- Rewrite in libigl style
- zoom with pan rather than scaling
- don't zoom on horizontal scale
- trackball mouseup captured by tweakbar
+ remove global `using namespace std`
+ remove `#define IGL_HEADER_ONLY`
+ guard `#undef max`
+ fix all -Wsign-compare
+ missing `#include <iostream>`
+ missing `#include <fstream>`
+ fix all -Wunused-but-set-variable
+ makefile for libiglviewer.a