STEP: Implementation ported from BambuStudio:

CMake handling is different

STEP: Removed preprocessing stage

STEP: Small refactoring

STEP: Bigger refactoring

STEP: Changed naming on loaded object and volumes:
If the STEP contains exactly one named volume, the object and its first
volume will both have that name. Otherwise, filename w/o suffix is used
as object name and volumes are named using names from the STEP (if there
is none, untranslated "PartN" string is used).

STEP: Load the libraries dynamically on Win

wip

13 files changed, 443 insertions, 4 deletions

diff --git a/deps/CMakeLists.txt b/deps/CMakeLists.txt
index 56a8fa429..0fe4e41c7 100644
--- a/deps/CMakeLists.txt
+++ b/deps/CMakeLists.txt
@@ -189,6 +189,7 @@ endif ()
 include(JPEG/JPEG.cmake)
 include(TIFF/TIFF.cmake)
 include(wxWidgets/wxWidgets.cmake)
+include(OCCT/OCCT.cmake)
 
 set(_dep_list
     dep_Boost
@@ -200,6 +201,7 @@ set(_dep_list
     dep_OpenVDB
     dep_OpenCSG
     dep_CGAL
+    dep_OCCT
     ${PNG_PKG}
     ${ZLIB_PKG}
     ${EXPAT_PKG}
diff --git a/deps/OCCT/OCCT.cmake b/deps/OCCT/OCCT.cmake
new file mode 100644
index 000000000..9981ac15e
--- /dev/null
+++ b/deps/OCCT/OCCT.cmake
@@ -0,0 +1,22 @@
+prusaslicer_add_cmake_project(OCCT
+    #LMBBS: changed version to 7.6.2
+    URL https://github.com/Open-Cascade-SAS/OCCT/archive/refs/tags/V7_6_2.zip
+    URL_HASH SHA256=c696b923593e8c18d059709717dbf155b3e72fdd283c8522047a790ec3a432c5
+
+    CMAKE_ARGS
+        -DINSTALL_DIR_LAYOUT=Unix # LMBBS
+        -DBUILD_LIBRARY_TYPE=Static
+        -DUSE_TK=OFF
+        -DUSE_TBB=OFF
+        -DUSE_FREETYPE=OFF
+	    -DUSE_FFMPEG=OFF
+	    -DUSE_VTK=OFF
+	    -DUSE_FREETYPE=OFF
+	    -DBUILD_MODULE_ApplicationFramework=OFF
+        #-DBUILD_MODULE_DataExchange=OFF
+        -DBUILD_MODULE_Draw=OFF
+		-DBUILD_MODULE_FoundationClasses=OFF
+		-DBUILD_MODULE_ModelingAlgorithms=OFF
+		-DBUILD_MODULE_ModelingData=OFF
+		-DBUILD_MODULE_Visualization=OFF
+)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index cfee06342..2ea8eaa04 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -15,11 +15,9 @@ add_subdirectory(semver)
 add_subdirectory(libigl)
 add_subdirectory(hints)
 add_subdirectory(qoi)
-
-# Adding libnest2d project for bin packing...
 add_subdirectory(libnest2d)
-
 add_subdirectory(libslic3r)
+add_subdirectory(occt_wrapper)
 
 if (SLIC3R_GUI)
     add_subdirectory(imgui)
@@ -127,6 +125,7 @@ if (NOT WIN32 AND NOT APPLE)
 endif ()
 
