QEasingCurve

The QEasingCurve class provides easing curves for controlling animation. More

Inheritance diagram of PySide2.QtCore.QEasingCurve

New in version 4.6.

Synopsis

Functions

Detailed Description

Easing curves describe a function that controls how the speed of the interpolation between 0 and 1 should be. Easing curves allow transitions from one value to another to appear more natural than a simple constant speed would allow. The QEasingCurve class is usually used in conjunction with the QVariantAnimation and QPropertyAnimation classes but can be used on its own. It is usually used to accelerate the interpolation from zero velocity (ease in) or decelerate to zero velocity (ease out). Ease in and ease out can also be combined in the same easing curve.

To calculate the speed of the interpolation, the easing curve provides the function valueForProgress() , where the progress argument specifies the progress of the interpolation: 0 is the start value of the interpolation, 1 is the end value of the interpolation. The returned value is the effective progress of the interpolation. If the returned value is the same as the input value for all input values the easing curve is a linear curve. This is the default behaviour.

For example,

QEasingCurve easing(QEasingCurve::InOutQuad);

for (qreal t = 0.0; t < 1.0; t += 0.1)
    qWarning() << "Effective progress" << t << "is"
               << easing.valueForProgress(t);

will print the effective progress of the interpolation between 0 and 1.

When using a QPropertyAnimation , the associated easing curve will be used to control the progress of the interpolation between startValue and endValue:

QPropertyAnimation animation;
animation.setStartValue(0);
animation.setEndValue(1000);
animation.setDuration(1000);
animation.setEasingCurve(QEasingCurve::InOutQuad);

The ability to set an amplitude, overshoot, or period depends on the QEasingCurve type. Amplitude access is available to curves that behave as springs such as elastic and bounce curves. Changing the amplitude changes the height of the curve. Period access is only available to elastic curves and setting a higher period slows the rate of bounce. Only curves that have “boomerang” behaviors such as the InBack , OutBack , InOutBack , and OutInBack have overshoot settings. These curves will interpolate beyond the end points and return to the end point, acting similar to a boomerang.

The Easing Curves Example contains samples of QEasingCurve types and lets you change the curve settings.

class PySide2.QtCore.QEasingCurve([type=Linear])

PySide2.QtCore.QEasingCurve(other)

param type

Type

param other

PySide2.QtCore.QEasingCurve

Constructs an easing curve of the given type .

PySide2.QtCore.QEasingCurve.Type

The type of easing curve.

