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

1 files changed, 60 insertions, 0 deletions

diff --git a/src/gui/text/qtextengine_p.h b/src/gui/text/qtextengine_p.h
index 366c5c3207..c476485c1d 100644
--- a/src/gui/text/qtextengine_p.h
+++ b/src/gui/text/qtextengine_p.h
@@ -64,6 +64,7 @@
 #include "QtGui/qpaintengine.h"
 #include "QtGui/qtextobject.h"
 #include "QtGui/qtextoption.h"
+#include "QtGui/qtextcursor.h"
 #include "QtCore/qset.h"
 #include "QtCore/qdebug.h"
 #ifndef QT_BUILD_COMPAT_LIB
@@ -471,6 +472,7 @@ public:
     void shape(int item) const;
 
     void justify(const QScriptLine &si);
+    QFixed alignLine(const QScriptLine &line);
 
     QFixed width(int charFrom, int numChars) const;
     glyph_metrics_t boundingBox(int from,  int len) const;
@@ -586,12 +588,18 @@ public:
     uint cacheGlyphs : 1;
     uint stackEngine : 1;
     uint forceJustification : 1;
+    uint visualMovement : 1;
 
     int *underlinePositions;
 
     mutable LayoutData *layoutData;
 
     inline bool hasFormats() const { return (block.docHandle() || specialData); }
+    inline bool visualCursorMovement() const
+    {
+        return (visualMovement ||
+                (block.docHandle() ? block.docHandle()->defaultCursorMoveStyle == QTextCursor::Visual : false));
+    }
 
     struct SpecialData {
         int preeditPosition;
@@ -611,6 +619,13 @@ public:
     void shapeLine(const QScriptLine &line);
     QFixed leadingSpaceWidth(const QScriptLine &line);
 
+    QFixed offsetInLigature(const QScriptItem *si, int pos, int max, int glyph_pos);
+    int previousLogicalPosition(int oldPos) const;
+    int nextLogicalPosition(int oldPos) const;
+    int lineNumberForTextPosition(int pos);
+    int positionAfterVisualMovement(int oldPos, QTextCursor::MoveOperation op);
+    void insertionPointsForLine(int lineNum, QVector<int> &insertionPoints);
+
 private:
     void setBoundary(int strPos) const;
     void addRequiredBoundaries() const;
@@ -625,6 +640,8 @@ private:
     void splitItem(int item, int pos) const;
 
     void resolveAdditionalFormats() const;
+    int endOfLine(int lineNum);
+    int beginningOfLine(int lineNum);
 };
 
 class QStackTextEngine : public QTextEngine {
@@ -635,6 +652,49 @@ public:
     void *_memory[MemSize];
 };
 
+struct QTextLineItemIterator
+{
+    QTextLineItemIterator(QTextEngine *eng, int lineNum, const QPointF &pos = QPointF(),
+                          const QTextLayout::FormatRange *_selection = 0);
+
+    inline bool atEnd() const { return logicalItem >= nItems - 1; }
+    inline bool atBeginning() const { return logicalItem <= 0; }
+    QScriptItem &next();
+
+    bool getSelectionBounds(QFixed *selectionX, QFixed *selectionWidth) const;
+    inline bool isOutsideSelection() const {
+        QFixed tmp1, tmp2;
+        return !getSelectionBounds(&tmp1, &tmp2);
+    }
+
+    QTextEngine *eng;
+
+    QFixed x;
+    QFixed pos_x;
+    const QScriptLine &line;
+    QScriptItem *si;
+
+    int lineNum;
+    int lineEnd;
+    int firstItem;
+    int lastItem;
+    int nItems;
+    int logicalItem;
+    int item;
+    int itemLength;
+
+    int glyphsStart;
+    int glyphsEnd;
+    int itemStart;
+    int itemEnd;
+
+    QFixed itemWidth;
+
+    QVarLengthArray<int> visualOrder;
+    QVarLengthArray<uchar> levels;
+
+    const QTextLayout::FormatRange *selection;
+};
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QTextEngine::ShaperFlags)