g++  -c -I$QTDIR/include -pipe -O2  -o MyCanvas.o MyCanvas.cc
g++  -c -I$QTDIR/include -pipe -O2  -o Square.o Square.cpp
g++ -L$QTDIR/lib -Wl,-rpath,$QTDIR/lib  -o Square   MyCanvas.o Square.o  -lqt
