1 files changed, 89 insertions, 0 deletions
diff --git a/src/sp-item-notify-moveto.cpp b/src/sp-item-notify-moveto.cpp
new file mode 100644
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+++ b/src/sp-item-notify-moveto.cpp
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+/** \file
+ * Implementation of sp_item_notify_moveto().
+ */
+
+#include <2geom/transforms.h>
+#include <vector>
+
+#include "sp-item-notify-moveto.h"
+
+#include "object/sp-guide.h"
+#include "object/sp-item.h"
+#include "object/sp-item-rm-unsatisfied-cns.h"
+
+#define return_if_fail(test) if (!(test)) { printf("WARNING: assertion '%s' failed", #test); return; }
+
+/**
+ * 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.
+ *
+ * \pre exist [cn in item.constraints] g eq cn.g.
+ */
+void sp_item_notify_moveto(SPItem &item, SPGuide const &mv_g, int const snappoint_ix,
+                           double const position, bool const commit)
+{
+    return_if_fail(SP_IS_ITEM(&item));
+    return_if_fail( unsigned(snappoint_ix) < 8 );
+    Geom::Point const dir( mv_g.getNormal() );
+    double const dir_lensq(dot(dir, dir));
+    return_if_fail( dir_lensq != 0 );
+
+    std::vector<Inkscape::SnapCandidatePoint> snappoints;
+    item.getSnappoints(snappoints, nullptr);
+    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 ) );
+    item.set_i2d_affine(item.i2dt_affine() * tr);
+    /// \todo Reget snappoints, check satisfied.
+
+    if (commit) {
+        /// \todo Consider maintaining a set of dirty items.
+
+        /* Commit repr. */
+        {
+            item.doWriteTransform(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
+    }
+}
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :