Support visual cursor movement for BIDI text

Bidi input can in some contexts be more intuitive if the cursor
works in visual way: pressing left arrow key always make cursor
move one character to the left regardless the language of text,
pressing right arrow key always make cursor move to the right.
It is also the behavior of Mac OS X. Based on the above reason
and requests from Symbian we implemented this support for visual
movement in BIDI text. 3 public properties are added to
QTextDocument, QTextLayout and QLineEdit respectively:

- QTextDocument::defaultCursorMoveStyle can be used to control
  the cursor behavior in all widgets based on QTextDocument,
  like QTextEdit, QPlainTextEdit, etc. When set to QTextCursor::
  Visual, it will enable visual movement for all the cursors in
  the corresponding text edit. Default is QTextCursor::Logical.

- QTextLayout::cursorMoveStyle is used for low-level cursor
  manipulation. When set to Visual, it will enable visual movement
  behavior for all the cursor related methods, including cursorToX,
  xToCursor and drawCursor. Default is Logical.

- QLineEdit::cursorMoveStyle is used to control cursor movement
  behavior in QLineEdit. Default is Logical.:

Task-number: QTBUG-13859
Reviewed-by: Eskil
(cherry picked from commit c480dd641f5d22d1ee72cb27bf39e24c6df65658)

4 files changed, 43 insertions, 6 deletions

diff --git a/src/gui/widgets/qlinecontrol.cpp b/src/gui/widgets/qlinecontrol.cpp
index 289faa9b02..eb4e142328 100644
--- a/src/gui/widgets/qlinecontrol.cpp
+++ b/src/gui/widgets/qlinecontrol.cpp
@@ -1585,6 +1585,7 @@ void QLineControl::processKeyEvent(QKeyEvent* event)
     }
 
     bool unknown = false;
+    bool visual = cursorMoveStyle() == QTextCursor::Visual;
 
     if (false) {
     }
@@ -1649,11 +1650,11 @@ void QLineControl::processKeyEvent(QKeyEvent* event)
 #endif
             moveCursor(selectionEnd(), false);
         } else {
-            cursorForward(0, layoutDirection() == Qt::LeftToRight ? 1 : -1);
+            cursorForward(0, visual ? 1 : (layoutDirection() == Qt::LeftToRight ? 1 : -1));
         }
     }
     else if (event == QKeySequence::SelectNextChar) {
-        cursorForward(1, layoutDirection() == Qt::LeftToRight ? 1 : -1);
+        cursorForward(1, visual ? 1 : (layoutDirection() == Qt::LeftToRight ? 1 : -1));
     }
     else if (event == QKeySequence::MoveToPreviousChar) {
 #if !defined(Q_WS_WIN) || defined(QT_NO_COMPLETER)
@@ -1664,11 +1665,11 @@ void QLineControl::processKeyEvent(QKeyEvent* event)
 #endif
             moveCursor(selectionStart(), false);
         } else {
-            cursorForward(0, layoutDirection() == Qt::LeftToRight ? -1 : 1);
+            cursorForward(0, visual ? -1 : (layoutDirection() == Qt::LeftToRight ? -1 : 1));
         }
     }
     else if (event == QKeySequence::SelectPreviousChar) {
-        cursorForward(1, layoutDirection() == Qt::LeftToRight ? -1 : 1);
+        cursorForward(1, visual ? -1 : (layoutDirection() == Qt::LeftToRight ? -1 : 1));
     }
     else if (event == QKeySequence::MoveToNextWord) {
         if (echoMode() == QLineEdit::Normal)
diff --git a/src/gui/widgets/qlinecontrol_p.h b/src/gui/widgets/qlinecontrol_p.h
index 3c505c8696..0042f17261 100644
--- a/src/gui/widgets/qlinecontrol_p.h
+++ b/src/gui/widgets/qlinecontrol_p.h
@@ -160,6 +160,8 @@ public:
     int cursorWidth() const { return m_cursorWidth; }
     void setCursorWidth(int value) { m_cursorWidth = value; }
 
+    QTextCursor::MoveStyle cursorMoveStyle() const { return m_textLayout.cursorMoveStyle(); }
+    void setCursorMoveStyle(QTextCursor::MoveStyle style) { m_textLayout.setCursorMoveStyle(style); }
 
     void moveCursor(int pos, bool mark = false);
     void cursorForward(bool mark, int steps)
@@ -167,10 +169,12 @@ public:
         int c = m_cursor;
         if (steps > 0) {
             while (steps--)
-                c = m_textLayout.nextCursorPosition(c);
+                c = cursorMoveStyle() == QTextCursor::Visual ? m_textLayout.rightCursorPosition(c)
+                                                             : m_textLayout.nextCursorPosition(c);
         } else if (steps < 0) {
             while (steps++)
-                c = m_textLayout.previousCursorPosition(c);
+                c = cursorMoveStyle() == QTextCursor::Visual ? m_textLayout.leftCursorPosition(c)
+                                                             : m_textLayout.previousCursorPosition(c);
         }
         moveCursor(c, mark);
     }
diff --git a/src/gui/widgets/qlineedit.cpp b/src/gui/widgets/qlineedit.cpp
index 07bd2733f2..43c3f52d2b 100644
--- a/src/gui/widgets/qlineedit.cpp
+++ b/src/gui/widgets/qlineedit.cpp
@@ -1112,6 +1112,34 @@ void QLineEdit::setDragEnabled(bool b)
 
 
 /*!
+  \property QLineEdit::cursorMoveStyle
+  \brief the movement style of cursor in this line edit
+  \since 4.8
+
+  When this property is set to QTextCursor::Visual, the line edit will use visual
+  movement style. Pressing the left arrow key will always cause the cursor to move
+  left, regardless of the text's writing direction. The same behavior applies to
+  right arrow key.
+
+  When the property is QTextCursor::Logical (the default), within a LTR text block,
+  increase cursor position when pressing left arrow key, decrease cursor position
+  when pressing the right arrow key. If the text block is right to left, the opposite
+  behavior applies.
+*/
+
+QTextCursor::MoveStyle QLineEdit::cursorMoveStyle() const
+{
+    Q_D(const QLineEdit);
+    return d->control->cursorMoveStyle();
+}
+
+void QLineEdit::setCursorMoveStyle(QTextCursor::MoveStyle style)
+{
+    Q_D(QLineEdit);
+    d->control->setCursorMoveStyle(style);
+}
+
+/*!
     \property QLineEdit::acceptableInput
     \brief whether the input satisfies the inputMask and the
     validator.
diff --git a/src/gui/widgets/qlineedit.h b/src/gui/widgets/qlineedit.h
index 636cee7bb0..73a736c690 100644
--- a/src/gui/widgets/qlineedit.h
+++ b/src/gui/widgets/qlineedit.h
@@ -43,6 +43,7 @@
 #define QLINEEDIT_H
 
 #include <QtGui/qframe.h>
+#include <QtGui/qtextcursor.h>
 #include <QtCore/qstring.h>
 #include <QtCore/qmargins.h>
 
@@ -158,6 +159,9 @@ public:
     void setDragEnabled(bool b);
     bool dragEnabled() const;
 
+    void setCursorMoveStyle(QTextCursor::MoveStyle style);
+    QTextCursor::MoveStyle cursorMoveStyle() const;
+
     QString inputMask() const;
     void setInputMask(const QString &inputMask);
     bool hasAcceptableInput() const;