QTimeLine

The QTimeLine class provides a timeline for controlling animations. More…

Inheritance diagram of PySide6.QtCore.QTimeLine

Synopsis

Functions

Virtual functions

Slots

Detailed Description

It’s most commonly used to animate a GUI control by calling a slot periodically. You can construct a timeline by passing its duration in milliseconds to QTimeLine ‘s constructor. The timeline’s duration describes for how long the animation will run. Then you set a suitable frame range by calling setFrameRange() . Finally connect the frameChanged() signal to a suitable slot in the widget you wish to animate (for example, setValue() in QProgressBar ). When you proceed to calling start() , QTimeLine will enter Running state, and start emitting frameChanged() at regular intervals, causing your widget’s connected property’s value to grow from the lower end to the upper and of your frame range, at a steady rate. You can specify the update interval by calling setUpdateInterval() . When done, QTimeLine enters NotRunning state, and emits finished() .

Example:

...
progressBar = QProgressBar(self)
progressBar.setRange(0, 100)
# Construct a 1-second timeline with a frame range of 0 - 100
timeLine = QTimeLine(1000, self)
timeLine.setFrameRange(0, 100)
connect(timeLine, QTimeLine.frameChanged, progressBar, QProgressBar.setValue)
# Clicking the push button will start the progress bar animation
pushButton = QPushButton(tr("Start animation"), self)
connect(pushButton, QPushButton.clicked, timeLine, QTimeLine.start)
...

By default the timeline runs once, from its beginning to its end, upon which you must call start() again to restart from the beginning. To make the timeline loop, you can call setLoopCount() , passing the number of times the timeline should run before finishing. The direction can also be changed, causing the timeline to run backward, by calling setDirection() . You can also pause and unpause the timeline while it’s running by calling setPaused() . For interactive control, the setCurrentTime() function is provided, which sets the time position of the time line directly. Although most useful in NotRunning state (e.g., connected to a valueChanged() signal in a QSlider ), this function can be called at any time.

The frame interface is useful for standard widgets, but QTimeLine can be used to control any type of animation. The heart of QTimeLine lies in the valueForTime() function, which generates a value between 0 and 1 for a given time. This value is typically used to describe the steps of an animation, where 0 is the first step of an animation, and 1 is the last step. When running, QTimeLine generates values between 0 and 1 by calling valueForTime() and emitting valueChanged() . By default, valueForTime() applies an interpolation algorithm to generate these value. You can choose from a set of predefined timeline algorithms by calling setEasingCurve() .

Note that, by default, QTimeLine uses InOutSine , which provides a value that grows slowly, then grows steadily, and finally grows slowly. For a custom timeline, you can reimplement valueForTime() , in which case QTimeLine ‘s easingCurve property is ignored.

See also

QProgressBar QProgressDialog

class PySide6.QtCore.QTimeLine([duration=1000[, parent=None]])
Parameters

Constructs a timeline with a duration of duration milliseconds. parent is passed to QObject ‘s constructor. The default duration is 1000 milliseconds.

PySide6.QtCore.QTimeLine.State

This enum describes the state of the timeline.

Constant

Description

QTimeLine.NotRunning

The timeline is not running. This is the initial state of QTimeLine , and the state QTimeLine reenters when finished. The current time, frame and value remain unchanged until either setCurrentTime() is called, or the timeline is started by calling start() .

QTimeLine.Paused

The timeline is paused (i.e., temporarily suspended). Calling setPaused (false) will resume timeline activity.

QTimeLine.Running

The timeline is running. While control is in the event loop, QTimeLine will update its current time at regular intervals, emitting valueChanged() and frameChanged() when appropriate.

See also

state() stateChanged()

PySide6.QtCore.QTimeLine.Direction

This enum describes the direction of the timeline when in Running state.

Constant

Description

QTimeLine.Forward

The current time of the timeline increases with time (i.e., moves from 0 and towards the end / duration).

