-extern void chart_init(Bitmap *bm, vcoord_t xmin, vcoord_t ymin, vcoord_t xmax, vcoord_t ymax);
-extern void chart_drawAxis(Bitmap *bm);
-extern void chart_drawCurve(Bitmap *bm, const chart_y_t *curve_y, int curve_cnt);
-extern void chart_drawDots(Bitmap *bm, const chart_x_t *dots_x, const chart_y_t *dots_y, int cnt);
+void chart_init(Bitmap *bm, coord_t xmin, coord_t ymin, coord_t xmax, coord_t ymax);
+void chart_setScale(Bitmap *bm, chart_x_t xmin, chart_y_t ymin, chart_x_t xmax, chart_y_t ymax);
+void chart_drawAxis(Bitmap *bm);
+void chart_drawCurve(Bitmap *bm, const chart_y_t *curve_y, int curve_cnt);
+void chart_drawDots(Bitmap *bm, const chart_x_t *dots_x, const chart_y_t *dots_y, int cnt);