From: Magnus Jacobsson <Magnus.Jacobsson@berotec.se>
Date: Thu, 6 Oct 2022 10:36:48 +0000 (+0200)
Subject: arrows: arrow_length_tee: take edge penwidth into account when calculating length
X-Git-Tag: 7.0.1~3^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5ed480a52ddbf89ad5697376d93b95635eb38230;p=graphviz

arrows: arrow_length_tee: take edge penwidth into account when calculating length

The test_edge_node_overlap_tee_edge_arrow test case now succeeds, so
the expectancy that it should fail is removed.

Towards https://gitlab.com/graphviz/graphviz/-/issues/372.
---

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc55cfb99..8dc98dd73 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,7 +21,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Failure of arrowhead and arrowtail to respect penwidth #372 \
-  Fixed also for the `diamond` [edge arrow shape](https://graphviz.org/doc/info/arrows.html#primitive-shapes).
+  Fixed also for the `diamond` and `tee`
+  [edge arrow shapes](https://graphviz.org/doc/info/arrows.html#primitive-shapes).
 - The CMake build system no longer uses the final install location as the
   staging area for example graphs and templates during `cpack`. This bug was
   introduced in Graphviz 4.0.0. #2232
diff --git a/lib/common/arrows.c b/lib/common/arrows.c
index d6bf26a1e..7811d29f1 100644
--- a/lib/common/arrows.c
+++ b/lib/common/arrows.c
@@ -126,6 +126,7 @@ static pointf arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize,
 
 static double arrow_length_generic(double lenfact, double arrowsize, double penwidth, int flag);
 static double arrow_length_normal(double lenfact, double arrowsize, double penwidth, int flag);
+static double arrow_length_tee(double lenfact, double arrowsize, double penwidth, int flag);
 static double arrow_length_box(double lenfact, double arrowsize, double penwidth, int flag);
 static double arrow_length_diamond(double lenfact, double arrowsize, double penwidth, int flag);
 static double arrow_length_dot(double lenfact, double arrowsize, double penwidth, int flag);
@@ -133,7 +134,7 @@ static double arrow_length_dot(double lenfact, double arrowsize, double penwidth
 static const arrowtype_t Arrowtypes[] = {
     {ARR_TYPE_NORM, 1.0, arrow_type_normal, arrow_length_normal},
     {ARR_TYPE_CROW, 1.0, arrow_type_crow, arrow_length_generic},
-    {ARR_TYPE_TEE, 0.5, arrow_type_tee, arrow_length_generic},
+    {ARR_TYPE_TEE, 0.5, arrow_type_tee, arrow_length_tee},
     {ARR_TYPE_BOX, 1.0, arrow_type_box, arrow_length_box},
     {ARR_TYPE_DIAMOND, 1.2, arrow_type_diamond, arrow_length_diamond},
     {ARR_TYPE_DOT, 0.8, arrow_type_dot, arrow_length_dot},
@@ -1054,6 +1055,33 @@ static double arrow_length_normal(double lenfact, double arrowsize,
   return full_length - overlap;
 }
 
+static double arrow_length_tee(double lenfact, double arrowsize,
+			       double penwidth, int flag) {
+    (void)flag;
+
+    // The `tee` arrow shape normally begins and ends with a polyline which
+    // doesn't extend visually beyond its starting point, so we only have to
+    // take penwidth into account if the polygon part visually extends the
+    // polyline part at the start or end points.
+
+    const double nominal_length = lenfact * arrowsize * ARROW_LENGTH;
+    double length = nominal_length;
+
+    // see the 'arrow_type_tee' function for the magical constants used below
+
+    const double polygon_extend_over_polyline_at_start = penwidth / 2 - (1 - 0.6) * nominal_length;
+    if (polygon_extend_over_polyline_at_start > 0) {
+	length += polygon_extend_over_polyline_at_start;
+    }
+
+    const double polygon_extend_over_polyline_at_end = penwidth / 2 - 0.2 * nominal_length;
+    if (polygon_extend_over_polyline_at_start > 0) {
+	length += polygon_extend_over_polyline_at_end;
+    }
+
+    return length;
+}
+
 static double arrow_length_box(double lenfact, double arrowsize,
 			       double penwidth, int flag) {
   (void)flag;
diff --git a/tests/test_edge_node_overlap_tee_edge_arrow.cpp b/tests/test_edge_node_overlap_tee_edge_arrow.cpp
index 383ca97c7..6bc6f074d 100644
--- a/tests/test_edge_node_overlap_tee_edge_arrow.cpp
+++ b/tests/test_edge_node_overlap_tee_edge_arrow.cpp
@@ -6,8 +6,8 @@
 #include "test_utilities.h"
 
 TEST_CASE("Edge node overlap for 'tee' arrow",
-          "[!shouldfail] An edge connected to a node shall touch that node and "
-          "not overlap it too much") {
+          "An edge connected to a node shall touch that node and not overlap "
+          "it too much") {
 
   const std::string_view primitive_arrow_shape = "tee";