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void sp_item_notify_moveto ( SPItem item,
SPGuide const &  mv_g,
int const  snappoint_ix,
double const  position,
bool const  commit 
)

Called by sp_guide_moveto to indicate that the guide line corresponding to g has been moved, and that consequently this item should move with it.

Precondition:
exist [cn in item.constraints] g eq cn.g.
Todo:
effic: skip if mv_g is already satisfied.
Todo:
Reget snappoints, check satisfied.
Todo:
Consider maintaining a set of dirty items.

Definition at line 18 of file sp-item-notify-moveto.cpp.

References Geom::Piecewise< T >::dot(), sp_item_i2d_affine(), and sp_item_write_transform().

{
    g_return_if_fail(SP_IS_ITEM(&item));
    g_return_if_fail( unsigned(snappoint_ix) < 8 );
    Geom::Point const dir( mv_g.normal_to_line );
    double const dir_lensq(dot(dir, dir));
    g_return_if_fail( dir_lensq != 0 );

    std::vector<Inkscape::SnapCandidatePoint> snappoints;
    sp_item_snappoints(&item, snappoints, NULL);
    g_return_if_fail( snappoint_ix < int(snappoints.size()) );

    double const pos0 = dot(dir, snappoints[snappoint_ix].getPoint());
    /// \todo effic: skip if mv_g is already satisfied.

    /* Translate along dir to make dot(dir, snappoints(item)[snappoint_ix]) == position. */

    /* Calculation:
       dot(dir, snappoints[snappoint_ix] + s * dir) = position.
       dot(dir, snappoints[snappoint_ix]) + dot(dir, s * dir) = position.
       pos0 + s * dot(dir, dir) = position.
       s * lensq(dir) = position - pos0.
       s = (position - pos0) / dot(dir, dir). */
    Geom::Translate const tr( ( position - pos0 )
                            * ( dir / dir_lensq ) );
    sp_item_set_i2d_affine(&item, sp_item_i2d_affine(&item) * tr);
    /// \todo Reget snappoints, check satisfied.

    if (commit) {
        /// \todo Consider maintaining a set of dirty items.

        /* Commit repr. */
        {
            sp_item_write_transform(&item, SP_OBJECT_REPR(&item), item.transform);
        }

        sp_item_rm_unsatisfied_cns(item);
#if 0 /* nyi */
        move_cn_to_front(mv_g, snappoint_ix, item.constraints);
        /** \note If the guideline is connected to multiple snappoints of
         * this item, then keeping those cns in order requires that the
         * guide send notifications in order of increasing importance.
         */
#endif
    }
}

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