getDestinationRect function

Rect getDestinationRect (
  1. {@required Rect rect,
  2. @required Size inputSize,
  3. double scale: 1.0,
  4. BoxFit fit,
  5. Alignment alignment: Alignment.center,
  6. Rect centerSlice,
  7. bool flipHorizontally: false}
)

Implementation

Rect getDestinationRect({
  @required Rect rect,
  @required Size inputSize,
  double scale = 1.0,
  BoxFit fit,
  Alignment alignment = Alignment.center,
  Rect centerSlice,
  bool flipHorizontally = false,
}) {
  Size outputSize = rect.size;

  Offset sliceBorder;
  if (centerSlice != null) {
    sliceBorder = Offset(centerSlice.left + inputSize.width - centerSlice.right,
        centerSlice.top + inputSize.height - centerSlice.bottom);
    outputSize = outputSize - sliceBorder as Size;
    inputSize = inputSize - sliceBorder as Size;
  }
  fit ??= centerSlice == null ? BoxFit.scaleDown : BoxFit.fill;
  assert(centerSlice == null || (fit != BoxFit.none && fit != BoxFit.cover));
  final FittedSizes fittedSizes =
      applyBoxFit(fit, inputSize / scale, outputSize);
  final Size sourceSize = fittedSizes.source * scale;
  Size destinationSize = fittedSizes.destination;
  if (centerSlice != null) {
    outputSize += sliceBorder;
    destinationSize += sliceBorder;
    // We don't have the ability to draw a subset of the image at the same time
    // as we apply a nine-patch stretch.
    assert(sourceSize == inputSize,
        'centerSlice was used with a BoxFit that does not guarantee that the image is fully visible.');
  }

  final double halfWidthDelta =
      (outputSize.width - destinationSize.width) / 2.0;
  final double halfHeightDelta =
      (outputSize.height - destinationSize.height) / 2.0;
  final double dx = halfWidthDelta +
      (flipHorizontally ? -alignment.x : alignment.x) * halfWidthDelta;
  final double dy = halfHeightDelta + alignment.y * halfHeightDelta;
  final Offset destinationPosition = rect.topLeft.translate(dx, dy);
  final Rect destinationRect = destinationPosition & destinationSize;

  // final Rect sourceRect =
  //     centerSlice ?? alignment.inscribe(sourceSize, Offset.zero & inputSize);

  return destinationRect;
}