limitTransAndScale method

void limitTransAndScale(Matrix4 matrix, Rect content)

limits the maximum scale and X translation of the given matrix

@param matrix

Implementation

void limitTransAndScale(Matrix4 matrix, Rect content) {
  for (int i = 0; i < 16; i++) {
    matrixBuffer[i] = matrix.storage[i];
  }

  double curTransX = matrixBuffer[12]!;
  double curScaleX = matrixBuffer[0]!;

  double curTransY = matrixBuffer[13]!;
  double curScaleY = matrixBuffer[5]!;

  // min scale-x is 1f
  _scaleX = min(max(_minScaleX, curScaleX), _maxScaleX);

  // min scale-y is 1f
  _scaleY = min(max(_minScaleY, curScaleY), _maxScaleY);

  double width = 0;
  double height = 0;

  width = content.width;
  height = content.height;

  double maxTransX = -width * (_scaleX - 1);
  _transX = min(max(curTransX, maxTransX - _transOffsetX!), _transOffsetX!);

  double maxTransY = height * (_scaleY - 1);
  _transY = max(min(curTransY, maxTransY + _transOffsetY!), -_transOffsetY!);

  matrixBuffer[12] = _transX;
  matrixBuffer[0] = _scaleX;

  matrixBuffer[13] = _transY;
  matrixBuffer[5] = _scaleY;

  for (int i = 0; i < 16; i++) {
    matrix.storage[i] = matrixBuffer[i]!;
  }
}