refactor: zoom relative to viewport center
refactor: zoom relative to viewport center

aterai/java-swing-tips,aterai/java-swing-tips,aoguren/java-swing-tips,aoguren/java-swing-tips,aterai/java-swing-tips,mhcrnl/java-swing-tips,aterai/java-swing-tips,mhcrnl/java-swing-tips,mhcrnl/java-swing-tips,aoguren/java-swing-tips