Customize the QLineEdit, Cursor can't move one char by LeftButton / RightButton.

[zimang]

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.

#include <QtGui>
#include <QtCore>
 
class Edit : public QLineEdit{
 
    public:
 
        Edit(const QString &t, QWidget *pParent = 0) : QLineEdit(t, pParent){
            font = QFont("Sans");
            font.setPixelSize(26);
            setFixedSize(640, 220);
            setTextMargins(4, 0, 4, 0);
        }
 
    protected:
        void paintEvent(QPaintEvent *pEvent){
            QPainter painter(this);
            QRect r = rect();
            //frame
            int x2 = r.width() - 1, y2 = r.height() - 1;
            painter.fillRect(r, QBrush(QColor(79, 79, 104, 255)));
            painter.setPen(QPen(QColor(64, 64, 64, 255), 1));
            painter.drawLine(0, 0, x2, 0);
 
            painter.drawLine(0, 0, 0, y2);
            painter.setPen(QPen(QColor(92, 92, 92, 255), 1));
            painter.drawLine(x2, y2, 1, y2);
            painter.drawLine(x2, y2, x2, 1);
            painter.setPen(QPen(QColor(19, 19, 19, 255), 1));
            painter.drawRect(QRect(1, 1, r.width() - 3, r.height() - 3));
 
            //set clipping
            int lm, tm, rm, bm;
            getTextMargins(&lm, &tm, &rm, &bm);
            r.setX(r.x() + lm);
            r.setY(r.y() + tm);
            r.setRight(r.right() - rm);
            r.setBottom(r.bottom() - bm);
            painter.setClipRect(r);
 
            painter.setPen(QPen(QColor(196, 196, 196, 255), 1));
            QFontMetrics fm(font);
            QTextLayout tl(text(), font, this);
            tl.beginLayout();
            QTextLine line = tl.createLine();
            if( !line.isValid() ){ return; }
 
            tl.endLayout();
            QRect lineRect(r.x(), r.y() + (r.height() - qRound(line.height()) + 1) / 2,
                    r.width() - 1, qRound(line.height()));
            //painter.drawRect(lineRect);
            int ccc = cursorPosition();
            int cix = qRound(line.cursorToX(&ccc));
            int minLB = qMax(0, -fm.minLeftBearing());
            int minRB = qMax(0, -fm.minRightBearing());
            int widthUsed = qRound(line.naturalTextWidth()) + 1 + minRB;
            int hscroll;
 
            if( (minLB + widthUsed) <= lineRect.width() ){
                //hscroll = 0;
                Qt::Alignment va = QStyle::visualAlignment(layoutDirection(), QFlag(this->alignment()));
                va &= ~(Qt::AlignAbsolute|Qt::AlignVertical_Mask);
                switch (va) {
                    case Qt::AlignRight:
                        hscroll = widthUsed - lineRect.width() + 1;
                        break;
                    case Qt::AlignHCenter:
                        hscroll = (widthUsed - lineRect.width()) / 2;
                        break;
                    default:
                        // Left
                        hscroll = 0;
                        break;
                }
                hscroll -= minLB;
            }else if( cix - hscroll >= lineRect.width() ){
                hscroll = cix - lineRect.width() + 1;
            }else if( cix - hscroll < 0 && hscroll < widthUsed ){
                hscroll = cix;
            }else if( widthUsed - hscroll < lineRect.width() ){
                hscroll = widthUsed - lineRect.width() + 1;
            }
            QPoint topLeft = lineRect.topLeft() - QPoint(hscroll, line.ascent() - fm.ascent());
 
            QVector<QTextLayout::FormatRange> selections;
 
            QTextLayout::FormatRange o;
            if( hasSelectedText() ){
 
                o.start = selectionStart();
                o.length = selectedText().length();
                o.format.setBackground(QColor(88, 101, 134, 255));
                o.format.setForeground(QColor(196, 196, 196, 255));
                selections.append(o);
            }
 
            tl.draw(&painter, topLeft, selections);
            painter.setPen(QPen(QColor(200, 0, 0, 255), 2));
            //painter.drawLine(cix, lineRect.y(), cix, lineRect.y() + lineRect.height());
            tl.drawCursor(&painter, topLeft, cix, 2);
 
        }
 
    private:
        QFont font;
};
 
int main(int argc, char *argv[]){
    QApplication a(argc, argv);
 
    QWidget *w = new QWidget;
 
    w->setPalette(QPalette(QColor(77, 77, 77, 255)));
    QHBoxLayout *l = new QHBoxLayout(w);
    Edit *e1 = new Edit(QString("test1"));
    e1->setAlignment(Qt::AlignCenter);
 
    QLineEdit *e2 = new QLineEdit(QString("test2"));
 
    e2->setFixedSize(640, 220);
 
    e2->setAlignment(Qt::AlignCenter);
 
    l->addWidget(e1);
    l->addWidget(e2);
    w->show();
 
    return a.exec();
}

#include <QtGui>
#include <QtCore>

class Edit : public QLineEdit{

    public:

