This paper proposes new techniques for researchers and developers of drawing systems, especially software for learning and teaching geometry. The techniques allow them to draw geometric figures precisely by using geometric constraints, and to change constrained figures directly. Complicated figures can be easily manipulated by using an interactive, direct, and highly-graphical approach that is realized by a combination of control points and constraint buttons and by graphical tools such as a constrained marker, an electronic protractor, and an electronic divider. The techniques had been implemented as graphical user-interfaces of a micro-world for learning geometry (named GeoBlock). We observed how GeoBlock was used in classrooms and were convinced that students and teachers in junior and senior high schools could draw constrained figures easily by using it.