/// <summary>
/// Optimizes the rectangle's placement by moving it either left or up to fill
/// any gaps resulting from rectangles blocking the anchors of the most optimal
/// placements.
/// </summary>
/// <param name="placement">Placement to be optimized</param>
/// <param name="rectangleWidth">Width of the rectangle to be optimized</param>
/// <param name="rectangleHeight">Height of the rectangle to be optimized</param>
private void OptimizePlacement(ref Pointi placement, int rectangleWidth, int rectangleHeight)
{
var rectangle = Recti.FromSize(placement.X, placement.Y, rectangleWidth, rectangleHeight);
// Try to move the rectangle to the left as far as possible
int leftMost = placement.X;
while (IsFree(ref rectangle, PackingAreaWidth, PackingAreaHeight))
{
leftMost = rectangle.X;
--rectangle.X;
}
// Reset rectangle to original position
rectangle.X = placement.X;
// Try to move the rectangle upwards as far as possible
int topMost = placement.Y;
while (IsFree(ref rectangle, PackingAreaWidth, PackingAreaHeight))
{
topMost = rectangle.Y;
--rectangle.Y;
}
// Use the dimension in which the rectangle could be moved farther
if ((placement.X - leftMost) > (placement.Y - topMost))
{
placement.X = leftMost;
}
else
{
placement.Y = topMost;
}
}
/// <summary>Tries to allocate space for a rectangle in the packing area</summary>
/// <param name="rectangleWidth">Width of the rectangle to allocate</param>
/// <param name="rectangleHeight">Height of the rectangle to allocate</param>
/// <param name="placement">Output parameter receiving the rectangle's placement</param>
/// <returns>True if space for the rectangle could be allocated</returns>
public override bool TryPack(int rectangleWidth, int rectangleHeight, out Pointi placement)
{
// Try to find an anchor where the rectangle fits in, enlarging the packing
// area and repeating the search recursively until it fits or the
// maximum allowed size is exceeded.
int anchorIndex = SelectAnchorRecursive(rectangleWidth, rectangleHeight, actualPackingAreaWidth, actualPackingAreaHeight);
// No anchor could be found at which the rectangle did fit in
if (anchorIndex == -1)
{
placement = new Pointi();
return(false);
}
placement = anchors[anchorIndex];
// Move the rectangle either to the left or to the top until it collides with
// a neightbouring rectangle. This is done to combat the effect of lining up
// rectangles with gaps to the left or top of them because the anchor that
// would allow placement there has been blocked by another rectangle
OptimizePlacement(ref placement, rectangleWidth, rectangleHeight);
// Remove the used anchor and add new anchors at the upper right and lower left
// positions of the new rectangle
// The anchor is only removed if the placement optimization didn't
// move the rectangle so far that the anchor isn't blocked anymore
bool blocksAnchor =
((placement.X + rectangleWidth) > anchors[anchorIndex].X) &&
((placement.Y + rectangleHeight) > anchors[anchorIndex].Y);
if (blocksAnchor)
{
anchors.RemoveAt(anchorIndex);
}
// Add new anchors at the upper right and lower left coordinates of the rectangle
InsertAnchor(new Pointi(placement.X + rectangleWidth, placement.Y));
InsertAnchor(new Pointi(placement.X, placement.Y + rectangleHeight));
// Finally, we can add the rectangle to our packed rectangles list
packedRectangles.Add(Recti.FromSize(placement.X, placement.Y, rectangleWidth, rectangleHeight));
return(true);
}
/// <summary>Inserts a new anchor point into the anchor list</summary>
/// <param name="anchor">Anchor point that will be inserted</param>
/// <remarks>
/// This method tries to keep the anchor list ordered by ranking the anchors
/// depending on the distance from the top left corner in the packing area.
/// </remarks>
private void InsertAnchor(Pointi anchor)
{
// Find out where to insert the new anchor based on its rank (which is
// calculated based on the anchor's distance to the top left corner of
// the packing area).
//
// From MSDN on BinarySearch():
// "If the List does not contain the specified value, the method returns
// a negative integer. You can apply the bitwise complement operation (~) to
// this negative integer to get the index of the first element that is
// larger than the search value."
int insertIndex = anchors.BinarySearch(anchor, AnchorRankComparer.Default);
if (insertIndex < 0)
{
insertIndex = ~insertIndex;
}
// Insert the anchor at the index matching its rank
anchors.Insert(insertIndex, anchor);
}
/// <summary>Tries to allocate space for a rectangle in the packing area</summary> /// <param name="rectangleWidth">Width of the rectangle to allocate</param> /// <param name="rectangleHeight">Height of the rectangle to allocate</param> /// <param name="placement">Output parameter receiving the rectangle's placement</param> /// <returns>True if space for the rectangle could be allocated</returns> public abstract bool TryPack(int rectangleWidth, int rectangleHeight, out Pointi placement);