Delay masking the last character in Password echo mode.

If QT_GUI_PASSWORD_ECHO_DELAY is defined in qplatformdefs.h with an
integer value in milliseconds, QLineEdit and TextInput will display
the last character entered unmasked for that delay period and then
mask the character as normal.  If QT_GUI_PASSWORD_ECHO_DELAY is
not defined then the behaviour is unchanged.

Change-Id: I55f527932d34453828caba88e93ad57e012e79be
Task-number: QTBUG-17003
Reviewed-by: Martin Jones

2 files changed, 77 insertions, 3 deletions

diff --git a/src/gui/widgets/qlinecontrol.cpp b/src/gui/widgets/qlinecontrol.cpp
index 1432f24..a879b49 100644
--- a/src/gui/widgets/qlinecontrol.cpp
+++ b/src/gui/widgets/qlinecontrol.cpp
@@ -59,6 +59,22 @@
 
 QT_BEGIN_NAMESPACE
 
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+static int qt_passwordEchoDelay = QT_GUI_PASSWORD_ECHO_DELAY;
+#endif
+
+/*!
+    \macro QT_GUI_PASSWORD_ECHO_DELAY
+
+    \internal
+
+    Defines the amount of time in milliseconds the last entered character
+    should be displayed unmasked in the Password echo mode.
+
+    If not defined in qplatformdefs.h there will be no delay in masking
+    password characters.
+*/
+
 /*!
     \internal
 
@@ -74,9 +90,25 @@ void QLineControl::updateDisplayText(bool forceUpdate)
     else
         str = m_text;
 
-    if (m_echoMode == QLineEdit::Password || (m_echoMode == QLineEdit::PasswordEchoOnEdit
-                && !m_passwordEchoEditing))
+    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;
+            QChar uc = m_text.at(cursor);
+            str[cursor] = uc;
+            if (cursor > 0 && uc.unicode() >= 0xdc00 && uc.unicode() < 0xe000) {
+                // second half of a surrogate, check if we have the first half as well,
+                // if yes restore both at once
+                uc = m_text.at(cursor - 1);
+                if (uc.unicode() >= 0xd800 && uc.unicode() < 0xdc00)
+                    str[cursor - 1] = uc;
+            }
+        }
+#endif
+    } else if (m_echoMode == QLineEdit::PasswordEchoOnEdit && !m_passwordEchoEditing) {
+        str.fill(m_passwordCharacter);
+    }
 
     // replace certain non-printable characters with spaces (to avoid
     // drawing boxes when using fonts that don't have glyphs for such
@@ -311,6 +343,7 @@ void QLineControl::init(const QString &txt)
 */
 void QLineControl::updatePasswordEchoEditing(bool editing)
 {
+    cancelPasswordEchoTimer();
     m_passwordEchoEditing = editing;
     updateDisplayText();
 }
@@ -640,6 +673,7 @@ bool QLineControl::finishChange(int validateFromState, bool update, bool edited)
 */
 void QLineControl::internalSetText(const QString &txt, int pos, bool edited)
 {
+    cancelPasswordEchoTimer();
     internalDeselect();
     emit resetInputContext();
     QString oldText = m_text;
@@ -687,6 +721,13 @@ void QLineControl::addCommand(const Command &cmd)
 */
 void QLineControl::internalInsert(const QString &s)
 {
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+    if (m_echoMode == QLineEdit::Password) {
+        if (m_passwordEchoTimer != 0)
+            killTimer(m_passwordEchoTimer);
+        m_passwordEchoTimer = startTimer(qt_passwordEchoDelay);
+    }
+#endif
     if (hasSelectedText())
         addCommand(Command(SetSelection, m_cursor, 0, m_selstart, m_selend));
     if (m_maskData) {
@@ -724,6 +765,7 @@ void QLineControl::internalInsert(const QString &s)
 void QLineControl::internalDelete(bool wasBackspace)
 {
     if (m_cursor < (int) m_text.length()) {
+        cancelPasswordEchoTimer();
         if (hasSelectedText())
             addCommand(Command(SetSelection, m_cursor, 0, m_selstart, m_selend));
         addCommand(Command((CommandType)((m_maskData ? 2 : 0) + (wasBackspace ? Remove : Delete)),
@@ -750,6 +792,7 @@ void QLineControl::internalDelete(bool wasBackspace)
 void QLineControl::removeSelectedText()
 {
     if (m_selstart < m_selend && m_selend <= (int) m_text.length()) {
+        cancelPasswordEchoTimer();
         separate();
         int i ;
         addCommand(Command(SetSelection, m_cursor, 0, m_selstart, m_selend));
@@ -1148,6 +1191,7 @@ void QLineControl::internalUndo(int until)
 {
     if (!isUndoAvailable())
         return;
+    cancelPasswordEchoTimer();
     internalDeselect();
     while (m_undoState && m_undoState > until) {
         Command& cmd = m_history[--m_undoState];
@@ -1349,6 +1393,12 @@ void QLineControl::timerEvent(QTimerEvent *event)
     } else if (event->timerId() == m_tripleClickTimer) {
         killTimer(m_tripleClickTimer);
         m_tripleClickTimer = 0;
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+    } else if (event->timerId() == m_passwordEchoTimer) {
+        killTimer(m_passwordEchoTimer);
+        m_passwordEchoTimer = 0;
+        updateDisplayText();
+#endif
     }
 }
 
