I draw the QLineEdit by paintEnvent(), but the cursor can't move one by one throught the left or right button. I press the right button, it moves to the end, and the beginning when I pressing the left button. But the cursor's real point is right, beacause I can backspace the character by pressing Backspace.

It seems the show problem.

Thanks a lot.
Qt Code: 
  1. #include <QtGui>
  2. #include <QtCore>
  3.  
  4. class Edit : public QLineEdit{
  5.  
  6.     public:
  7.  
  8.         Edit(const QString &t, QWidget *pParent = 0) : QLineEdit(t, pParent){
  9.             font = QFont("Sans");
  10.             font.setPixelSize(26);
  11.             setFixedSize(640, 220);
  12.             setTextMargins(4, 0, 4, 0);
  13.         }
  14.  
  15.     protected:
  16.         void paintEvent(QPaintEvent *pEvent){
  17.             QPainter painter(this);
  18.             QRect r = rect();
  19.             //frame
  20.             int x2 = r.width() - 1, y2 = r.height() - 1;
  21.             painter.fillRect(r, QBrush(QColor(79, 79, 104, 255)));
  22.             painter.setPen(QPen(QColor(64, 64, 64, 255), 1));
  23.             painter.drawLine(0, 0, x2, 0);
  24.  
  25.             painter.drawLine(0, 0, 0, y2);
  26.             painter.setPen(QPen(QColor(92, 92, 92, 255), 1));
  27.             painter.drawLine(x2, y2, 1, y2);
  28.             painter.drawLine(x2, y2, x2, 1);
  29.             painter.setPen(QPen(QColor(19, 19, 19, 255), 1));
  30.             painter.drawRect(QRect(1, 1, r.width() - 3, r.height() - 3));
  31.  
  32.             //set clipping
  33.             int lm, tm, rm, bm;
  34.             getTextMargins(&lm, &tm, &rm, &bm);
  35.             r.setX(r.x() + lm);
  36.             r.setY(r.y() + tm);
  37.             r.setRight(r.right() - rm);
  38.             r.setBottom(r.bottom() - bm);
  39.             painter.setClipRect(r);
  40.  
  41.             painter.setPen(QPen(QColor(196, 196, 196, 255), 1));
  42.             QFontMetrics fm(font);
  43.             QTextLayout tl(text(), font, this);
  44.             tl.beginLayout();
  45.             QTextLine line = tl.createLine();
  46.             if( !line.isValid() ){ return; }
  47.  
  48.             tl.endLayout();
  49.             QRect lineRect(r.x(), r.y() + (r.height() - qRound(line.height()) + 1) / 2,
  50.                     r.width() - 1, qRound(line.height()));
  51.             //painter.drawRect(lineRect);
  52.             int ccc = cursorPosition();
  53.             int cix = qRound(line.cursorToX(&ccc));
  54.             int minLB = qMax(0, -fm.minLeftBearing());
  55.             int minRB = qMax(0, -fm.minRightBearing());
  56.             int widthUsed = qRound(line.naturalTextWidth()) + 1 + minRB;
  57.             int hscroll;
  58.  
  59.             if( (minLB + widthUsed) <= lineRect.width() ){
  60.                 //hscroll = 0;
  61.                 Qt::Alignment va = QStyle::visualAlignment(layoutDirection(), QFlag(this->alignment()));
  62.                 va &= ~(Qt::AlignAbsolute|Qt::AlignVertical_Mask);
  63.                 switch (va) {
  64.                     case Qt::AlignRight:
  65.                         hscroll = widthUsed - lineRect.width() + 1;
  66.                         break;
  67.                     case Qt::AlignHCenter:
  68.                         hscroll = (widthUsed - lineRect.width()) / 2;
  69.                         break;
  70.                     default:
  71.                         // Left
  72.                         hscroll = 0;
  73.                         break;
  74.                 }
  75.                 hscroll -= minLB;
  76.             }else if( cix - hscroll >= lineRect.width() ){
  77.                 hscroll = cix - lineRect.width() + 1;
  78.             }else if( cix - hscroll < 0 && hscroll < widthUsed ){
  79.                 hscroll = cix;
  80.             }else if( widthUsed - hscroll < lineRect.width() ){
  81.                 hscroll = widthUsed - lineRect.width() + 1;
  82.             }
  83.             QPoint topLeft = lineRect.topLeft() - QPoint(hscroll, line.ascent() - fm.ascent());
  84.  
  85.             QVector<QTextLayout::FormatRange> selections;
  86.  
  87.             QTextLayout::FormatRange o;
  88.             if( hasSelectedText() ){
  89.  
  90.                 o.start = selectionStart();
  91.                 o.length = selectedText().length();
  92.                 o.format.setBackground(QColor(88, 101, 134, 255));
  93.                 o.format.setForeground(QColor(196, 196, 196, 255));
  94.                 selections.append(o);
  95.             }
  96.  
  97.             tl.draw(&painter, topLeft, selections);
  98.             painter.setPen(QPen(QColor(200, 0, 0, 255), 2));
  99.             //painter.drawLine(cix, lineRect.y(), cix, lineRect.y() + lineRect.height());
  100.             tl.drawCursor(&painter, topLeft, cix, 2);
  101.  
  102.         }
  103.  
  104.     private:
  105.         QFont font;
  106. };
  107.  
  108. int main(int argc, char *argv[]){
  109.     QApplication a(argc, argv);
  110.  
  111.     QWidget *w = new QWidget;
  112.  
  113.     w->setPalette(QPalette(QColor(77, 77, 77, 255)));
  114.     QHBoxLayout *l = new QHBoxLayout(w);
  115.     Edit *e1 = new Edit(QString("test1"));
  116.     e1->setAlignment(Qt::AlignCenter);
  117.  
  118.     QLineEdit *e2 = new QLineEdit(QString("test2"));
  119.  
  120.     e2->setFixedSize(640, 220);
  121.  
  122.     e2->setAlignment(Qt::AlignCenter);
  123.  
  124.     l->addWidget(e1);
  125.     l->addWidget(e2);
  126.     w->show();
  127.  
  128.     return a.exec();
  129. }
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