Simplify some code. Fix rounding of arrow locations. 
Simplify some code. Fix rounding of arrow locations. 
WoLpH/skim,ycaihua/skim-app,WoLpH/skim,ycaihua/skim-app,ycaihua/skim-app,WoLpH/skim,WoLpH/skim,ycaihua/skim-app,WoLpH/skim,ycaihua/skim-app