From 10059e64318f0c5bac24c55ed230b1e859693fd9 Mon Sep 17 00:00:00 2001
From: Kim Kulling <kim.kulling@googlemail.com>
Date: Mon, 19 Jun 2023 23:21:35 +0200
Subject: [PATCH] Add handling for negative indices.

---
 code/AssetLib/DXF/DXFLoader.cpp | 49 ++++++++++++++-------------------
 code/AssetLib/DXF/DXFLoader.h   |  4 +--
 2 files changed, 22 insertions(+), 31 deletions(-)

diff --git a/code/AssetLib/DXF/DXFLoader.cpp b/code/AssetLib/DXF/DXFLoader.cpp
index 1fb9490cc..a458d0fd8 100644
--- a/code/AssetLib/DXF/DXFLoader.cpp
+++ b/code/AssetLib/DXF/DXFLoader.cpp
@@ -71,7 +71,7 @@ static const aiColor4D AI_DXF_DEFAULT_COLOR(aiColor4D(0.6f, 0.6f, 0.6f, 0.6f));
 // color indices for DXF - 16 are supported, the table is
 // taken directly from the DXF spec.
 static aiColor4D g_aclrDxfIndexColors[] = {
-    aiColor4D (0.6f, 0.6f, 0.6f, 1.0f),
+    aiColor4D(0.6f, 0.6f, 0.6f, 1.0f),
     aiColor4D (1.0f, 0.0f, 0.0f, 1.0f), // red
     aiColor4D (0.0f, 1.0f, 0.0f, 1.0f), // green
     aiColor4D (0.0f, 0.0f, 1.0f, 1.0f), // blue
@@ -88,6 +88,7 @@ static aiColor4D g_aclrDxfIndexColors[] = {
     aiColor4D (1.0f, 1.0f, 1.0f, 1.0f), // white
     aiColor4D (0.6f, 0.0f, 1.0f, 1.0f)  // violet
 };
+
 #define AI_DXF_NUM_INDEX_COLORS (sizeof(g_aclrDxfIndexColors)/sizeof(g_aclrDxfIndexColors[0]))
 #define AI_DXF_ENTITIES_MAGIC_BLOCK "$ASSIMP_ENTITIES_MAGIC"
 
@@ -109,14 +110,6 @@ static const aiImporterDesc desc = {
     "dxf"
 };
 
-// ------------------------------------------------------------------------------------------------
-// Constructor to be privately used by Importer
-DXFImporter::DXFImporter() = default;
-
-// ------------------------------------------------------------------------------------------------
-// Destructor, private as well
-DXFImporter::~DXFImporter() = default;
-
 // ------------------------------------------------------------------------------------------------
 // Returns whether the class can handle the format of the given file.
 bool DXFImporter::CanRead( const std::string& filename, IOSystem* pIOHandler, bool /*checkSig*/ ) const {
@@ -229,7 +222,7 @@ void DXFImporter::ConvertMeshes(aiScene* pScene, DXF::FileData& output) {
         ASSIMP_LOG_VERBOSE_DEBUG("DXF: Unexpanded polycount is ", icount, ", vertex count is ", vcount);
     }
 
-    if (! output.blocks.size()  ) {
+    if (output.blocks.empty()) {
         throw DeadlyImportError("DXF: no data blocks loaded");
     }
 
@@ -587,10 +580,10 @@ void DXFImporter::ParseInsertion(DXF::LineReader& reader, DXF::FileData& output)
     }
 }
 
-#define DXF_POLYLINE_FLAG_CLOSED        0x1
-#define DXF_POLYLINE_FLAG_3D_POLYLINE   0x8
-#define DXF_POLYLINE_FLAG_3D_POLYMESH   0x10
-#define DXF_POLYLINE_FLAG_POLYFACEMESH  0x40
+static constexpr unsigned int DXF_POLYLINE_FLAG_CLOSED = 0x1;
+static constexpr unsigned int DXF_POLYLINE_FLAG_3D_POLYLINE = 0x8;
+static constexpr unsigned int DXF_POLYLINE_FLAG_3D_POLYMESH = 0x10;
+static constexpr unsigned int DXF_POLYLINE_FLAG_POLYFACEMESH = 0x40;
 
 // ------------------------------------------------------------------------------------------------
 void DXFImporter::ParsePolyLine(DXF::LineReader& reader, DXF::FileData& output) {
@@ -639,12 +632,6 @@ void DXFImporter::ParsePolyLine(DXF::LineReader& reader, DXF::FileData& output)
         reader++;
     }
 
-    //if (!(line.flags & DXF_POLYLINE_FLAG_POLYFACEMESH))   {
-    //  DefaultLogger::get()->warn((Formatter::format("DXF: polyline not currently supported: "),line.flags));
-    //  output.blocks.back().lines.pop_back();
-    //  return;
-    //}
-
     if (vguess && line.positions.size() != vguess) {
         ASSIMP_LOG_WARN("DXF: unexpected vertex count in polymesh: ",
             line.positions.size(),", expected ", vguess );
@@ -734,12 +721,18 @@ void DXFImporter::ParsePolyLineVertex(DXF::LineReader& reader, DXF::PolyLine& li
         case 71:
         case 72:
         case 73:
-        case 74:
-            if (cnti == 4) {
-                ASSIMP_LOG_WARN("DXF: more than 4 indices per face not supported; ignoring");
-                break;
+        case 74: {
+                if (cnti == 4) {
+                    ASSIMP_LOG_WARN("DXF: more than 4 indices per face not supported; ignoring");
+                    break;
+                }
+                const int index = reader.ValueAsSignedInt();
+                if (index >= 0) {
+                    indices[cnti++] = static_cast<unsigned int>(index);
+                } else {
+                    ASSIMP_LOG_WARN("DXF: Skip invisible face.");
+                }
             }
-            indices[cnti++] = reader.ValueAsUnsignedInt();
             break;
 
         // color
@@ -777,8 +770,7 @@ void DXFImporter::ParsePolyLineVertex(DXF::LineReader& reader, DXF::PolyLine& li
 }
 
 // ------------------------------------------------------------------------------------------------
-void DXFImporter::Parse3DFace(DXF::LineReader& reader, DXF::FileData& output)
-{
+void DXFImporter::Parse3DFace(DXF::LineReader& reader, DXF::FileData& output) {
     // (note) this is also used for for parsing line entities, so we
     // must handle the vertex_count == 2 case as well.
 
@@ -795,8 +787,7 @@ void DXFImporter::Parse3DFace(DXF::LineReader& reader, DXF::FileData& output)
         if (reader.GroupCode() == 0) {
             break;
         }
-        switch (reader.GroupCode())
-        {
+        switch (reader.GroupCode()) {
 
         // 8 specifies the layer
         case 8:
diff --git a/code/AssetLib/DXF/DXFLoader.h b/code/AssetLib/DXF/DXFLoader.h
index b32ae106f..89a0b79c2 100644
--- a/code/AssetLib/DXF/DXFLoader.h
+++ b/code/AssetLib/DXF/DXFLoader.h
@@ -68,8 +68,8 @@ namespace DXF {
  */
 class DXFImporter : public BaseImporter {
 public:
-    DXFImporter();
-    ~DXFImporter() override;
+    DXFImporter() = default;
+    ~DXFImporter() override = default;
 
     // -------------------------------------------------------------------
     /** Returns whether the class can handle the format of the given file.