onDrag method

void onDrag(
  1. double dx,
  2. double dy
)

Implementation

void onDrag(double dx, double dy) {
  var newHeight = draggedHeight.value + dy;
  var newWidth = draggedWidth.value + dx;

  draggedHeight.value = getTop(newHeight + draggedTop.value > imageHeight.value ? draggedHeight.value : newHeight > 0 ? newHeight : 0);
  draggedWidth.value = getLeft(newWidth + draggedLeft.value > imageWidth.value ? draggedWidth.value : newWidth > 0 ? newWidth : 0);
}