getEffectiveChildSizeForImage function

SizeC getEffectiveChildSizeForImage(BaseNode node, PaintModel paint, { double? scaleX, double? scaleY, })

Get effective child size for image position calculation for rendering alignment overlay for images.

Except for fitWidth and fitHeight, it returns child size calculated based on the alignment and image scale.

However, if image fit is fitWidth or fitHeight, image is scaled internally regardless of given PaintModel.scaleX/PaintModel.scaleY value to fit either on width or height. Since this is internal, we need to account for it because the effective width and child height are no longer depend on given PaintModel.scaleX/PaintModel.scaleY value. For this case, we manually calculate the effective child size by calculating the linear scale factor based on node size and image aspect ratio.

This method must be called before calling convertAlignmentToPosition and convertPositionToAlignment to get the correct childWidth and childHeight for these methods.

Implementation

SizeC getEffectiveChildSizeForImage(BaseNode node, PaintModel paint,
    {double? scaleX, double? scaleY}) {
  final double modifiedScaleX = (scaleX ?? paint.scaleX).abs();
  final double modifiedScaleY = (scaleY ?? paint.scaleY).abs();

  final double width;
  if (paint.fit == Fit.fitWidth) {
    width = node.middleBoxGlobal.width;
  } else if (paint.fit == Fit.fitHeight && paint.hasImageSourceSize) {
    final aspectRatio = paint.sourceWidth! / paint.sourceHeight!;
    width = aspectRatio * node.middleBoxGlobal.height;
  } else {
    width = (paint.sourceWidth ?? node.middleBoxGlobal.width) / modifiedScaleX;
  }

  final double height;
  if (paint.fit == Fit.fitHeight) {
    height = node.middleBoxGlobal.height;
  } else if (paint.fit == Fit.fitWidth && paint.hasImageSourceSize) {
    final aspectRatio = paint.sourceWidth! / paint.sourceHeight!;
    height = node.middleBoxGlobal.width / aspectRatio;
  } else {
    height =
        (paint.sourceHeight ?? node.middleBoxGlobal.height) / modifiedScaleY;
  }
  return SizeC(width, height);
}