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-rw-r--r--src/line-geometry.cpp222
1 files changed, 222 insertions, 0 deletions
diff --git a/src/line-geometry.cpp b/src/line-geometry.cpp
new file mode 100644
index 0000000..1951bd5
--- /dev/null
+++ b/src/line-geometry.cpp
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Routines for dealing with lines (intersections, etc.)
+ *
+ * Authors:
+ * Maximilian Albert <Anhalter42@gmx.de>
+ *
+ * Copyright (C) 2007 authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "line-geometry.h"
+#include "desktop.h"
+#include "desktop-style.h"
+
+#include "display/sp-canvas.h"
+#include "display/sp-ctrlline.h"
+#include "display/sodipodi-ctrl.h"
+#include "ui/control-manager.h"
+
+using Inkscape::ControlManager;
+
+namespace Box3D {
+
+/**
+ * Draw a line beginning at 'start'. If is_endpoint is true, use 'vec' as the endpoint
+ * of the segment. Otherwise interpret it as the direction of the line.
+ * FIXME: Think of a better way to distinguish between the two constructors of lines.
+ */
+Line::Line(Geom::Point const &start, Geom::Point const &vec, bool is_endpoint):
+ pt(start)
+{
+ if (is_endpoint)
+ v_dir = vec - start;
+ else
+ v_dir = vec;
+ normal = v_dir.ccw();
+ d0 = Geom::dot(normal, pt);
+}
+
+Line::Line(Line const &line)
+= default;
+
+Line &Line::operator=(Line const &line) = default;
+
+boost::optional<Geom::Point> Line::intersect(Line const &line) {
+ Geom::Coord denom = Geom::dot(v_dir, line.normal);
+ boost::optional<Geom::Point> no_point;
+ if (fabs(denom) < 1e-6)
+ return no_point;
+
+ Geom::Coord lambda = (line.d0 - Geom::dot(pt, line.normal)) / denom;
+ return pt + lambda * v_dir;
+}
+
+void Line::set_direction(Geom::Point const &dir)
+{
+ v_dir = dir;
+ normal = v_dir.ccw();
+ d0 = Geom::dot(normal, pt);
+}
+
+Geom::Point Line::closest_to(Geom::Point const &pt)
+{
+ /* return the intersection of this line with a perpendicular line passing through pt */
+ boost::optional<Geom::Point> result = this->intersect(Line(pt, (this->v_dir).ccw(), false));
+ g_return_val_if_fail (result, Geom::Point (0.0, 0.0));
+ return *result;
+}
+
+double Line::lambda (Geom::Point const pt)
+{
+ double sign = (Geom::dot (pt - this->pt, this->v_dir) > 0) ? 1.0 : -1.0;
+ double lambda = sign * Geom::L2 (pt - this->pt);
+ // FIXME: It may speed things up (but how much?) if we assume that
+ // pt lies on the line and thus skip the following test
+ Geom::Point test = point_from_lambda (lambda);
+ if (!pts_coincide (pt, test)) {
+ g_warning ("Point does not lie on line.\n");
+ return 0;
+ }
+ return lambda;
+}
+
+/* The coordinates of w with respect to the basis {v1, v2} */
+std::pair<double, double> coordinates (Geom::Point const &v1, Geom::Point const &v2, Geom::Point const &w)
+{
+ double det = determinant (v1, v2);;
+ if (fabs (det) < epsilon) {
+ // vectors are not linearly independent; we indicate this in the return value(s)
+ return std::make_pair (HUGE_VAL, HUGE_VAL);
+ }
+
+ double lambda1 = determinant (w, v2) / det;
+ double lambda2 = determinant (v1, w) / det;
+ return std::make_pair (lambda1, lambda2);
+}
+
+/* whether w lies inside the sector spanned by v1 and v2 */
+bool lies_in_sector (Geom::Point const &v1, Geom::Point const &v2, Geom::Point const &w)
+{
+ std::pair<double, double> coords = coordinates (v1, v2, w);
+ if (coords.first == HUGE_VAL) {
+ // catch the case that the vectors are not linearly independent
+ // FIXME: Can we assume that it's safe to return true if the vectors point in different directions?
+ return (Geom::dot (v1, v2) < 0);
+ }
+ return (coords.first >= 0 && coords.second >= 0);
+}
+
+bool lies_in_quadrangle (Geom::Point const &A, Geom::Point const &B, Geom::Point const &C, Geom::Point const &D, Geom::Point const &pt)
+{
+ return (lies_in_sector (D - A, B - A, pt - A) && lies_in_sector (D - C, B - C, pt - C));
+}
+
+static double pos_angle (Geom::Point v, Geom::Point w)
+{
+ return fabs (Geom::atan2 (v) - Geom::atan2 (w));
+}
+
+/*
+ * Returns the two corners of the quadrangle A, B, C, D spanning the edge that is hit by a semiline
+ * starting at pt and going into direction dir.
+ * If none of the sides is hit, it returns a pair containing two identical points.
+ */
+std::pair<Geom::Point, Geom::Point>
+side_of_intersection (Geom::Point const &A, Geom::Point const &B, Geom::Point const &C, Geom::Point const &D,
+ Geom::Point const &pt, Geom::Point const &dir)
+{
+ Geom::Point dir_A (A - pt);
+ Geom::Point dir_B (B - pt);
+ Geom::Point dir_C (C - pt);
+ Geom::Point dir_D (D - pt);
+
+ std::pair<Geom::Point, Geom::Point> result;
+ double angle = -1;
+ double tmp_angle;
+
+ if (lies_in_sector (dir_A, dir_B, dir)) {
+ result = std::make_pair (A, B);
+ angle = pos_angle (dir_A, dir_B);
+ }
+ if (lies_in_sector (dir_B, dir_C, dir)) {
+ tmp_angle = pos_angle (dir_B, dir_C);
+ if (tmp_angle > angle) {
+ angle = tmp_angle;
+ result = std::make_pair (B, C);
+ }
+ }
+ if (lies_in_sector (dir_C, dir_D, dir)) {
+ tmp_angle = pos_angle (dir_C, dir_D);
+ if (tmp_angle > angle) {
+ angle = tmp_angle;
+ result = std::make_pair (C, D);
+ }
+ }
+ if (lies_in_sector (dir_D, dir_A, dir)) {
+ tmp_angle = pos_angle (dir_D, dir_A);
+ if (tmp_angle > angle) {
+ angle = tmp_angle;
+ result = std::make_pair (D, A);
+ }
+ }
+ if (angle == -1) {
+ // no intersection found; return a pair containing two identical points
+ return std::make_pair (A, A);
+ } else {
+ return result;
+ }
+}
+
+boost::optional<Geom::Point> Line::intersection_with_viewbox (SPDesktop *desktop)
+{
+ Geom::Rect vb = desktop->get_display_area();
+ /* remaining viewbox corners */
+ Geom::Point ul (vb.min()[Geom::X], vb.max()[Geom::Y]);
+ Geom::Point lr (vb.max()[Geom::X], vb.min()[Geom::Y]);
+
+ std::pair <Geom::Point, Geom::Point> e = side_of_intersection (vb.min(), lr, vb.max(), ul, this->pt, this->v_dir);
+ if (e.first == e.second) {
+ // perspective line lies outside the canvas
+ return boost::optional<Geom::Point>();
+ }
+
+ Line line (e.first, e.second);
+ return this->intersect (line);
+}
+
+void create_canvas_point(Geom::Point const &pos, unsigned int size, guint32 rgba)
+{
+ SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+ SPCanvasItem * canvas_pt = sp_canvas_item_new(desktop->getControls(), SP_TYPE_CTRL,
+ "size", size,
+ "filled", 1,
+ "fill_color", rgba,
+ "stroked", 1,
+ "stroke_color", 0x000000ff,
+ NULL);
+ SP_CTRL(canvas_pt)->moveto(pos);
+}
+
+void create_canvas_line(Geom::Point const &p1, Geom::Point const &p2, guint32 rgba)
+{
+ SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+ SPCtrlLine *line = ControlManager::getManager().createControlLine(desktop->getControls(), p1, p2);
+ line->setRgba32(rgba);
+ sp_canvas_item_show(line);
+}
+
+} // namespace Box3D
+
+/*
+ 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 :