setVerticalMargins method
Sets the vertical scrolling margin to top and bottom.
Both values must be between 0 and viewHeight - 1.
Implementation
void setVerticalMargins(int top, int bottom) {
_marginTop = top.clamp(0, viewHeight - 1);
_marginBottom = bottom.clamp(0, viewHeight - 1);
_marginTop = min(_marginTop, _marginBottom);
_marginBottom = max(_marginTop, _marginBottom);
}