 target_link_libraries(PrusaSlicer libslic3r cereal)
+
 if (APPLE)
 #    add_compile_options(-stdlib=libc++)
 #    add_definitions(-DBOOST_THREAD_DONT_USE_CHRONO -DBOOST_NO_CXX11_RVALUE_REFERENCES -DBOOST_THREAD_USES_MOVE)
diff --git a/src/libslic3r/CMakeLists.txt b/src/libslic3r/CMakeLists.txt
index 41ad68db5..52ea9be08 100644
--- a/src/libslic3r/CMakeLists.txt
+++ b/src/libslic3r/CMakeLists.txt
@@ -94,6 +94,8 @@ add_library(libslic3r STATIC
     Format/STL.hpp
     Format/SL1.hpp
     Format/SL1.cpp
+    Format/STEP.hpp
+    Format/STEP.cpp
     GCode/ThumbnailData.cpp
     GCode/ThumbnailData.hpp
     GCode/Thumbnails.cpp
diff --git a/src/libslic3r/Format/STEP.cpp b/src/libslic3r/Format/STEP.cpp
new file mode 100644
index 000000000..9b4d2c9ea
--- /dev/null
+++ b/src/libslic3r/Format/STEP.cpp
@@ -0,0 +1,110 @@
+#include "STEP.hpp"
+#include "occt_wrapper/OCCTWrapper.hpp"
+
+#include "libslic3r/Model.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+
+#include <string>
+#include <functional>
+
+#ifdef _WIN32
+    #include<windows.h>
+#else
+    #include<occt_wrapper/OCCTWrapper.hpp>
+    #include <dlfcn.h>
+#endif
+
+
+namespace Slic3r {
+
+LoadStepFn get_load_step_fn()
+{
+    static LoadStepFn load_step_fn = nullptr;
+
+    if (!load_step_fn) {
+#ifdef _WIN32
+        HMODULE module = LoadLibraryW(L"OCCTWrapper.dll");
+        if (module == NULL)
+            throw Slic3r::RuntimeError("Cannot load OCCTWrapper.dll");
+
+        try {
+            const char* fn_name = "load_step_internal";
+            FARPROC farproc = GetProcAddress(module, fn_name);
+            if (! farproc) {
+                DWORD ec = GetLastError();
+                throw Slic3r::RuntimeError(std::string("Cannot load function from OCCTWrapper.dll: ") + fn_name
+                                           + "\n\nError code: " + std::to_string(ec));
+            }
+            load_step_fn = reinterpret_cast<LoadStepFn>(farproc);
+        } catch (const Slic3r::RuntimeError&) {
+            FreeLibrary(module);
+            throw;
+        }
+#else
+        void *plugin_ptr = dlopen("OCCTWrapper.so", RTLD_NOW | RTLD_GLOBAL);
+
+        if (plugin_ptr) {
+            load_step_fn = reinterpret_cast<LoadStepFn>(dlsym(plugin_ptr, "load_step_internal"));
+            if (!load_step_fn) {
+                dlclose(plugin_ptr);
+            }
+        }
+#endif
+    }
+
+    return load_step_fn;
+}
+
+bool load_step(const char *path, Model *model /*BBS:, ImportStepProgressFn proFn*/)
+{
+    OCCTResult occt_object;
+
+    LoadStepFn load_step_fn = get_load_step_fn();
+
+    if (!load_step_fn)
+        return false;
+
+    load_step_fn(path, &occt_object);
+
+    assert(! occt_object.volumes.empty());
+    
+    assert(boost::algorithm::iends_with(occt_object.object_name, ".stp")
+        || boost::algorithm::iends_with(occt_object.object_name, ".step"));
