com.trolltech.qt.gui
Class QGradient

java.lang.Object
  com.trolltech.qt.internal.QSignalEmitterInternal
      com.trolltech.qt.QSignalEmitter
          com.trolltech.qt.QtJambiObject
              com.trolltech.qt.gui.QGradient

All Implemented Interfaces:

QtJambiInterface, java.lang.Cloneable

Direct Known Subclasses:

QConicalGradient, QLinearGradient, QRadialGradient

public abstract class QGradient
extends QtJambiObject
implements java.lang.Cloneable

The QGradient class is used in combination with QBrush to specify gradient fills. Qt currently supports three types of gradient fills:

• Linear gradients interpolate colors between start and end points.
• Radial gradients interpolate colors between a focal point and end points on a circle surrounding it.
• Conical gradients interpolate colors around a center point.

A gradient's type can be retrieved using the type() function. Each of the types is represented by a subclass of QGradient:

QLinearGradient	QRadialGradient	QConicalGradient

The colors in a gradient is defined using stop points of the QGradientStop type, i.e. a position and a color. Use the setColorAt() function to define a single stop point. Alternatively, use the setStops() function to define several stop points in one go. Note that the latter function replaces the current set of stop points.

It is the gradient's complete set of stop points (accessible through the stops() function) that describes how the gradient area should be filled. If no stop points have been specified, a gradient of black at 0 to white at 1 is used.

A diagonal linear gradient from black at (100, 100) to white at (200, 200) could be specified like this:

        QLinearGradient linearGrad = new QLinearGradient(new QPointF(100, 100),
                                                         new QPointF(200, 200));
        linearGrad.setColorAt(0, new QColor(Qt.GlobalColor.black));
        linearGrad.setColorAt(1, new QColor(Qt.GlobalColor.white));
    

A gradient can have an arbitrary number of stop points. The following would create a radial gradient starting with red in the center, blue and then green on the edges:

        QRadialGradient radialGrad =
            new QRadialGradient(new QPointF(100, 100), 100);
        radialGrad.setColorAt(0, new QColor(Qt.GlobalColor.red));
        radialGrad.setColorAt(0.5, new QColor(Qt.GlobalColor.blue));
        radialGrad.setColorAt(1, new QColor(Qt.GlobalColor.green));
    

It is possible to repeat or reflect the gradient outside its area by specifiying the spread method using the setSpread() function. The default is to pad the outside area with the color at the closest stop point. The currently set spread method can be retrieved using the spread() function. The QGradient::Spread enum defines three different methods:

PadSpread	RepeatSpread	ReflectSpread

Note that the setSpread() function only has effect for linear and radial gradients. The reason is that the conical gradient is closed by definition, i.e. the conical gradient fills the entire circle from 0 - 360 degrees, while the boundary of a radial or a linear gradient can be specified through its radius or final stop points, respectively.

The gradient coordinates can be specified in logical coordinates, relative to device coordinates, or relative to object bounding box coordinates. The coordinate mode can be set using the setCoordinateMode() function. The default is LogicalMode , where the gradient coordinates are specified in the same way as the object coordinates. To retrieve the currently set coordinate mode use coordinateMode().

See also:

The Gradients Demo, and QBrush.

Nested Class Summary

static class	QGradient.CoordinateMode This enum specifies how gradient coordinates map to the paint device on which the gradient is used.
static class	QGradient.Spread Specifies how the area outside the gradient area should be filled.
static class	QGradient.Type Specifies the type of gradient.

Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter

QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9

Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal

com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal

Field Summary

Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal

currentSender

Method Summary

QGradient	clone() This method is reimplemented for internal reasons
QGradient.CoordinateMode	coordinateMode() Returns the coordinate mode of this gradient.
void	setColorAt(double pos, QColor color) Creates a stop point at the given position with the given color.
void	setCoordinateMode(QGradient.CoordinateMode mode) Sets the coordinate mode of this gradient to mode.
void	setSpread(QGradient.Spread spread) Specifies the spread method that should be used for this gradient.
void	setStops(java.util.List stops) Replaces the current set of stop points with the given stops.
QGradient.Spread	spread() Returns the spread method use by this gradient.
java.util.List	stops() Returns the stop points for this gradient.
QGradient.Type	type() Returns the type of gradient.

Methods inherited from class com.trolltech.qt.QtJambiObject

dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr

Methods inherited from class com.trolltech.qt.QSignalEmitter

blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread

Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal

__qt_signalInitialization

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.trolltech.qt.QtJambiInterface

disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership

Method Detail

coordinateMode

public final QGradient.CoordinateMode coordinateMode()

Returns the coordinate mode of this gradient. The default mode is LogicalMode .

See also:

setCoordinateMode().

setColorAt

public final void setColorAt(double pos,
                             QColor color)

Creates a stop point at the given position with the given color. The given position must be in the range 0 to 1.

See also:

setStops(), and stops().

setCoordinateMode

public final void setCoordinateMode(QGradient.CoordinateMode mode)

Sets the coordinate mode of this gradient to mode. The default mode is LogicalMode .

See also:

coordinateMode().

setSpread

public final void setSpread(QGradient.Spread spread)

Specifies the spread method that should be used for this gradient.

Note that this function only has effect for linear and radial gradients.

See also:

spread().

setStops

public final void setStops(java.util.List stops)

Replaces the current set of stop points with the given stops. The positions of the points must be in the range 0 to 1, and must be sorted with the lowest point first.

spread

public final QGradient.Spread spread()

Returns the spread method use by this gradient. The default is PadSpread .

See also:

setSpread().

stops

public final java.util.List stops()

Returns the stop points for this gradient.

If no stop points have been specified, a gradient of black at 0 to white at 1 is used.

See also:

setStops(), and setColorAt().

type

public final QGradient.Type type()

Returns the type of gradient.

clone

public QGradient clone()

This method is reimplemented for internal reasons

Overrides:

clone in class java.lang.Object