QLineEdit: show the clear button if it gets enabled after setting a text

We were fetching "lastText" too late, and setting the opacity
of the clear button to 0.

Change-Id: I82c2aea7dab4af4424fb57e12f78d07a0374457e
Task-number: QTBUG-45518
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/widgets/widgets/qlineedit_p.cpp

@@ -440,6 +440,10 @@ QWidget *QLineEditPrivate::addAction(QAction *newAction, QAction *before, QLineE
     Q_Q(QLineEdit);
     if (!newAction)
         return 0;
+    if (!hasSideWidgets()) { // initial setup.
+        QObject::connect(q, SIGNAL(textChanged(QString)), q, SLOT(_q_textChanged(QString)));
+        lastTextSize = q->text().size();
+    }
     QWidget *w = 0;
     // Store flags about QWidgetAction here since removeAction() may be called from ~QAction,
     // in which a qobject_cast<> no longer works.
@@ -456,10 +460,6 @@ QWidget *QLineEditPrivate::addAction(QAction *newAction, QAction *before, QLineE
         toolButton->setDefaultAction(newAction);
         w = toolButton;
     }
-    if (!hasSideWidgets()) { // initial setup.
-        QObject::connect(q, SIGNAL(textChanged(QString)), q, SLOT(_q_textChanged(QString)));
-        lastTextSize = q->text().size();
-    }
     // If there is a 'before' action, it takes preference
     PositionIndexPair positionIndex = before ? findSideWidget(before) : PositionIndexPair(position, -1);
     SideWidgetEntryList &list = positionIndex.first == QLineEdit::TrailingPosition ? trailingSideWidgets : leadingSideWidgets;

src/widgets/widgets/qlineedit_p.h

@@ -65,7 +65,7 @@ QT_BEGIN_NAMESPACE
 
 // QLineEditIconButton: This is a simple helper class that represents clickable icons that fade in with text
 
-class QLineEditIconButton : public QToolButton
+class Q_AUTOTEST_EXPORT QLineEditIconButton : public QToolButton
 {
     Q_OBJECT
     Q_PROPERTY(qreal opacity READ opacity WRITE setOpacity)

tests/auto/widgets/widgets/qlineedit/tst_qlineedit.cpp

@@ -304,6 +304,7 @@ private slots:
     void undoRedoAndEchoModes();
 
     void clearButton();
+    void clearButtonVisibleAfterSettingText_QTBUG_45518();
     void sideWidgets();
 
     void shouldShowPlaceholderText_data();
@@ -4273,6 +4274,50 @@ void tst_QLineEdit::clearButton()
     QVERIFY(!clearButton->isEnabled());
 }
 
+void tst_QLineEdit::clearButtonVisibleAfterSettingText_QTBUG_45518()
+{
+#ifndef QT_BUILD_INTERNAL
+    QSKIP("This test requires a developer build");
+#else
+    QLineEdit edit;
+    edit.setMinimumWidth(200);
+    centerOnScreen(&edit);
+    QLineEditIconButton *clearButton;
+    clearButton = edit.findChild<QLineEditIconButton *>();
+    QVERIFY(!clearButton);
+
+    edit.setText(QStringLiteral("some text"));
+    edit.show();
+    QVERIFY(QTest::qWaitForWindowActive(&edit));
+
+    QVERIFY(!edit.isClearButtonEnabled());
+
+    clearButton = edit.findChild<QLineEditIconButton *>();
+    QVERIFY(!clearButton);
+
+    edit.setClearButtonEnabled(true);
+    QVERIFY(edit.isClearButtonEnabled());
+
+    clearButton = edit.findChild<QLineEditIconButton *>();
+    QVERIFY(clearButton);
+    QVERIFY(clearButton->isVisible());
+
+    QTRY_VERIFY(clearButton->opacity() > 0);
+    QTRY_COMPARE(clearButton->cursor().shape(), Qt::ArrowCursor);
+
+    QTest::mouseClick(clearButton, Qt::LeftButton, 0, clearButton->rect().center());
+    QTRY_COMPARE(edit.text(), QString());
+
+    QTRY_COMPARE(clearButton->opacity(), qreal(0));
+    QTRY_COMPARE(clearButton->cursor().shape(), clearButton->parentWidget()->cursor().shape());
+
+    edit.setClearButtonEnabled(false);
+    QVERIFY(!edit.isClearButtonEnabled());
+    clearButton = edit.findChild<QLineEditIconButton *>();
+    QVERIFY(!clearButton);
+#endif // QT_BUILD_INTERNAL
+}
+
 void tst_QLineEdit::sideWidgets()
 {
     QWidget testWidget;