QTimeLine.Backward

The current time of the timeline decreases with time (i.e., moves from the end / duration and towards 0).

See also

setDirection()

PySide6.QtCore.QTimeLine.currentFrame()
Return type

int

Returns the frame corresponding to the current time.

PySide6.QtCore.QTimeLine.currentTime()
Return type

int

This property holds the current time of the time line..

When QTimeLine is in Running state, this value is updated continuously as a function of the duration and direction of the timeline. Otherwise, it is value that was current when stop() was called last, or the value set by .

Note

You can bind other properties to , but it is not recommended setting bindings to it. As animation progresses, the is updated automatically, which cancels its bindings.

By default, this property contains a value of 0.

PySide6.QtCore.QTimeLine.currentValue()
Return type

float

Returns the value corresponding to the current time.

PySide6.QtCore.QTimeLine.direction()
Return type

Direction

This property holds the direction of the timeline when QTimeLine is in Running state..

This direction indicates whether the time moves from 0 towards the timeline duration, or from the value of the duration and towards 0 after start() has been called.

Any binding of direction will be removed not only by , but also by toggleDirection() .

By default, this property is set to Forward .

PySide6.QtCore.QTimeLine.duration()
Return type

int

This property holds the total duration of the timeline in milliseconds..

By default, this value is 1000 (i.e., 1 second), but you can change this by either passing a duration to QTimeLine ‘s constructor, or by calling . The duration must be larger than 0.

Note

Changing the duration does not cause the current time to be reset to zero or the new duration. You also need to call setCurrentTime() with the desired value.

PySide6.QtCore.QTimeLine.easingCurve()
Return type

PySide6.QtCore.QEasingCurve

Specifies the easing curve that the timeline will use. If valueForTime() is reimplemented, this value is ignored.

See also

valueForTime()

PySide6.QtCore.QTimeLine.endFrame()
Return type

int

Returns the end frame, which is the frame corresponding to the end of the timeline (i.e., the frame for which the current value is 1).

PySide6.QtCore.QTimeLine.frameForTime(msec)
Parameters

msec – int

Return type

int

Returns the frame corresponding to the time msec. This value is calculated using a linear interpolation of the start and end frame, based on the value returned by valueForTime() .

PySide6.QtCore.QTimeLine.loopCount()
Return type

int

This property holds the number of times the timeline should loop before it’s finished..

A loop count of of 0 means that the timeline will loop forever.

By default, this property contains a value of 1.

PySide6.QtCore.QTimeLine.resume()

Resumes the timeline from the current time. QTimeLine will reenter Running state, and once it enters the event loop, it will update its current time, frame and value at regular intervals.

In contrast to start() , this function does not restart the timeline before it resumes.

See also

start() updateInterval() frameChanged() valueChanged()

PySide6.QtCore.QTimeLine.setCurrentTime(msec)
Parameters

msec – int

This property holds the current time of the time line..

When QTimeLine is in Running state, this value is updated continuously as a function of the duration and direction of the timeline. Otherwise, it is value that was current when stop() was called last, or the value set by .

Note

You can bind other properties to , but it is not recommended setting bindings to it. As animation progresses, the is updated automatically, which cancels its bindings.

By default, this property contains a value of 0.

PySide6.QtCore.QTimeLine.setDirection(direction)
Parameters

direction – Direction

This property holds the direction of the timeline when QTimeLine is in Running state..

This direction indicates whether the time moves from 0 towards the timeline duration, or from the value of the duration and towards 0 after start() has been called.

Any binding of direction will be removed not only by , but also by toggleDirection() .

By default, this property is set to Forward .

PySide6.QtCore.QTimeLine.setDuration(duration)
Parameters

duration – int

This property holds the total duration of the timeline in milliseconds..

By default, this value is 1000 (i.e., 1 second), but you can change this by either passing a duration to QTimeLine ‘s constructor, or by calling . The duration must be larger than 0.

