/// <summary>
/// Reads data from the world grid. Not done in the constructor to allow callers to subscribe to
/// the events that will be fired.
/// </summary>
/// <param name="position"> The position. </param>
public void Initialize(GridCoordinate position)
{
_currentPosition = position;
_viewCurrentPosition = ConvertToGridItemIndex(position);
InitializeUnits();
}
/// <summary>
/// Converts the given grid coordinate into a an index that can be used to get the data in
/// <see cref="_visibleGridItems"/>.
/// </summary>
/// <remarks>
/// Multiple GridCoordinates map to the same ArrayIndex, so this is technically an irreversible
/// operation. However, provided we always remain within the correct GridCoordinates (e.g. always
/// use grid coordinates that we generate or which are validated first), we should never really
/// have a situation where a conversion to an array index and back results in a different
/// coordinate.
/// </remarks>
/// <param name="coordinate"> The coordinate. </param>
/// <returns> The given data converted to a grid item index. </returns>
private Array2DIndex ConvertToGridItemIndex(GridCoordinate coordinate)
{
var correctedX = MathUtils.PositiveRemainder(coordinate.X, _visibleGridItems.Width);
var correctedY = MathUtils.PositiveRemainder(coordinate.Y, _visibleGridItems.Height);
var arrayIndex = new Array2DIndex(correctedX, correctedY);
return(arrayIndex);
}
/// <summary> Changes the position being observed. </summary>
public void Recenter(GridCoordinate center)
{
var originalPosition = _currentPosition;
_currentPosition = center;
_viewCurrentPosition = ConvertToGridItemIndex(_currentPosition);
UpdateChangedUnits(originalPosition);
}
/// <summary> Updates the data at the specified index inside the grid. </summary>
/// <param name="index"> Zero-based index of the. </param>
/// <param name="data"> The grid data to store. </param>
/// <param name="position"> The coordinate of the original GridItem where the data was retrieved
/// from. </param>
/// <param name="chunk"></param>
private void UpdateData(Array2DIndex index, GridItem data, GridCoordinate position, Chunk chunk)
{
var newData = new SliceUnitData <T>(chunk, position, data, default(T));
var rawIndex = _visibleGridItems.CalculateRawArrayIndex(index);
var oldData = _visibleGridItems.Data[rawIndex];
_visibleGridItems.Data[rawIndex] = newData;
DataChanged?.Invoke(oldData, ref _visibleGridItems.Data[rawIndex]);
MarkChunkChanged(oldData.Chunk, chunk);
}
/// <summary>
/// Converts an array index into the expected grid coordinate for the given index.
/// </summary>
/// <param name="arrayIndex"> Zero-based index of the array. </param>
/// <returns> The given data converted to a grid coordinate. </returns>
private GridCoordinate ConvertToGridCoordinate(Array2DIndex arrayIndex)
{
var difViewX = _viewCurrentPosition.X - arrayIndex.X;
var signX = GetSign(difViewX);
// Normalize the offset from the "current" view position.
//
// This explanation just talks about X, the same theory holds for Y. Imagine a number line
// ranging from 0 to maxViewX).
//
// If the current position is on the right (so it's position is maxViewX), then the very left
// position (position 0) of the view really just represents one world unit to the right of the
// current position. If we simply subtracted these two positions, however, it would be
// reported it as a difference of -ViewWidth units away We want to convert it to a difference
// of (1).
//
// We know we have to do convert values if it's more than half the size away (that's the only
// time that wrapping occurs when putting the values into the view). The conversion is fairly
// straight forward when given examples:
// - When we're `maxViewX` view units away, we're really only 1 world unit away.
// - When we're `maxViewX - 1` units away we're really only 2 world units away.
// - When we're `maxViewX - N` units away, we're really only N world units away.
//
// The pattern to find N (the world units away) is to take `ViewWidth` and "subtract"
// `(maxViewX - N)`. `maxViewX - N` happens to be diffViewX, so then we just have to "subtract"
// it from `ViewWidth`. "subtract" is in quotes because actually, when the difference is
// negative, we want to add `ViewWidth` (otherwise we end up in very negative territory). So we
// add when `maxViewX - N` is negative, subtract when `maxViewX - N` is positive.
