float _calculateScrollIncrement(ScrollableState state, ScrollIncrementType type = ScrollIncrementType.line)
{
D.assert(state.position != null);
D.assert(state.position.havePixels);
D.assert(state.widget.physics == null || state.widget.physics.shouldAcceptUserOffset(state.position));
if (state.widget.incrementCalculator != null)
{
return(state.widget.incrementCalculator(
new ScrollIncrementDetails(
type: type,
metrics: state.position
)
));
}
switch (type)
{
case ScrollIncrementType.line:
return(50.0f);
case ScrollIncrementType.page:
return(0.8f * state.position.viewportDimension);
}
return(0.0f);
}
public ScrollIntent(
AxisDirection direction,
ScrollIncrementType type = ScrollIncrementType.line
) : base(ScrollAction.key)
{
this.direction = direction;
this.type = type;
}
public ScrollIncrementDetails(
ScrollIncrementType type,
ScrollMetrics metrics
)
{
D.assert(metrics != null);
this.type = type;
this.metrics = metrics;
}