- Reuse the old window in the SDL backend since in some instances switching windows causes issues (OS X fullscreen for instance (while using the SDL backend of course)).
- Clear the SDL render before copying in the framebuffer to remove HOM-like effect.
This helps the crash catcher when there are numerous wad files, for which it's possible that either the wad list, the map or the position is truncated. A more reliable alternative to this should be allocating the char buffer, but I never heard about a way to do this reliably during signal handling.