+    occt_object.object_name.erase(occt_object.object_name.find("."));
+    assert(! occt_object.object_name.empty());
+
+
+    ModelObject* new_object = model->add_object();
+    new_object->input_file = path;
+    if (new_object->volumes.size() == 1 && ! occt_object.volumes.front().volume_name.empty())
+        new_object->name = new_object->volumes.front()->name;
+    else
+        new_object->name = occt_object.object_name;
+
+
+    for (size_t i=0; i<occt_object.volumes.size(); ++i) {
+        indexed_triangle_set its;
+        for (size_t j=0; j<occt_object.volumes[i].vertices.size(); ++j)
+            its.vertices.emplace_back(Vec3f(occt_object.volumes[i].vertices[j][0],
+                                            occt_object.volumes[i].vertices[j][1],
+                                            occt_object.volumes[i].vertices[j][2]));
+        for (size_t j=0; j<occt_object.volumes[i].indices.size(); ++j)
+            its.indices.emplace_back(Vec3i(occt_object.volumes[i].indices[j][0],
+                                           occt_object.volumes[i].indices[j][1],
+                                           occt_object.volumes[i].indices[j][2]));
+        its_merge_vertices(its, true);
+        TriangleMesh triangle_mesh(std::move(its));
+        ModelVolume* new_volume = new_object->add_volume(std::move(triangle_mesh));
+
+        new_volume->name = occt_object.volumes[i].volume_name.empty()
+                       ? std::string("Part") + std::to_string(i+1)
+                       : occt_object.volumes[i].volume_name;
+        new_volume->source.input_file = path;
+        new_volume->source.object_idx = (int)model->objects.size() - 1;
+        new_volume->source.volume_idx = (int)new_object->volumes.size() - 1;
+    }
+
+    return true;
+}
+
+}; // namespace Slic3r
diff --git a/src/libslic3r/Format/STEP.hpp b/src/libslic3r/Format/STEP.hpp
new file mode 100644
index 000000000..8fbc604d8
--- /dev/null
+++ b/src/libslic3r/Format/STEP.hpp
@@ -0,0 +1,19 @@
+// Original implementation of STEP format import created by Bambulab.
+// https://github.com/bambulab/BambuStudio
+// Forked off commit 1555904, modified by Prusa Research.
+
+#ifndef slic3r_Format_STEP_hpp_
+#define slic3r_Format_STEP_hpp_
+
+namespace Slic3r {
+
+class Model;
+
+//typedef std::function<void(int load_stage, int current, int total, bool& cancel)> ImportStepProgressFn;
+
+// Load a step file into a provided model.
+extern bool load_step(const char *path_str, Model *model /*LMBBS:, ImportStepProgressFn proFn = nullptr*/);
+
+}; // namespace Slic3r
+
+#endif /* slic3r_Format_STEP_hpp_ */
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index efc66f478..77011800d 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -13,6 +13,7 @@
 #include "Format/OBJ.hpp"
 #include "Format/STL.hpp"
 #include "Format/3mf.hpp"
+#include "Format/STEP.hpp"
 
