Esempio n. 1
0
void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
                                               Inkscape::SnapCandidatePoint const &p,
                                               Geom::OptRect const &/*bbox_to_snap*/,
                                               ConstraintLine const &c,
                                               std::vector<SPItem const *> const */*it*/) const

{
    if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(p.getSourceType()) == false) {
        return;
    }

    /* Get the lines that we will try to snap to */
    const LineList lines = _getSnapLines(p.getPoint());

    for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
        if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
            // constraint line
            Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p.getPoint();
            Geom::Line line1(point_on_line, point_on_line + c.getDirection());

            // grid/guide line
            Geom::Point const p1 = i->second; // point at guide/grid line
            Geom::Point const p2 = p1 + Geom::rot90(i->first); // 2nd point at guide/grid line
            Geom::Line line2(p1, p2);

            Geom::OptCrossing inters = Geom::OptCrossing(); // empty by default
            try
            {
                inters = Geom::intersection(line1, line2);
            }
            catch (Geom::InfiniteSolutions e)
            {
                // We're probably dealing with parallel lines, so snapping doesn't make any sense here
                continue; // jump to the next iterator in the for-loop
            }

            if (inters) {
                Geom::Point t = line1.pointAt((*inters).ta);
                const Geom::Coord dist = Geom::L2(t - p.getPoint());
                if (dist < getSnapperTolerance()) {
                    // When doing a constrained snap, we're already at an intersection.
                    // This snappoint is therefore fully constrained, so there's no need
                    // to look for additional intersections; just return the snapped point
                    // and forget about the line
                    _addSnappedPoint(sc, t, dist, p.getSourceType(), p.getSourceNum(), true);
                    // For any line that's within range, we will also look at it's "point on line" p1. For guides
                    // this point coincides with its origin; for grids this is of no use, but we cannot
                    // discern between grids and guides here
                    Geom::Coord const dist_p1 = Geom::L2(p1 - p.getPoint());
                    if (dist_p1 < getSnapperTolerance()) {
                        _addSnappedLinesOrigin(sc, p1, dist_p1, p.getSourceType(), p.getSourceNum(), true);
                        // Only relevant for guides; grids don't have an origin per line
                        // Therefore _addSnappedLinesOrigin() will only be implemented for guides
                    }
                }
            }
        }
    }
}
void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
                                               Inkscape::SnapPreferences::PointType const &t,
                                               Geom::Point const &p,
                                               bool const &/*f*/,
                                               Geom::OptRect const &/*bbox_to_snap*/,
                                               ConstraintLine const &c,
                                               std::vector<SPItem const *> const */*it*/) const

{
    if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(t) == false) {
        return;
    }

    /* Get the lines that we will try to snap to */
    const LineList lines = _getSnapLines(p);

    for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
        if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
            /* Normal to the line we're trying to snap along */
            Geom::Point const n(Geom::rot90(Geom::unit_vector(c.getDirection())));

            Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p;

            /* Constant term of the line we're trying to snap along */
            Geom::Coord const q0 = dot(n, point_on_line);
            /* Constant term of the grid or guide line */
            Geom::Coord const q1 = dot(i->first, i->second);

            /* Try to intersect this line with the target line */
            Geom::Point t_2geom(NR_HUGE, NR_HUGE);
            Geom::IntersectorKind const k = Geom::line_intersection(n, q0, i->first, q1, t_2geom);
            Geom::Point t(t_2geom);

            if (k == Geom::intersects) {
                const Geom::Coord dist = L2(t - p);
                if (dist < getSnapperTolerance()) {
    				// When doing a constrained snap, we're already at an intersection.
                    // This snappoint is therefore fully constrained, so there's no need
                    // to look for additional intersections; just return the snapped point
                    // and forget about the line
                    sc.points.push_back(SnappedPoint(t, Inkscape::SNAPTARGET_UNDEFINED, dist, getSnapperTolerance(), getSnapperAlwaysSnap(), true));
                    // The type of the snap target is yet undefined, as we cannot tell whether
                    // we're snapping to grid or the guide lines; must be set by on a higher level
                }
            }
        }
    }
}