var offsetX = Math.Abs(difViewX) > _numUnitsWideHalfThreshold
? difViewX + -signX * _visibleGridItems.Width
: difViewX;
// all of the above but now for Y
var difViewY = _viewCurrentPosition.Y - arrayIndex.Y;
var signY = difViewY >= 0 ? 1 : -1;
var offsetY = Math.Abs(difViewY) > _numUnitsHighHalfThreshold
? difViewY + -signY * _visibleGridItems.Height
: difViewY;
var gridPosition = _currentPosition.OffsetBy(-offsetX, -offsetY);
ValidateConversion(gridPosition, arrayIndex);
return(gridPosition);
}
/// <summary> Initialize each grid unit. </summary>
private void InitializeUnits()
{
for (var y = 0; y < _visibleGridItems.Height; y++)
{
for (var x = 0; x < _visibleGridItems.Width; x++)
{
var index = new Array2DIndex(x, y);
var coordinate = ConvertToGridCoordinate(index);
var subCoordinates = coordinate.AsSubCoordinates();
if (_worldGrid.IsValid(subCoordinates.ChunkCoordinate))
{
var(chunk, data) = _worldGrid.GetChunkAndCellData(subCoordinates);
UpdateData(index, data, coordinate, chunk, GridItemPropertyChange.All);
}
}
}
}
/// <summary>
/// Checks the array index/position to verify that it has the correct position information and if
/// it does not, re-reads the data from the world and updates the data.
/// </summary>
private void Invalidate(Array2DIndex index, GridCoordinate coordinate, bool bypassSamePositionCheck, GridItemPropertyChange changeType)
{
var existingData = _visibleGridItems[index];
if (!bypassSamePositionCheck && existingData.Position == coordinate)
{
return;
}
var subCoordinate = coordinate.AsSubCoordinates();
if (!_worldGrid.IsValid(subCoordinate.ChunkCoordinate))
{
return;
}
var(chunk, data) = _worldGrid.GetChunkAndCellData(subCoordinate);
UpdateData(index, data, coordinate, chunk, changeType);
}
/// <summary> Initialize each grid unit. </summary>
private void InitializeUnits()
{
for (var y = 0; y < _visibleGridItems.Height; y++)
{
for (var x = 0; x < _visibleGridItems.Width; x++)
{
var index = new Array2DIndex(x, y);
var coordinate = ConvertToGridCoordinate(index);
var chunkCoordinate = coordinate.ChunkCoordinate;
if (_worldGrid.IsValid(chunkCoordinate))
{
var chunk = _worldGrid[chunkCoordinate];
var data = chunk[coordinate.InnerChunkGridCoordinate];
UpdateData(index, data, coordinate, chunk);
}
}
}
}
/// <summary>
/// Checks the array index/position to verify that it has the correct position information and if
/// it does not, re-reads the data from the world and updates the data.
/// </summary>
/// <param name="index"> The index position to update. </param>
/// <param name="coordinate"> The coordinate representing the position to update. </param>
private void Invalidate(Array2DIndex index, GridCoordinate coordinate, bool bypassSamePositionCheck = false)
{
var existingData = _visibleGridItems[index];
if (!bypassSamePositionCheck && existingData.Position == coordinate)
{
return;
}
var chunkCoordinate = coordinate.ChunkCoordinate;
if (!_worldGrid.IsValid(chunkCoordinate))
{
return;
}
var chunk = _worldGrid[chunkCoordinate];
var data = chunk[coordinate.InnerChunkGridCoordinate];
UpdateData(index, data, coordinate, chunk);
}
private void ValidateConversion(GridCoordinate gridPosition, Array2DIndex arrayIndex)
{
var worked = ConvertToGridItemIndex(gridPosition).X == arrayIndex.X &&
ConvertToGridItemIndex(gridPosition).Y == arrayIndex.Y;
if (worked)
{
return;
}
// to aid in debugging
worked = ConvertToGridItemIndex(gridPosition).X == arrayIndex.X &&
ConvertToGridItemIndex(gridPosition).Y == arrayIndex.Y;
var message = new StringBuilder();
message.AppendFormat("Array Index ({0}) was converted into Grid Position ({1})", arrayIndex, gridPosition);
message.AppendFormat("But we expected ({0},{1})",
ConvertToGridItemIndex(gridPosition).X,
ConvertToGridItemIndex(gridPosition).Y);
Debug.WriteLine(message);
}
/// <summary> Updates the data at the specified index inside the grid. </summary>
/// <param name="index"> Zero-based index of the. </param>
/// <param name="data"> The grid data to store. </param>
/// <param name="position"> The coordinate of the original GridItem where the data was retrieved
/// from. </param>
/// <param name="chunk"></param>
/// <param name="changeType"></param>
private void UpdateData(Array2DIndex index, GridItem data, GridCoordinate position, Chunk chunk, GridItemPropertyChange changeType)
{
var newData = new SliceUnitData <T>(chunk, position, data, default(T));
var rawIndex = _visibleGridItems.CalculateRawArrayIndex(index);
ref var slot = ref _visibleGridItems.Data[rawIndex];
private void Invalidate(Array2DIndex index, GridCoordinate coordinate) => Invalidate(index, coordinate, bypassSamePositionCheck: false, changeType: GridItemPropertyChange.All);
/// <summary>
/// Checks the array index/position to verify that it has the correct position information and if
/// it does not, re-reads the data from the world and updates the data.
/// </summary>
/// <param name="index"> The index position to update. </param>
private void InvalidateIndex(Array2DIndex index)
{
Invalidate(index, ConvertToGridCoordinate(index));
}