 #include <float.h>
 
@@ -114,6 +115,8 @@ Model Model::read_from_file(const std::string& input_file, DynamicPrintConfig* c
         result = load_stl(input_file.c_str(), &model);
     else if (boost::algorithm::iends_with(input_file, ".obj"))
         result = load_obj(input_file.c_str(), &model);
+    else if (boost::algorithm::iends_with(input_file, ".step") || boost::algorithm::iends_with(input_file, ".stp"))
+        result = load_step(input_file.c_str(), &model);
     else if (boost::algorithm::iends_with(input_file, ".amf") || boost::algorithm::iends_with(input_file, ".amf.xml"))
         result = load_amf(input_file.c_str(), config, config_substitutions, &model, options & LoadAttribute::CheckVersion);
     else if (boost::algorithm::iends_with(input_file, ".3mf"))
diff --git a/src/libslic3r/TriangleMesh.cpp b/src/libslic3r/TriangleMesh.cpp
index 93a09a0d9..807ebcc9a 100644
--- a/src/libslic3r/TriangleMesh.cpp
+++ b/src/libslic3r/TriangleMesh.cpp
@@ -1370,4 +1370,5 @@ bool its_write_stl_binary(const char *file, const char *label, const std::vector
     return true;
 }
 
+
 } // namespace Slic3r
diff --git a/src/occt_wrapper/CMakeLists.txt b/src/occt_wrapper/CMakeLists.txt
new file mode 100644
index 000000000..2629e1d59
--- /dev/null
+++ b/src/occt_wrapper/CMakeLists.txt
@@ -0,0 +1,51 @@
+cmake_minimum_required(VERSION 3.13)
+project(OCCTWrapper)
+
+add_library(OCCTWrapper SHARED OCCTWrapper.cpp)
+
+set_target_properties(OCCTWrapper
+    PROPERTIES
+    LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/src"
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/src"
+    PREFIX ""
+)
+
+include(GenerateExportHeader)
+
+generate_export_header(OCCTWrapper)
+
+find_package(OpenCASCADE 7.6.2 REQUIRED)
+
+set(OCCT_LIBS
+    TKXDESTEP
+    TKSTEP
+    TKSTEP209
+    TKSTEPAttr
+    TKSTEPBase
+    TKXCAF
+    TKXSBase
+    TKVCAF
+    TKCAF
+    TKLCAF
+    TKCDF
+    TKV3d
+    TKService
+    TKMesh
+    TKBO
+    TKPrim
+    TKHLR
+    TKShHealing
+    TKTopAlgo
+    TKGeomAlgo
+    TKBRep
+    TKGeomBase
+    TKG3d
+    TKG2d
+    TKMath
+    TKernel
+)
+
+target_include_directories(OCCTWrapper PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+target_include_directories(OCCTWrapper PUBLIC ${OpenCASCADE_INCLUDE_DIR})
+target_link_libraries(OCCTWrapper ${OCCT_LIBS})
+
diff --git a/src/occt_wrapper/OCCTWrapper.cpp b/src/occt_wrapper/OCCTWrapper.cpp
new file mode 100644
index 000000000..87f15e7f9
--- /dev/null
+++ b/src/occt_wrapper/OCCTWrapper.cpp
@@ -0,0 +1,201 @@
+#include "OCCTWrapper.hpp"
+
+#include "occtwrapper_export.h"
+
+#include <cassert>
+
+#ifdef _WIN32
+#define DIR_SEPARATOR '\\'
+#else
+#define DIR_SEPARATOR '/'
+#endif
+
+#include "STEPCAFControl_Reader.hxx"
+#include "BRepMesh_IncrementalMesh.hxx"
+#include "XCAFDoc_DocumentTool.hxx"
+#include "XCAFDoc_ShapeTool.hxx"
+#include "XCAFApp_Application.hxx"
+#include "TopoDS_Builder.hxx"
+#include "TopoDS.hxx"
+#include "TDataStd_Name.hxx"
+#include "BRepBuilderAPI_Transform.hxx"
+#include "TopExp_Explorer.hxx"
+#include "BRep_Tool.hxx"
+
+const double STEP_TRANS_CHORD_ERROR = 0.005;
+const double STEP_TRANS_ANGLE_RES = 1;
+
+// const int LOAD_STEP_STAGE_READ_FILE          = 0;
+// const int LOAD_STEP_STAGE_GET_SOLID          = 1;
+// const int LOAD_STEP_STAGE_GET_MESH           = 2;
+
+namespace Slic3r {
+
+struct NamedSolid {
+    NamedSolid(const TopoDS_Shape& s,
+               const std::string& n) : solid{s}, name{n} {}
+    const TopoDS_Shape solid;
+    const std::string  name;
+};
+
+static void getNamedSolids(const TopLoc_Location& location, const Handle(XCAFDoc_ShapeTool) shapeTool,
+                           const TDF_Label label, std::vector<NamedSolid>& namedSolids)
+{
+    TDF_Label referredLabel{label};
+    if (shapeTool->IsReference(label))
+        shapeTool->GetReferredShape(label, referredLabel);
+
+    std::string name;
+    Handle(TDataStd_Name) shapeName;
