accept the event if it has "What's This?" help.
+    \value ReadOnlyChange                   Widget's read-only state has changed (since Qt 5.4).
     \value RequestSoftwareInputPanel        A widget wants to open a software input panel (SIP).
     \value Resize                           Widget's size changed (QResizeEvent).
     \value ScrollPrepare                    The object needs to fill in its geometry information (QScrollPrepareEvent).

src/corelib/kernel/qcoreevent.h

@@ -150,6 +150,8 @@ public:
         WindowUnblocked = 104,                  // windows modal blocking has ended
         WindowStateChange = 105,
 
+        ReadOnlyChange = 106,                   // readonly state has changed
+
         ToolTip = 110,
         WhatsThis = 111,
         StatusTip = 112,

src/widgets/kernel/qwidget.cpp

@@ -8224,6 +8224,7 @@ bool QWidget::event(QEvent *event)
     case QEvent::MacSizeChange:
     case QEvent::ContentsRectChange:
     case QEvent::ThemeChange:
+    case QEvent::ReadOnlyChange:
         changeEvent(event);
         break;
 
@@ -8395,7 +8396,7 @@ bool QWidget::event(QEvent *event)
   QEvent::ModifiedChange, QEvent::MouseTrackingChange,
   QEvent::ParentChange, QEvent::WindowStateChange,
   QEvent::LanguageChange, QEvent::LocaleChange,
-  QEvent::LayoutDirectionChange.
+  QEvent::LayoutDirectionChange, QEvent::ReadOnlyChange.
 
 */
 void QWidget::changeEvent(QEvent * event)

src/widgets/widgets/qabstractspinbox.cpp

@@ -315,6 +315,8 @@ void QAbstractSpinBox::setReadOnly(bool enable)
     Q_D(QAbstractSpinBox);
     d->readOnly = enable;
     d->edit->setReadOnly(enable);
+    QEvent event(QEvent::ReadOnlyChange);
+    QApplication::sendEvent(this, &event);
     update();
 }
 

src/widgets/widgets/qlineedit.cpp

@@ -1348,6 +1348,8 @@ void QLineEdit::setReadOnly(bool enable)
 #ifndef QT_NO_CURSOR
         setCursor(enable ? Qt::ArrowCursor : Qt::IBeamCursor);
 #endif
+        QEvent event(QEvent::ReadOnlyChange);
+        QCoreApplication::sendEvent(this, &event);
         update();
     }
 }

src/widgets/widgets/qplaintextedit.cpp

@@ -2529,6 +2529,8 @@ void QPlainTextEdit::setReadOnly(bool ro)
     }
     setAttribute(Qt::WA_InputMethodEnabled, shouldEnableInputMethod(this));
     d->control->setTextInteractionFlags(flags);
+    QEvent event(QEvent::ReadOnlyChange);
+    QApplication::sendEvent(this, &event);
 }
 
 /*!

src/widgets/widgets/qtextedit.cpp

@@ -2122,6 +2122,8 @@ void QTextEdit::setReadOnly(bool ro)
     }
     d->control->setTextInteractionFlags(flags);
     setAttribute(Qt::WA_InputMethodEnabled, shouldEnableInputMethod(this));
+    QEvent event(QEvent::ReadOnlyChange);
+    QApplication::sendEvent(this, &event);
 }
 
 /*!

tests/auto/widgets/widgets/qspinbox/tst_qspinbox.cpp

@@ -393,18 +393,31 @@ void tst_QSpinBox::valueChangedHelper(int value)
     actualValues << value;
 }
 
+class MySpinBox: public QSpinBox
+{
+public:
+    MySpinBox(QWidget *parent = 0) : QSpinBox(parent) {}
+
+    void changeEvent(QEvent *ev) {
+        eventsReceived.append(ev->type());
+    }
+    QList<QEvent::Type> eventsReceived;
+};
+
 void tst_QSpinBox::setReadOnly()
 {
-    QSpinBox spin(0);
+    MySpinBox spin(0);
     spin.show();
     QTest::keyClick(&spin, Qt::Key_Up);
     QCOMPARE(spin.value(), 1);
     spin.setReadOnly(true);
+    QCOMPARE(spin.eventsReceived, QList<QEvent::Type>() << QEvent::ReadOnlyChange);
     QTest::keyClick(&spin, Qt::Key_Up);
     QCOMPARE(spin.value(), 1);
     spin.stepBy(1);
     QCOMPARE(spin.value(), 2);
     spin.setReadOnly(false);
+    QCOMPARE(spin.eventsReceived, QList<QEvent::Type>() << QEvent::ReadOnlyChange << QEvent::ReadOnlyChange);
     QTest::keyClick(&spin, Qt::Key_Up);
     QCOMPARE(spin.value(), 3);
 }