QPen Class

The QPen class defines how QPainter draws lines and outlines. More…

List of all members, including inherited members

Public Functions

Detailed Description

A pen has a color, a width and a style. The default pen is a black solid line one pixel wide.

QPainter painter(&image);
painter.setPen(QPen(Qt::red, 3));
painter.drawLine(0, 0, 100, 100);

painter.setRenderHint(QPainter::Antialiasing);
const Qt::PenCapStyle caps[3] = {Qt::FlatCap, Qt::SquareCap, Qt::RoundCap};
const Qt::PenStyle styles[3] = {Qt::SolidLine, Qt::DashLine, Qt::DashDotLine};
for (int i = 0; i < 3; ++i) {
    QPen pen(QColor(30, 30, 80), 14, styles[i], caps[i], Qt::RoundJoin);
    pen.setDashOffset(phase / 10);
    painter.setPen(pen);
    const qreal y = size.height() * (i + 1) / 5.0;
    painter.drawLine(QPointF(30, y), QPointF(size.width() / 2 - 20, y));
}
// Arcs of a gauge, with round caps.
const qreal side = std::min(size.height() - 60, size.width() / 2 - 60);
const QRectF dial(size.width() * 0.75 - side / 2, (size.height() - side) / 2, side, side);
painter.setPen(QPen(QColor(220, 220, 230), 18, Qt::SolidLine, Qt::RoundCap));
painter.drawArc(dial, -45 * 16, 270 * 16);
painter.setPen(QPen(QColor(40, 170, 110), 18, Qt::SolidLine, Qt::RoundCap));
painter.drawArc(dial, 225 * 16, -static_cast<int>(std::fmod(phase, 270.0) * 16));

Paths, transformed shapes and floating-point coordinates are drawn with the cap and join styles, dashes and miter limit of the pen; drawing with integer coordinates and no transformation other than a translation draws plain lines and outlines of whole pixels.

See also QBrush and QPainter.

Differences from Qt

Member Function Documentation

QPen::QPen()

Constructs a black solid pen one pixel wide.

QPen::QPen(Qt::PenStyle style)

This is an overloaded function.

Constructs a black pen with the given style.

QPen::QPen(const QColor &color)

This is an overloaded function.

Constructs a solid pen one pixel wide with the given color.

QPen::QPen(const QBrush &brush, qreal width, Qt::PenStyle style = Qt::SolidLine, Qt::PenCapStyle cap = Qt::SquareCap, Qt::PenJoinStyle join = Qt::BevelJoin)

This is an overloaded function.

Constructs a pen with the given brush, width and style.

QBrush QPen::brush() const

Returns the brush that gives the pen its color.

See also setBrush().

Qt::PenCapStyle QPen::capStyle() const

Returns how the ends of lines are drawn; Qt::SquareCap by default.

QColor QPen::color() const

Returns the pen color.

See also setColor().

qreal QPen::dashOffset() const

Returns where in the dash pattern lines start, in units of the pen width.

QList<qreal> QPen::dashPattern() const

Returns the dashes and gaps of the pen, in units of its width: the pattern of its style, or the one set with setDashPattern().

bool QPen::isCosmetic() const

Returns true if the width of the pen is in device pixels, not affected by transformations: if it was set cosmetic or has a width of 0. Otherwise returns false.

bool QPen::isSolid() const

Returns true if the style is Qt::SolidLine; otherwise returns false.

Qt::PenJoinStyle QPen::joinStyle() const

Returns how the segments of lines meet; Qt::BevelJoin by default.

qreal QPen::miterLimit() const

Returns how far a miter join may reach, in units of the pen width; 2 by default.

void QPen::setBrush(const QBrush &brush)

Sets the brush of the pen to brush.

See also brush().

void QPen::setCapStyle(Qt::PenCapStyle style)

Sets how the ends of lines are drawn to style.

void QPen::setColor(const QColor &color)

Sets the pen color to color.

See also color().

void QPen::setCosmetic(bool cosmetic)

Makes the width of the pen in device pixels if cosmetic is true.

void QPen::setDashOffset(qreal offset)

Sets where in the dash pattern lines start to offset.

void QPen::setDashPattern(const QList<qreal> &pattern)

Sets the dashes and gaps of the pen to pattern, alternating, in units of its width, and makes its style Qt::CustomDashLine. A pattern with an odd number of entries is ignored.

void QPen::setJoinStyle(Qt::PenJoinStyle style)

Sets how the segments of lines meet to style.

void QPen::setMiterLimit(qreal limit)

Sets how far a miter join may reach to limit pen widths.

void QPen::setStyle(Qt::PenStyle style)

Sets the pen style to style.

See also style().

void QPen::setWidth(int width)

Sets the pen width to width pixels.

See also width().

void QPen::setWidthF(qreal width)

Sets the pen width to width.

See also widthF().

Qt::PenStyle QPen::style() const

Returns the pen style.

See also setStyle().

int QPen::width() const

Returns the pen width rounded to whole pixels.

See also setWidth() and widthF().

qreal QPen::widthF() const

Returns the pen width.

See also setWidthF().