        Edit(const QString &t, QWidget *pParent = 0) : QLineEdit(t, pParent){
            font = QFont("Sans");
            font.setPixelSize(26);
            setFixedSize(640, 220);
            setTextMargins(4, 0, 4, 0);
        }

    protected:
        void paintEvent(QPaintEvent *pEvent){
            QPainter painter(this);
            QRect r = rect();
            //frame
            int x2 = r.width() - 1, y2 = r.height() - 1;
            painter.fillRect(r, QBrush(QColor(79, 79, 104, 255)));
            painter.setPen(QPen(QColor(64, 64, 64, 255), 1));
            painter.drawLine(0, 0, x2, 0);

            painter.drawLine(0, 0, 0, y2);
            painter.setPen(QPen(QColor(92, 92, 92, 255), 1));
            painter.drawLine(x2, y2, 1, y2);
            painter.drawLine(x2, y2, x2, 1);
            painter.setPen(QPen(QColor(19, 19, 19, 255), 1));
            painter.drawRect(QRect(1, 1, r.width() - 3, r.height() - 3));

            //set clipping
            int lm, tm, rm, bm;
            getTextMargins(&lm, &tm, &rm, &bm);
            r.setX(r.x() + lm);
            r.setY(r.y() + tm);
            r.setRight(r.right() - rm);
            r.setBottom(r.bottom() - bm);
            painter.setClipRect(r);

            painter.setPen(QPen(QColor(196, 196, 196, 255), 1));
            QFontMetrics fm(font);
            QTextLayout tl(text(), font, this);
            tl.beginLayout();
            QTextLine line = tl.createLine();
            if( !line.isValid() ){ return; }

            tl.endLayout();
            QRect lineRect(r.x(), r.y() + (r.height() - qRound(line.height()) + 1) / 2,
                    r.width() - 1, qRound(line.height()));
            //painter.drawRect(lineRect);
            int ccc = cursorPosition();
            int cix = qRound(line.cursorToX(&ccc));
            int minLB = qMax(0, -fm.minLeftBearing());
            int minRB = qMax(0, -fm.minRightBearing());
            int widthUsed = qRound(line.naturalTextWidth()) + 1 + minRB;
            int hscroll;

            if( (minLB + widthUsed) <= lineRect.width() ){
                //hscroll = 0;
                Qt::Alignment va = QStyle::visualAlignment(layoutDirection(), QFlag(this->alignment()));
                va &= ~(Qt::AlignAbsolute|Qt::AlignVertical_Mask);
                switch (va) {
                    case Qt::AlignRight:
                        hscroll = widthUsed - lineRect.width() + 1;
                        break;
                    case Qt::AlignHCenter:
                        hscroll = (widthUsed - lineRect.width()) / 2;
                        break;
                    default:
                        // Left
                        hscroll = 0;
                        break;
                }
                hscroll -= minLB;
            }else if( cix - hscroll >= lineRect.width() ){
                hscroll = cix - lineRect.width() + 1;
            }else if( cix - hscroll < 0 && hscroll < widthUsed ){
                hscroll = cix;
            }else if( widthUsed - hscroll < lineRect.width() ){
                hscroll = widthUsed - lineRect.width() + 1;
            }
            QPoint topLeft = lineRect.topLeft() - QPoint(hscroll, line.ascent() - fm.ascent());

            QVector<QTextLayout::FormatRange> selections;

            QTextLayout::FormatRange o;
            if( hasSelectedText() ){

                o.start = selectionStart();
                o.length = selectedText().length();
                o.format.setBackground(QColor(88, 101, 134, 255));
                o.format.setForeground(QColor(196, 196, 196, 255));
                selections.append(o);
            }

            tl.draw(&painter, topLeft, selections);
            painter.setPen(QPen(QColor(200, 0, 0, 255), 2));
            //painter.drawLine(cix, lineRect.y(), cix, lineRect.y() + lineRect.height());
            tl.drawCursor(&painter, topLeft, cix, 2);

        }

    private:
        QFont font;
};

int main(int argc, char *argv[]){
    QApplication a(argc, argv);

    QWidget *w = new QWidget;

    w->setPalette(QPalette(QColor(77, 77, 77, 255)));
    QHBoxLayout *l = new QHBoxLayout(w);
    Edit *e1 = new Edit(QString("test1"));
    e1->setAlignment(Qt::AlignCenter);

    QLineEdit *e2 = new QLineEdit(QString("test2"));

    e2->setFixedSize(640, 220);

    e2->setAlignment(Qt::AlignCenter);

    l->addWidget(e1);
    l->addWidget(e2);
    w->show();

    return a.exec();
}

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[high_flyer]

Can you explain in words the logic in the calculation of 'topLeft' in your code?