Add scrolling limit to prevent problem as reported in #381
Add scrolling limit to prevent problem as reported in #381

ejeschke/ginga,naojsoft/ginga,stscieisenhamer/ginga,stscieisenhamer/ginga,pllim/ginga,ejeschke/ginga,pllim/ginga,naojsoft/ginga,stscieisenhamer/ginga,naojsoft/ginga,pllim/ginga,ejeschke/ginga