Summary:
The redirect modes control behavior of the timeline when its direction
is changed at the start or target position. For example, consider the
following piece of code:
TimeLine timeLine(1000ms, TimeLine::Forward);
timeLine.setDirection(TimeLine::Backward);
What should happen when the direction of the timeline was changed to go
backward? Should the current value of the timeline go from 1 to 0, or
should the timeline stop its "execution"?
In the relaxed mode, the timeline will go from 1 to 0.
In the strict mode, the timeline will stop its execution.
Different effects may prefer different modes for source and target
positions. For example, most C++ effect would prefer relaxed mode for
source position, and strict mode for target position. On the other side,
scripted effects(AnimationEffect) would prefer strict mode for source
position, and relaxed mode for target position(because of set).
Reviewers: #kwin, graesslin
Reviewed By: #kwin, graesslin
Subscribers: kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D16447
Summary:
Most effects use QTimeLine in the following manner
```lang=cpp
if (...) {
m_timeline->setCurrentTime(m_timeline->currentTime() + time);
} else {
m_timeline->setCurrentTime(m_timeline->currentTime() - time);
}
```
Because effects do not rely on a timer that QTimeLine has, they can't
toggle direction of the QTimeLine, which makes somewhat harder to write
effects. In some cases that's obvious what condition to use to figure
out whether to add or subtract `time`, but there are cases when it's
not. In addition to that, setCurrentTime allows to have negative
currentTime, which in some cases causes bugs.
And overall, the way effects use QTimeLine is really hack-ish. It makes
more sense just to use an integer accumulator(like the Fall Apart
effect is doing) than to use QTimeLine.
Another problem with QTimeLine is that it's a QObject and some effects
do
```lang=cpp
class WindowInfo
{
public:
~WindowInfo();
QTimeLine *timeLine;
};
WindowInfo::~WindowInfo()
{
delete timeLine;
}
// ...
QHash<EffectWindow*, WindowInfo> m_windows;
```
which is unsafe.
This change adds the TimeLine class. The TimeLine class is a timeline
helper that designed specifically for needs of effects.
Demo
```lang=cpp
TimeLine timeLine(1000, TimeLine::Forward);
timeLine.setEasingCurve(QEasingCurve::Linear);
timeLine.value(); // 0.0
timeLine.running(); // false
timeLine.done(); // false
timeLine.update(420);
timeLine.value(); // 0.42
timeLine.running(); // true
timeLine.done(); // false
timeLine.toggleDirection();
timeLine.value(); // 0.42
timeLine.running(); // true
timeLine.done(); // false
timeLine.update(100);
timeLine.value(); // 0.32
timeLine.running(); // true
timeLine.done(); // false
timeLine.update(1000);
timeLine.value(); // 0.0
timeLine.running(); // false
timeLine.done(); // true
```
Test Plan: Ran tests.
Reviewers: #kwin, davidedmundson, graesslin
Reviewed By: #kwin, davidedmundson, graesslin
Subscribers: romangg, graesslin, anthonyfieroni, davidedmundson, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D13740
