Fix delayed password masking mid-string.

Unmask the last character typed, not the last character in the string.

Change-Id: I9c70d2347bf878c18ab0a7f4ea76f755ca19a85c
Task-number: QTBUG-17003
Reviewed-by: Alan Alpert
(cherry picked from commit b98e9e69dd8ba33d5f01b9518d95b63b86c4b443)

Reapplied after bad v4.7.4 merge

2 files changed, 10 insertions, 3 deletions

diff --git a/src/gui/widgets/qlinecontrol.cpp b/src/gui/widgets/qlinecontrol.cpp
index a879b49..198bc04 100644
--- a/src/gui/widgets/qlinecontrol.cpp
+++ b/src/gui/widgets/qlinecontrol.cpp
@@ -60,7 +60,7 @@
 QT_BEGIN_NAMESPACE
 
 #ifdef QT_GUI_PASSWORD_ECHO_DELAY
-static int qt_passwordEchoDelay = QT_GUI_PASSWORD_ECHO_DELAY;
+static const int qt_passwordEchoDelay = QT_GUI_PASSWORD_ECHO_DELAY;
 #endif
 
 /*!
@@ -93,8 +93,8 @@ void QLineControl::updateDisplayText(bool forceUpdate)
     if (m_echoMode == QLineEdit::Password) {
         str.fill(m_passwordCharacter);
 #ifdef QT_GUI_PASSWORD_ECHO_DELAY
-        if (m_passwordEchoTimer != 0 && !str.isEmpty()) {
-            int cursor = m_text.length() - 1;
+        if (m_passwordEchoTimer != 0 && m_cursor > 0 && m_cursor <= m_text.length()) {
+            int cursor = m_cursor - 1;
             QChar uc = m_text.at(cursor);
             str[cursor] = uc;
             if (cursor > 0 && uc.unicode() >= 0xdc00 && uc.unicode() < 0xe000) {
diff --git a/tests/auto/qlineedit/tst_qlineedit.cpp b/tests/auto/qlineedit/tst_qlineedit.cpp
index 1f33458..3276375 100644
--- a/tests/auto/qlineedit/tst_qlineedit.cpp
+++ b/tests/auto/qlineedit/tst_qlineedit.cpp
@@ -1764,6 +1764,13 @@ void tst_QLineEdit::passwordEchoDelay()
     QApplication::sendEvent(testWidget, &ev);
     QCOMPARE(testWidget->displayText(), QString(7, fillChar) + QLatin1Char('7'));
 
+    testWidget->setCursorPosition(3);
+    QCOMPARE(testWidget->displayText(), QString(7, fillChar) + QLatin1Char('7'));
+    QTest::keyPress(testWidget, 'a');
+    QCOMPARE(testWidget->displayText(), QString(3, fillChar) + QLatin1Char('a') + QString(5, fillChar));
+    QTest::keyPress(testWidget, Qt::Key_Backspace);
+    QCOMPARE(testWidget->displayText(), QString(8, fillChar));
+
     // restore clean state
     testWidget->setEchoMode(QLineEdit::Normal);
 }