From 47288e9a4c9339ff53db88b3f7819895eeec140c Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Tue, 11 Oct 2016 10:38:21 +0000
Subject: [PATCH] Stitch outlines before display to preserve phase of
 stippling.

Before this commit, the outlines are generated in an arbitrary order
from the kd-tree. This worked just fine for continuous lines, but
for stippling, especially on curves, this meant that most of
the piecewise linear edges would have the stippling phase restart
from zero, leading to a very poor appearance.
---
 src/groupmesh.cpp | 10 +++++++--
 src/polygon.h     |  5 +++++
 src/polyline.cpp  | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/src/groupmesh.cpp b/src/groupmesh.cpp
index afd76bb..dac5869 100644
--- a/src/groupmesh.cpp
+++ b/src/groupmesh.cpp
@@ -401,12 +401,18 @@ void Group::GenerateDisplayItems() {
             displayOutlines.Clear();
 
             if(SS.GW.showEdges || SS.GW.showOutlines) {
+                SOutlineList rawOutlines = {};
                 if(runningMesh.l.n > 0) {
                     // Triangle mesh only; no shell or emphasized edges.
-                    runningMesh.MakeOutlinesInto(&displayOutlines, EdgeKind::EMPHASIZED);
+                    runningMesh.MakeOutlinesInto(&rawOutlines, EdgeKind::EMPHASIZED);
                 } else {
-                    displayMesh.MakeOutlinesInto(&displayOutlines, EdgeKind::SHARP);
+                    displayMesh.MakeOutlinesInto(&rawOutlines, EdgeKind::SHARP);
                 }
+
+                PolylineBuilder builder;
+                builder.MakeFromOutlines(rawOutlines);
+                builder.GenerateOutlines(&displayOutlines);
+                rawOutlines.Clear();
             }
         }
 
diff --git a/src/polygon.h b/src/polygon.h
index 2ef818c..8136860 100644
--- a/src/polygon.h
+++ b/src/polygon.h
@@ -396,6 +396,11 @@ public:
         std::function<void(Vertex *next, Edge *edge)> nextFunc,
         std::function<void(Edge *)> aloneFunc,
         std::function<void()> endFunc = [](){});
+
+    void MakeFromEdges(const SEdgeList &sel);
+    void MakeFromOutlines(const SOutlineList &sol);
+    void GenerateEdges(SEdgeList *sel);
+    void GenerateOutlines(SOutlineList *sol);
 };
 
 #endif
diff --git a/src/polyline.cpp b/src/polyline.cpp
index f7dcace..bddf1ab 100644
--- a/src/polyline.cpp
+++ b/src/polyline.cpp
@@ -187,3 +187,58 @@ void PolylineBuilder::Generate(
         aloneFunc(e);
     }
 }
+
+void PolylineBuilder::MakeFromEdges(const SEdgeList &sel) {
+    for(const SEdge &se : sel.l) {
+        AddEdge(se.a, se.b, (uint32_t)se.auxA, reinterpret_cast<uintptr_t>(&se));
+    }
+}
+
+void PolylineBuilder::MakeFromOutlines(const SOutlineList &ol) {
+    for(const SOutline &so : ol.l) {
+        // Use outline tag as kind, so that emphasized and contour outlines
+        // would not be composed together.
+        AddEdge(so.a, so.b, (uint32_t)so.tag, reinterpret_cast<uintptr_t>(&so));
+    }
+}
+
+void PolylineBuilder::GenerateEdges(SEdgeList *sel) {
+    Vector prev;
+    auto startFunc = [&](Vertex *start, Vertex *next, Edge *e) {
+        sel->AddEdge(start->pos, next->pos, e->kind);
+        prev = next->pos;
+    };
+
+    auto nextFunc = [&](Vertex *next, Edge *e) {
+        sel->AddEdge(prev, next->pos, e->kind);
+        prev = next->pos;
+    };
+
+    auto aloneFunc = [&](Edge *e) {
+        sel->AddEdge(e->a->pos, e->b->pos, e->kind);
+    };
+
+    Generate(startFunc, nextFunc, aloneFunc);
+}
+
+void PolylineBuilder::GenerateOutlines(SOutlineList *sol) {
+    Vector prev;
+    auto startFunc = [&](Vertex *start, Vertex *next, Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(start->pos, next->pos, so->nl, so->nr, so->tag);
+        prev = next->pos;
+    };
+
+    auto nextFunc = [&](Vertex *next, Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(prev, next->pos, so->nl, so->nr, so->tag);
+        prev = next->pos;
+    };
+
+    auto aloneFunc = [&](Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(so->a, so->b, so->nl, so->nr, so->tag);
+    };
+
+    Generate(startFunc, nextFunc, aloneFunc);
+}