1 /**
2 * \file grid-snapper.cpp
3 * \brief Snapping things to grids.
4 *
5 * Authors:
6 * Lauris Kaplinski <lauris@kaplinski.com>
7 * Frank Felfe <innerspace@iname.com>
8 * Carl Hetherington <inkscape@carlh.net>
9 *
10 * Copyright (C) 1999-2002 Authors
11 *
12 * Released under GNU GPL, read the file 'COPYING' for more information
13 */
15 #include "sp-namedview.h"
16 #include "display/canvas-grid.h"
18 /**
19 * \return x rounded to the nearest multiple of c1 plus c0.
20 *
21 * \note
22 * If c1==0 (and c0 is finite), then returns +/-inf. This makes grid spacing of zero
23 * mean "ignore the grid in this dimention". We're currently discussing "good" semantics
24 * for guide/grid snapping.
25 */
27 /* FIXME: move this somewhere else, perhaps */
28 static double round_to_nearest_multiple_plus(double x, double const c1, double const c0)
29 {
30 return floor((x - c0) / c1 + .5) * c1 + c0;
31 }
33 Inkscape::GridSnapper::GridSnapper(SPNamedView const *nv, NR::Coord const d) : LineSnapper(nv, d)
34 {
36 }
38 Inkscape::LineSnapper::LineList Inkscape::GridSnapper::_getSnapLines(NR::Point const &p) const
39 {
40 LineList s;
42 if ( NULL == _named_view ) {
43 return s;
44 }
46 SPCGrid *griditem = NULL;
47 for (GSList *l = _named_view->gridviews; l != NULL; l = l->next) {
48 // FIXME : this is a hack since there is only one view for now
49 // but when we'll handle multiple views, snapping should
50 // must be rethought and maybe only the current view
51 // should give back it's SHOWN lines to snap to
52 // For now, the last SPCGrid in _named_view->gridviews will be used.
53 griditem = SP_CGRID(l->data);
54 }
56 g_assert(griditem != NULL);
58 for (unsigned int i = 0; i < 2; ++i) {
60 /* This is to make sure we snap to only visible grid lines */
61 double const scale = griditem->scaled[i] ? griditem->empspacing : 1;
63 NR::Coord const rounded = round_to_nearest_multiple_plus(p[i],
64 _named_view->gridspacing[i] * scale,
65 _named_view->gridorigin[i]);
67 s.push_back(std::make_pair(NR::Dim2(i), rounded));
68 }
70 return s;
71 }
73 /*
74 Local Variables:
75 mode:c++
76 c-file-style:"stroustrup"
77 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
78 indent-tabs-mode:nil
79 fill-column:99
80 End:
81 */
82 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :