Vc + + programming environment with vs2015, doing the zoom and expansion of planar contour,
Use the clipper cut contour offset in the repository,
General process is as follows:
ClipperOffset co.
Float temp=5.0;
Co. AddPaths (insetTemp jtRound, etClosedPolygon);
Co., the Execute (/insetTemp, temp));
With layers of the for loop, and sometimes pops up abort () error, the timing of the pops up in the loop and the position uncertainty,

Which teacher is familiar with, can give directions, thank you very much