Note

Changing the duration does not cause the current time to be reset to zero or the new duration. You also need to call setCurrentTime() with the desired value.

PySide6.QtCore.QTimeLine.setEasingCurve(curve)
Parameters

curve – PySide6.QtCore.QEasingCurve

Specifies the easing curve that the timeline will use. If valueForTime() is reimplemented, this value is ignored.

See also

valueForTime()

PySide6.QtCore.QTimeLine.setEndFrame(frame)
Parameters

frame – int

Sets the end frame, which is the frame corresponding to the end of the timeline (i.e., the frame for which the current value is 1), to frame.

PySide6.QtCore.QTimeLine.setFrameRange(startFrame, endFrame)
Parameters

  • startFrame – int

  • endFrame – int

Sets the timeline’s frame counter to start at startFrame, and end and endFrame. For each time value, QTimeLine will find the corresponding frame when you call currentFrame() or frameForTime() by interpolating, using the return value of valueForTime() .

When in Running state, QTimeLine also emits the frameChanged() signal when the frame changes.

PySide6.QtCore.QTimeLine.setLoopCount(count)
Parameters

count – int

This property holds the number of times the timeline should loop before it’s finished..

A loop count of of 0 means that the timeline will loop forever.

By default, this property contains a value of 1.

PySide6.QtCore.QTimeLine.setPaused(paused)
Parameters

paused – bool

If paused is true, the timeline is paused, causing QTimeLine to enter Paused state. No updates will be signaled until either start() or (false) is called. If paused is false, the timeline is resumed and continues where it left.

See also

state() start()

PySide6.QtCore.QTimeLine.setStartFrame(frame)
Parameters

frame – int

Sets the start frame, which is the frame corresponding to the start of the timeline (i.e., the frame for which the current value is 0), to frame.

PySide6.QtCore.QTimeLine.setUpdateInterval(interval)
Parameters

interval – int

This property holds the time in milliseconds between each time QTimeLine updates its current time..

When updating the current time, QTimeLine will emit valueChanged() if the current value changed, and frameChanged() if the frame changed.

By default, the interval is 40 ms, which corresponds to a rate of 25 updates per second.

PySide6.QtCore.QTimeLine.start()

Starts the timeline. QTimeLine will enter Running state, and once it enters the event loop, it will update its current time, frame and value at regular intervals. The default interval is 40 ms (i.e., 25 times per second). You can change the update interval by calling setUpdateInterval() .

The timeline will start from position 0, or the end if going backward. If you want to resume a stopped timeline without restarting, you can call resume() instead.

See also

resume() updateInterval() frameChanged() valueChanged()

PySide6.QtCore.QTimeLine.startFrame()
Return type

int

Returns the start frame, which is the frame corresponding to the start of the timeline (i.e., the frame for which the current value is 0).

PySide6.QtCore.QTimeLine.state()
Return type

State

Returns the state of the timeline.

PySide6.QtCore.QTimeLine.stop()

Stops the timeline, causing QTimeLine to enter NotRunning state.

See also

start()

PySide6.QtCore.QTimeLine.toggleDirection()

Toggles the direction of the timeline. If the direction was Forward, it becomes Backward, and vice verca.

Existing bindings of direction are removed.

See also

setDirection()

PySide6.QtCore.QTimeLine.updateInterval()
Return type

int

This property holds the time in milliseconds between each time QTimeLine updates its current time..

When updating the current time, QTimeLine will emit valueChanged() if the current value changed, and frameChanged() if the frame changed.

By default, the interval is 40 ms, which corresponds to a rate of 25 updates per second.

PySide6.QtCore.QTimeLine.valueForTime(msec)
Parameters

msec – int

Return type

float

Returns the timeline value for the time msec. The returned value, which varies depending on the curve shape, is always between 0 and 1. If msec is 0, the default implementation always returns 0.

Reimplement this function to provide a custom curve shape for your timeline.