Constant

Description

QEasingCurve.Linear

../../_images/qeasingcurve-linear.png

Constant

Description

QEasingCurve.InQuad

../../_images/qeasingcurve-inquad.png

Constant

Description

QEasingCurve.OutQuad

../../_images/qeasingcurve-outquad.png

Constant

Description

QEasingCurve.InOutQuad

../../_images/qeasingcurve-inoutquad.png

Constant

Description

QEasingCurve.OutInQuad

../../_images/qeasingcurve-outinquad.png

Constant

Description

QEasingCurve.InCubic

../../_images/qeasingcurve-incubic.png

Constant

Description

QEasingCurve.OutCubic

../../_images/qeasingcurve-outcubic.png

Constant

Description

QEasingCurve.InOutCubic

../../_images/qeasingcurve-inoutcubic.png

Constant

Description

QEasingCurve.OutInCubic

../../_images/qeasingcurve-outincubic.png

Constant

Description

QEasingCurve.InQuart

../../_images/qeasingcurve-inquart.png

Constant

Description

QEasingCurve.OutQuart

../../_images/qeasingcurve-outquart.png

Constant

Description

QEasingCurve.InOutQuart

../../_images/qeasingcurve-inoutquart.png

Constant

Description

QEasingCurve.OutInQuart

../../_images/qeasingcurve-outinquart.png

Constant

Description

QEasingCurve.InQuint

../../_images/qeasingcurve-inquint.png

Constant

Description

QEasingCurve.OutQuint

../../_images/qeasingcurve-outquint.png

Constant

Description

QEasingCurve.InOutQuint

../../_images/qeasingcurve-inoutquint.png

Constant

Description

QEasingCurve.OutInQuint

../../_images/qeasingcurve-outinquint.png

Constant

Description

QEasingCurve.InSine

../../_images/qeasingcurve-insine.png

Constant

Description

QEasingCurve.OutSine

../../_images/qeasingcurve-outsine.png

Constant

Description

QEasingCurve.InOutSine

../../_images/qeasingcurve-inoutsine.png

Constant

Description

QEasingCurve.OutInSine

../../_images/qeasingcurve-outinsine.png

Constant

Description

QEasingCurve.InExpo

../../_images/qeasingcurve-inexpo.png

Constant

Description

QEasingCurve.OutExpo

../../_images/qeasingcurve-outexpo.png

Constant

Description

QEasingCurve.InOutExpo

../../_images/qeasingcurve-inoutexpo.png

Constant

Description

QEasingCurve.OutInExpo

../../_images/qeasingcurve-outinexpo.png

Constant

Description

QEasingCurve.InCirc

../../_images/qeasingcurve-incirc.png

Constant

Description

QEasingCurve.OutCirc

../../_images/qeasingcurve-outcirc.png

Constant

Description

QEasingCurve.InOutCirc

../../_images/qeasingcurve-inoutcirc.png

Constant

Description

QEasingCurve.OutInCirc

../../_images/qeasingcurve-outincirc.png

Constant

Description

QEasingCurve.InElastic

../../_images/qeasingcurve-inelastic.png
amplitude**period

Constant

Description

QEasingCurve.OutElastic

../../_images/qeasingcurve-outelastic.png
amplitude**period

Constant

Description

QEasingCurve.InOutElastic

../../_images/qeasingcurve-inoutelastic.png

Constant

Description

QEasingCurve.OutInElastic

../../_images/qeasingcurve-outinelastic.png

Constant

Description

QEasingCurve.InBack

../../_images/qeasingcurve-inback.png

Constant

Description

QEasingCurve.OutBack

../../_images/qeasingcurve-outback.png

Constant

Description

QEasingCurve.InOutBack

../../_images/qeasingcurve-inoutback.png

Constant

Description

QEasingCurve.OutInBack

../../_images/qeasingcurve-outinback.png

Constant

Description

QEasingCurve.InBounce

../../_images/qeasingcurve-inbounce.png

Constant

Description

QEasingCurve.OutBounce

../../_images/qeasingcurve-outbounce.png

Constant

Description

QEasingCurve.InOutBounce

../../_images/qeasingcurve-inoutbounce.png

Constant

Description

QEasingCurve.OutInBounce

../../_images/qeasingcurve-outinbounce.png

Constant

Description

QEasingCurve.BezierSpline

Allows defining a custom easing curve using a cubic bezier spline

QEasingCurve.TCBSpline

Allows defining a custom easing curve using a TCB spline

QEasingCurve.Custom

This is returned if the user specified a custom curve type with setCustomType() . Note that you cannot call setType() with this value, but type() can return it.

PySide2.QtCore.QEasingCurve.addCubicBezierSegment(c1, c2, endPoint)
Parameters

Adds a segment of a cubic bezier spline to define a custom easing curve. It is only applicable if type() is BezierSpline . Note that the spline implicitly starts at (0.0, 0.0) and has to end at (1.0, 1.0) to be a valid easing curve. c1 and c2 are the control points used for drawing the curve. endPoint is the endpoint of the curve.

PySide2.QtCore.QEasingCurve.addTCBSegment(nextPoint, t, c, b)
Parameters

Adds a segment of a TCB bezier spline to define a custom easing curve. It is only applicable if type() is TCBSpline . The spline has to start explitly at (0.0, 0.0) and has to end at (1.0, 1.0) to be a valid easing curve. The tension t changes the length of the tangent vector. The continuity c changes the sharpness in change between the tangents. The bias b changes the direction of the tangent vector. nextPoint is the sample position. All three parameters are valid between -1 and 1 and define the tangent of the control point. If all three parameters are 0 the resulting spline is a Catmull-Rom spline. The begin and endpoint always have a bias of -1 and 1, since the outer tangent is not defined.

PySide2.QtCore.QEasingCurve.amplitude()
Return type

float

Returns the amplitude. This is not applicable for all curve types. It is only applicable for bounce and elastic curves (curves of type() InBounce , OutBounce , InOutBounce , OutInBounce , InElastic , OutElastic , InOutElastic or OutInElastic ).

See also

setAmplitude()

PySide2.QtCore.QEasingCurve.customType()
Return type

object

PySide2.QtCore.QEasingCurve.__ne__(other)
Parameters

otherPySide2.QtCore.QEasingCurve

Return type

bool

Compare this easing curve with other and returns true if they are not equal. It will also compare the properties of a curve.

See also

operator==()

PySide2.QtCore.QEasingCurve.__eq__(other)
Parameters

otherPySide2.QtCore.QEasingCurve

Return type

bool

Compare this easing curve with other and returns true if they are equal. It will also compare the properties of a curve.

PySide2.QtCore.QEasingCurve.overshoot()
Return type

float

Returns the overshoot. This is not applicable for all curve types. It is only applicable if type() is InBack , OutBack , InOutBack or OutInBack .

See also

setOvershoot()

PySide2.QtCore.QEasingCurve.period()
Return type

float

Returns the period. This is not applicable for all curve types. It is only applicable if type() is InElastic , OutElastic , InOutElastic or OutInElastic .

See also

setPeriod()

PySide2.QtCore.QEasingCurve.setAmplitude(amplitude)
Parameters

amplitude – float

Sets the amplitude to amplitude .

This will set the amplitude of the bounce or the amplitude of the elastic “spring” effect. The higher the number, the higher the amplitude.

See also

amplitude()

PySide2.QtCore.QEasingCurve.setCustomType(arg__1)
Parameters

arg__1 – object

PySide2.QtCore.QEasingCurve.setOvershoot(overshoot)
Parameters

overshoot – float

Sets the overshoot to overshoot .

0 produces no overshoot, and the default value of 1.70158 produces an overshoot of 10 percent.

See also

overshoot()

PySide2.QtCore.QEasingCurve.setPeriod(period)
Parameters

period – float

Sets the period to period . Setting a small period value will give a high frequency of the curve. A large period will give it a small frequency.

See also

period()

PySide2.QtCore.QEasingCurve.setType(type)
Parameters

typeType

Sets the type of the easing curve to type .

See also

type()

PySide2.QtCore.QEasingCurve.swap(other)
Parameters

otherPySide2.QtCore.QEasingCurve

Swaps curve other with this curve. This operation is very fast and never fails.

PySide2.QtCore.QEasingCurve.toCubicSpline()
Return type

Returns the cubicBezierSpline that defines a custom easing curve. If the easing curve does not have a custom bezier easing curve the list is empty.

PySide2.QtCore.QEasingCurve.type()
Return type

Type

Returns the type of the easing curve.

See also

setType()

PySide2.QtCore.QEasingCurve.valueForProgress(progress)
Parameters

progress – float

Return type

float

Return the effective progress for the easing curve at progress . Whereas progress must be between 0 and 1, the returned effective progress can be outside those bounds. For example, InBack will return negative values in the beginning of the function.