/// <summary>
/// Creation of an expression to manage modulo (positive and negative value)
/// </summary>
/// <param name="scrollViewer">The ScrollViewer to synchronized. A null value is valid</param>
/// <param name="imageWidth">Width of the image</param>
/// <param name="imageHeight">Height of the image</param>
/// <param name="scrollOrientation">The ScrollOrientation</param>
private void CreateModuloExpression(ScrollViewer scrollViewer, double imageWidth, double imageHeight, ScrollOrientation scrollOrientation)
{
const string offsetXParam = "offsetX";
const string offsetYParam = "offsetY";
const string imageWidthParam = "imageWidth";
const string imageHeightParam = "imageHeight";
const string speedParam = "speed";
if (_containerVisual == null)
{
return;
}
var compositor = _containerVisual.Compositor;
// Setup the expression
ExpressionNode expressionX = null;
ExpressionNode expressionY = null;
ExpressionNode expressionXVal;
ExpressionNode expressionYVal;
var propertySetModulo = compositor.CreatePropertySet();
propertySetModulo.InsertScalar(imageWidthParam, (float)imageWidth);
propertySetModulo.InsertScalar(offsetXParam, (float)OffsetX);
propertySetModulo.InsertScalar(imageHeightParam, (float)imageHeight);
propertySetModulo.InsertScalar(offsetYParam, (float)OffsetY);
propertySetModulo.InsertScalar(speedParam, (float)ParallaxSpeedRatio);
var propertySetNodeModulo = propertySetModulo.GetReference();
var imageHeightNode = propertySetNodeModulo.GetScalarProperty(imageHeightParam);
var imageWidthNode = propertySetNodeModulo.GetScalarProperty(imageWidthParam);
if (scrollViewer == null)
{
var offsetXNode = ExpressionFunctions.Ceil(propertySetNodeModulo.GetScalarProperty(offsetXParam));
var offsetYNode = ExpressionFunctions.Ceil(propertySetNodeModulo.GetScalarProperty(offsetYParam));
// expressions are created to simulate a positive and negative modulo with the size of the image and the offset
expressionXVal = ExpressionFunctions.Conditional(
offsetXNode == 0,
0,
ExpressionFunctions.Conditional(
offsetXNode < 0,
-(ExpressionFunctions.Abs(offsetXNode - (ExpressionFunctions.Ceil(offsetXNode / imageWidthNode) * imageWidthNode)) % imageWidthNode),
-(imageWidthNode - (offsetXNode % imageWidthNode))));
expressionYVal = ExpressionFunctions.Conditional(
offsetYNode == 0,
0,
ExpressionFunctions.Conditional(
offsetYNode < 0,
-(ExpressionFunctions.Abs(offsetYNode - (ExpressionFunctions.Ceil(offsetYNode / imageHeightNode) * imageHeightNode)) % imageHeightNode),
-(imageHeightNode - (offsetYNode % imageHeightNode))));
}
else
{
// expressions are created to simulate a positive and negative modulo with the size of the image and the offset and the ScrollViewer offset (Translation)
var scrollProperties = ElementCompositionPreview.GetScrollViewerManipulationPropertySet(scrollViewer);
var scrollPropSet = scrollProperties.GetSpecializedReference <ManipulationPropertySetReferenceNode>();
var speed = propertySetNodeModulo.GetScalarProperty(speedParam);
var xCommon = ExpressionFunctions.Ceil((scrollPropSet.Translation.X * speed) + propertySetNodeModulo.GetScalarProperty(offsetXParam));
expressionXVal = ExpressionFunctions.Conditional(
xCommon == 0,
0,
ExpressionFunctions.Conditional(
xCommon < 0,
-(ExpressionFunctions.Abs(xCommon - (ExpressionFunctions.Ceil(xCommon / imageWidthNode) * imageWidthNode)) % imageWidthNode),
-(imageWidthNode - (xCommon % imageWidthNode))));
var yCommon = ExpressionFunctions.Ceil((scrollPropSet.Translation.Y * speed) + propertySetNodeModulo.GetScalarProperty(offsetYParam));
expressionYVal = ExpressionFunctions.Conditional(
yCommon == 0,
0,
ExpressionFunctions.Conditional(
yCommon < 0,
-(ExpressionFunctions.Abs(yCommon - (ExpressionFunctions.Ceil(yCommon / imageHeightNode) * imageHeightNode)) % imageHeightNode),
-(imageHeightNode - (yCommon % imageHeightNode))));
}
if (scrollOrientation == ScrollOrientation.Horizontal || scrollOrientation == ScrollOrientation.Both)
{
expressionX = expressionXVal;
if (scrollOrientation == ScrollOrientation.Horizontal)
{
// In horizontal mode we never move the offset y
expressionY = (ScalarNode)0.0f;
_containerVisual.Offset = new Vector3((float)OffsetY, 0, 0);
}
}
if (scrollOrientation == ScrollOrientation.Vertical || scrollOrientation == ScrollOrientation.Both)
{
expressionY = expressionYVal;
if (scrollOrientation == ScrollOrientation.Vertical)
{
// In vertical mode we never move the offset x
expressionX = (ScalarNode)0.0f;
_containerVisual.Offset = new Vector3(0, (float)OffsetX, 0);
}
}
_containerVisual.StopAnimation("Offset.X");
_containerVisual.StopAnimation("Offset.Y");
_containerVisual.StartAnimation("Offset.X", expressionX);
_containerVisual.StartAnimation("Offset.Y", expressionY);
_propertySetModulo = propertySetModulo;
}