diff --git a/src/gui/widgets/qlinecontrol_p.h b/src/gui/widgets/qlinecontrol_p.h
index e318b0a..0ab454b 100644
--- a/src/gui/widgets/qlinecontrol_p.h
+++ b/src/gui/widgets/qlinecontrol_p.h
@@ -66,6 +66,8 @@
 #include "QtCore/qpoint.h"
 #include "QtGui/qcompleter.h"
 
+#include "qplatformdefs.h"
+
 QT_BEGIN_HEADER
 
 QT_BEGIN_NAMESPACE
@@ -85,6 +87,9 @@ public:
         m_ascent(0), m_maxLength(32767), m_lastCursorPos(-1),
         m_tripleClickTimer(0), m_maskData(0), m_modifiedState(0), m_undoState(0),
         m_selstart(0), m_selend(0), m_passwordEchoEditing(false)
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+        , m_passwordEchoTimer(0)
+#endif
     {
         init(txt);
     }
@@ -218,6 +223,7 @@ public:
     uint echoMode() const { return m_echoMode; }
     void setEchoMode(uint mode)
     {
+        cancelPasswordEchoTimer();
         m_echoMode = mode;
         m_passwordEchoEditing = false;
         updateDisplayText();
@@ -267,7 +273,13 @@ public:
     QString preeditAreaText() const { return m_textLayout.preeditAreaText(); }
 
     void updatePasswordEchoEditing(bool editing);
-    bool passwordEchoEditing() const { return m_passwordEchoEditing; }
+    bool passwordEchoEditing() const {
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+        if (m_passwordEchoTimer != 0)
+            return true;
+#endif
+        return m_passwordEchoEditing ;
+    }
 
     QChar passwordCharacter() const { return m_passwordCharacter; }
     void setPasswordCharacter(const QChar &character) { m_passwordCharacter = character; updateDisplayText(); }
@@ -415,6 +427,18 @@ private:
 
     bool m_passwordEchoEditing;
     QChar m_passwordCharacter;
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+    int m_passwordEchoTimer;
+#endif
+    void cancelPasswordEchoTimer()
+    {
+#ifdef QT_GUI_PASSWORD_ECHO_DELAY
+        if (m_passwordEchoTimer != 0) {
+            killTimer(m_passwordEchoTimer);
+            m_passwordEchoTimer = 0;
+        }
+#endif
+    }
 
 Q_SIGNALS:
     void cursorPositionChanged(int, int);