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 "inkscape.h"
17 #include "desktop.h"
18 #include "display/canvas-grid.h"
20 /**
21 * \return x rounded to the nearest multiple of c1 plus c0.
22 *
23 * \note
24 * If c1==0 (and c0 is finite), then returns +/-inf. This makes grid spacing of zero
25 * mean "ignore the grid in this dimention". We're currently discussing "good" semantics
26 * for guide/grid snapping.
27 */
29 /* FIXME: move this somewhere else, perhaps */
30 static double round_to_nearest_multiple_plus(double x, double const c1, double const c0)
31 {
32 return floor((x - c0) / c1 + .5) * c1 + c0;
33 }
35 Inkscape::GridSnapper::GridSnapper(SPNamedView const *nv, NR::Coord const d) : LineSnapper(nv, d)
36 {
38 }
40 Inkscape::LineSnapper::LineList Inkscape::GridSnapper::_getSnapLines(NR::Point const &p) const
41 {
42 LineList s;
44 if ( NULL == _named_view ) {
45 return s;
46 }
48 SPCGrid *griditem = NULL;
49 for (GSList *l = _named_view->gridviews; l != NULL; l = l->next) {
50 // FIXME : this is a hack since there is only one view for now
51 // but when we'll handle multiple views, snapping should
52 // must be rethought and maybe only the current view
53 // should give back it's SHOWN lines to snap to
54 // For now, the last SPCGrid in _named_view->gridviews will be used.
55 griditem = SP_CGRID(l->data);
56 }
58 g_assert(griditem != NULL);
60 for (unsigned int i = 0; i < 2; ++i) {
62 /* This is to make sure we snap to only visible grid lines */
63 double scaled_spacing = griditem->sw[i]; // this is spacing of visible lines if screen pixels
65 // convert screen pixels to px
66 // FIXME: after we switch to snapping dist in screen pixels, this will be unnecessary
67 if (SP_ACTIVE_DESKTOP) {
68 scaled_spacing /= SP_ACTIVE_DESKTOP->current_zoom();
69 }
71 NR::Coord const rounded = round_to_nearest_multiple_plus(p[i],
72 scaled_spacing,
73 _named_view->gridorigin[i]);
75 s.push_back(std::make_pair(NR::Dim2(i), rounded));
76 }
78 return s;
79 }
81 /*
82 Local Variables:
83 mode:c++
84 c-file-style:"stroustrup"
85 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
86 indent-tabs-mode:nil
87 fill-column:99
88 End:
89 */
90 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :