X-Git-Url: https://git.tokkee.org/?a=blobdiff_plain;f=src%2Fline-geometry.cpp;h=d050ec458c266605d4142a65e09e4593080508f5;hb=ceb9b97a62780ab7aef6ec4c03f20d776368a112;hp=d7b5fb2ecd9bc66022916c2d7c8298f6c8c07a0e;hpb=5341d52bd89ffc1587300ac4210afb64661af05d;p=inkscape.git

diff --git a/src/line-geometry.cpp b/src/line-geometry.cpp
index d7b5fb2ec..d050ec458 100644
--- a/src/line-geometry.cpp
+++ b/src/line-geometry.cpp
@@ -13,11 +13,11 @@
 
 #include "line-geometry.h"
 #include "inkscape.h"
+#include "desktop.h"
 #include "desktop-style.h"
 #include "desktop-handles.h"
 #include "display/sp-canvas.h"
 #include "display/sodipodi-ctrl.h"
-//#include "display/curve.cpp"
 
 namespace Box3D {
 
@@ -54,7 +54,9 @@ Line &Line::operator=(Line const &line) {
 
 NR::Maybe<NR::Point> Line::intersect(Line const &line) {
     NR::Coord denom = NR::dot(v_dir, line.normal);
-    g_return_val_if_fail(fabs(denom) > 1e-6, NR::Nothing());
+    NR::Maybe<NR::Point> no_point = NR::Nothing();
+    if (fabs(denom) < 1e-6)
+        return no_point;
 
     NR::Coord lambda = (line.d0 - NR::dot(pt, line.normal)) / denom;
     return pt + lambda * v_dir;
@@ -89,18 +91,13 @@ double Line::lambda (NR::Point const pt)
     return lambda;
 }
 
-inline static double determinant (NR::Point const &a, NR::Point const &b)
-{
-    return (a[NR::X] * b[NR::Y] - a[NR::Y] * b[NR::X]);
-}
-
 /* The coordinates of w with respect to the basis {v1, v2} */
 std::pair<double, double> coordinates (NR::Point const &v1, NR::Point const &v2, NR::Point const &w)
 {
     double det = determinant (v1, v2);;
     if (fabs (det) < epsilon) {
-        g_warning ("Vectors do not form a basis.\n");
-        return std::make_pair (0.0, 0.0);
+        // 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;
@@ -112,12 +109,22 @@ std::pair<double, double> coordinates (NR::Point const &v1, NR::Point const &v2,
 bool lies_in_sector (NR::Point const &v1, NR::Point const &v2, NR::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 (NR::dot (v1, v2) < 0);
+    }
     return (coords.first >= 0 and coords.second >= 0);
 }
 
-static double pos_angle (NR::Point A, NR::Point B)
+bool lies_in_quadrangle (NR::Point const &A, NR::Point const &B, NR::Point const &C, NR::Point const &D, NR::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 (NR::Point v, NR::Point w)
 {
-    return fabs (NR::atan2 (A) - NR::atan2 (B));
+    return fabs (NR::atan2 (v) - NR::atan2 (w));
 }
 
 /*
@@ -171,55 +178,21 @@ side_of_intersection (NR::Point const &A, NR::Point const &B, NR::Point const &C
     }
 }
 
-double cross_ratio (NR::Point const &A, NR::Point const &B, NR::Point const &C, NR::Point const &D)
-{
-    Line line (A, D);
-    double lambda_A = line.lambda (A);
-    double lambda_B = line.lambda (B);
-    double lambda_C = line.lambda (C);
-    double lambda_D = line.lambda (D);
-
-    if (fabs (lambda_D - lambda_A) < epsilon || fabs (lambda_C - lambda_B) < epsilon) {
-        // FIXME: What should we return if the cross ratio can't be computed?
-        return 0;
-        //return NR_HUGE;
-    }
-    return (((lambda_C - lambda_A) / (lambda_D - lambda_A)) * ((lambda_D - lambda_B) / (lambda_C - lambda_B)));
-}
-
-double cross_ratio (VanishingPoint const &V, NR::Point const &B, NR::Point const &C, NR::Point const &D)
+NR::Maybe<NR::Point> Line::intersection_with_viewbox (SPDesktop *desktop)
 {
-    if (V.is_finite()) {
-        return cross_ratio (V.get_pos(), B, C, D);
-    } else {
-        Line line (B, D);
-        double lambda_B = line.lambda (B);
-        double lambda_C = line.lambda (C);
-        double lambda_D = line.lambda (D);
-
-        if (fabs (lambda_C - lambda_B) < epsilon) {
-            // FIXME: What should we return if the cross ratio can't be computed?
-            return 0;
-            //return NR_HUGE;
-        }
-        return (lambda_D - lambda_B) / (lambda_C - lambda_B);
+    NR::Rect vb = desktop->get_display_area();
+    /* remaining viewbox corners */
+    NR::Point ul (vb.min()[NR::X], vb.max()[NR::Y]);
+    NR::Point lr (vb.max()[NR::X], vb.min()[NR::Y]);
+
+    std::pair <NR::Point, NR::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 NR::Nothing();
     }
-}
 
-NR::Point fourth_pt_with_given_cross_ratio (NR::Point const &A, NR::Point const &C, NR::Point const &D, double gamma)
-{
-    Line line (A, D);
-    double lambda_A = line.lambda (A);
-    double lambda_C = line.lambda (C);
-    double lambda_D = line.lambda (D);
-
-    double beta = (lambda_C - lambda_A) / (lambda_D - lambda_A);
-    if (fabs (beta - gamma) < epsilon) {
-        // FIXME: How to handle the case when the point can't be computed?
-        // g_warning ("Cannot compute point with given cross ratio.\n");
-        return NR::Point (0.0, 0.0);
-    }
-    return line.point_from_lambda ((beta * lambda_D - gamma * lambda_C) / (beta - gamma));
+    Line line (e.first, e.second);
+    return this->intersect (line);
 }
 
 void create_canvas_point(NR::Point const &pos, double size, guint32 rgba)