public void SetHorizontalOffset(double offset)
{
if (offset < 0 || this.viewport.Width >= this.extent.Width)
{
offset = 0;
}
else if (offset + this.viewport.Width >= this.extent.Width)
{
offset = this.extent.Width - this.viewport.Width;
}
this.contentOffset.X = offset;
if (usingCustomScrolling)
{
this.horizontalBackend.SetOffset(offset);
}
else
{
this.transform.X = -offset;
}
if (ScrollOwner != null)
{
ScrollOwner.InvalidateScrollInfo();
}
}
private void SetViewport(Size size)
{
if (_viewport != size)
{
_viewport = size;
if (_owner != null)
{
_owner.InvalidateScrollInfo();
}
}
}
void SetOffset(double?x = null, double?y = null)
{
var offset = this.contentOffset;
if (x.HasValue)
{
offset.X = x.Value;
}
if (y.HasValue)
{
offset.Y = y.Value;
}
// Clamp horizontal
if (offset.X < 0 || this.viewport.Width >= this.extent.Width)
{
offset.X = 0;
}
else if (offset.X + this.viewport.Width >= this.extent.Width)
{
offset.X = this.extent.Width - this.viewport.Width;
}
// Clamp vertical
if (offset.Y < 0 || this.viewport.Height >= this.extent.Height)
{
offset.Y = 0;
}
else if (offset.Y + this.viewport.Height >= this.extent.Height)
{
offset.Y = this.extent.Height - this.viewport.Height;
}
if (offset != this.contentOffset)
{
this.contentOffset = offset;
if (usingCustomScrolling)
{
this.horizontalBackend.SetOffset(offset.X);
this.verticalBackend.SetOffset(offset.Y);
}
else
{
this.transform.X = -offset.X;
this.transform.Y = -offset.Y;
}
if (ScrollOwner != null)
{
ScrollOwner.InvalidateScrollInfo();
}
}
}
// OnScrollChange is an override called whenever the IScrollInfo exposed scrolling state changes on this element.
// At the time this method is called, scrolling state is in its new, valid state.
private void OnScrollChange()
{
if (ScrollOwner != null)
{
ScrollOwner.InvalidateScrollInfo();
}
}