QLineEdit: Add an inputRejected() signal for when a key is not allowed

[ChangeLog][QtWidgets][QLineEdit] Added inputRejected() signal for when
a key press is not accepted by the QLineEdit. For instance, when an
invalid key is pressed for a validator set.

Task-number: QTBUG-57448
Change-Id: I39182a78b07b37c6da01905b8da4c57930e3454b
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/widgets/qlineedit.cpp

@@ -1673,6 +1673,16 @@ void QLineEdit::mouseDoubleClickEvent(QMouseEvent* e)
     the inputMask() and the validator() returns QValidator::Acceptable.
 */
 
+/*!
+    \fn void QLineEdit::inputRejected()
+
+    This signal is emitted when the user presses a key that is not
+    considered to be acceptable input. For example, if a key press
+    results in a validator's validate() call to return Invalid.
+    Another case is when trying to enter in more characters beyond the
+    maximum length of the line edit.
+*/
+
 /*!
     Converts the given key press \a event into a line edit action.
 

src/widgets/widgets/qlineedit.h

@@ -207,6 +207,7 @@ Q_SIGNALS:
     void returnPressed();
     void editingFinished();
     void selectionChanged();
+    void inputRejected();
 
 protected:
     void mousePressEvent(QMouseEvent *) override;

src/widgets/widgets/qlineedit_p.cpp

@@ -214,6 +214,7 @@ void QLineEditPrivate::init(const QString& txt)
 
     QObject::connect(control, SIGNAL(updateNeeded(QRect)),
             q, SLOT(_q_updateNeeded(QRect)));
+    QObject::connect(control, SIGNAL(inputRejected()), q, SIGNAL(inputRejected()));
 
     QStyleOptionFrame opt;
     q->initStyleOption(&opt);

src/widgets/widgets/qwidgetlinecontrol.cpp

@@ -715,6 +715,8 @@ bool QWidgetLineControl::finishChange(int validateFromState, bool update, bool e
                     return true;
                 }
                 m_cursor = cursorCopy;
+            } else {
+                emit inputRejected();
             }
         }
 #endif
@@ -762,6 +764,8 @@ void QWidgetLineControl::internalSetText(const QString &txt, int pos, bool edite
     if (m_maskData) {
         m_text = maskString(0, txt, true);
         m_text += clearString(m_text.length(), m_maxLength - m_text.length());
+        if (edited && oldText == m_text)
+            emit inputRejected();
     } else {
         m_text = txt.isEmpty() ? txt : txt.left(m_maxLength);
     }
@@ -839,6 +843,8 @@ void QWidgetLineControl::internalInsert(const QString &s)
         addCommand(Command(SetSelection, m_cursor, 0, m_selstart, m_selend));
     if (m_maskData) {
         QString ms = maskString(m_cursor, s);
+        if (ms.isEmpty() && !s.isEmpty())
+            emit inputRejected();
 #ifndef QT_NO_ACCESSIBILITY
         QAccessibleTextInsertEvent insertEvent(accessibleObject(), m_cursor, ms);
         QAccessible::updateAccessibility(&insertEvent);
@@ -866,6 +872,8 @@ void QWidgetLineControl::internalInsert(const QString &s)
             for (int i = 0; i < (int) s.left(remaining).length(); ++i)
                addCommand(Command(Insert, m_cursor++, s.at(i), -1, -1));
             m_textDirty = true;
+        } else {
+            emit inputRejected();
         }
     }
 }

src/widgets/widgets/qwidgetlinecontrol_p.h

@@ -545,6 +545,7 @@ Q_SIGNALS:
     void accepted();
     void editingFinished();
     void updateNeeded(const QRect &);
+    void inputRejected();
 
 #ifdef QT_KEYPAD_NAVIGATION
     void editFocusChange(bool);

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

@@ -304,7 +304,7 @@ private slots:
     void QTBUG59957_clearButtonLeftmostAction();
     void QTBUG_60319_setInputMaskCheckImSurroundingText();
     void testQuickSelectionWithMouse();
-
+    void inputRejected();
 protected slots:
     void editingFinished();
 
@@ -4820,5 +4820,44 @@ void tst_QLineEdit::testQuickSelectionWithMouse()
     QVERIFY(lineEdit.selectedText().endsWith(suffix));
 }
 
+void tst_QLineEdit::inputRejected()
+{
+    QLineEdit *testWidget = ensureTestWidget();
+    QSignalSpy spyInputRejected(testWidget, SIGNAL(inputRejected()));
+
+    QTest::keyClicks(testWidget, "abcde");
+    QCOMPARE(spyInputRejected.count(), 0);
+    testWidget->setText("fghij");
+    QCOMPARE(spyInputRejected.count(), 0);
+    testWidget->insert("k");
+    QCOMPARE(spyInputRejected.count(), 0);
+
+    testWidget->clear();
+    testWidget->setMaxLength(5);
+    QTest::keyClicks(testWidget, "abcde");
+    QCOMPARE(spyInputRejected.count(), 0);
+    QTest::keyClicks(testWidget, "fgh");
+    QCOMPARE(spyInputRejected.count(), 3);
+
+    testWidget->setMaxLength(INT_MAX);
+    testWidget->clear();
+    spyInputRejected.clear();
+    QIntValidator intValidator(1, 100);
+    testWidget->setValidator(&intValidator);
+    QTest::keyClicks(testWidget, "11");
+    QCOMPARE(spyInputRejected.count(), 0);
+    QTest::keyClicks(testWidget, "a#");
+    QCOMPARE(spyInputRejected.count(), 2);
+
+    testWidget->clear();
+    testWidget->setValidator(0);
+    spyInputRejected.clear();
+    testWidget->setInputMask("999.999.999.999;_");
+    QTest::keyClicks(testWidget, "11");
+    QCOMPARE(spyInputRejected.count(), 0);
+    QTest::keyClicks(testWidget, "a#");
+    QCOMPARE(spyInputRejected.count(), 2);
+}
+
 QTEST_MAIN(tst_QLineEdit)
 #include "tst_qlineedit.moc"