* in xmin,ymin... entries, if you don't press enter, you loose your edit (take change into account on leave focus)
* bug when zoom in too much (exception Protocol.TkError("bad screen distance "        -Infm""))
* sometimes the labels for the first ticks are 0.99999932329 ??
* intersection of x=k functions
* resizing of log and modify (buttons disappear)