+    if (referredLabel.FindAttribute(TDataStd_Name::GetID(), shapeName))
+        name = TCollection_AsciiString(shapeName->Get()).ToCString();
+
+    TopLoc_Location localLocation = location * shapeTool->GetLocation(label);
+    TDF_LabelSequence components;
+    if (shapeTool->GetComponents(referredLabel, components)) {
+        for (Standard_Integer compIndex = 1; compIndex <= components.Length(); ++compIndex) {
+            getNamedSolids(localLocation, shapeTool, components.Value(compIndex), namedSolids);
+        }
+    } else {
+        TopoDS_Shape shape;
+        shapeTool->GetShape(referredLabel, shape);
+        TopAbs_ShapeEnum shape_type = shape.ShapeType();
+        BRepBuilderAPI_Transform transform(shape, localLocation, Standard_True);
+        switch (shape_type) {
+        case TopAbs_COMPOUND:
+            namedSolids.emplace_back(TopoDS::Compound(transform.Shape()), name);
+            break;
+        case TopAbs_COMPSOLID:
+            namedSolids.emplace_back(TopoDS::CompSolid(transform.Shape()), name);
+            break;
+        case TopAbs_SOLID:
+            namedSolids.emplace_back(TopoDS::Solid(transform.Shape()), name);
+            break;
+        default:
+            break;
+        }
+    }
+}
+
+extern "C" OCCTWRAPPER_EXPORT bool load_step_internal(const char *path, OCCTResult* res /*BBS:, ImportStepProgressFn proFn*/)
+{
+try {
+    bool cb_cancel = false;
+    //if (proFn) {
+    //    proFn(LOAD_STEP_STAGE_READ_FILE, 0, 1, cb_cancel);
+    //    if (cb_cancel)
+    //        return false;
+    //}
+    
+
+    std::vector<NamedSolid> namedSolids;
+    Handle(TDocStd_Document) document;
+    Handle(XCAFApp_Application) application = XCAFApp_Application::GetApplication();
+    application->NewDocument(path, document);
+    STEPCAFControl_Reader reader;
+    reader.SetNameMode(true);
+    //BBS: Todo, read file is slow which cause the progress_bar no update and gui no response
+    IFSelect_ReturnStatus stat = reader.ReadFile(path);
+    if (stat != IFSelect_RetDone || !reader.Transfer(document)) {
+        application->Close(document);
+        res->error_str = std::string{"Could not read '"} + path + "'";
+        return false;
+    }
+    Handle(XCAFDoc_ShapeTool) shapeTool = XCAFDoc_DocumentTool::ShapeTool(document->Main());
+    TDF_LabelSequence topLevelShapes;
+    shapeTool->GetFreeShapes(topLevelShapes);
+
+    Standard_Integer topShapeLength = topLevelShapes.Length() + 1;
+    for (Standard_Integer iLabel = 1; iLabel < topShapeLength; ++iLabel) {
+        //if (proFn) {
+        //    proFn(LOAD_STEP_STAGE_GET_SOLID, iLabel, topShapeLength, cb_cancel);
+        //    if (cb_cancel) {
+        //        shapeTool.reset(nullptr);
+        //        application->Close(document);
+        //        return false;
+        //    }
+        //}
+        getNamedSolids(TopLoc_Location{}, shapeTool, topLevelShapes.Value(iLabel), namedSolids);
+    }
+
+    
+
+    // Now the object name. Set it to filename without suffix.
+    // This will later be changed if only one volume is loaded.
+    const char *last_slash = strrchr(path, DIR_SEPARATOR);
+    std::string obj_name((last_slash == nullptr) ? path : last_slash + 1);
+    res->object_name = obj_name;
+
+    for (size_t i = 0; i < namedSolids.size(); ++i) {
+        //BBS:if (proFn) {
+        //    proFn(LOAD_STEP_STAGE_GET_MESH, i, namedSolids.size(), cb_cancel);
+        //    if (cb_cancel) {
+        //        model->delete_object(new_object);
+        //        shapeTool.reset(nullptr);
+        //        application->Close(document);
+        //        return false;
+        //    }
+        //}
+
+        res->volumes.emplace_back();
+        auto& vertices = res->volumes.back().vertices;
+        auto& indices  = res->volumes.back().indices;
+
+        BRepMesh_IncrementalMesh mesh(namedSolids[i].solid, STEP_TRANS_CHORD_ERROR, false, STEP_TRANS_ANGLE_RES, true);
+
+        for (TopExp_Explorer anExpSF(namedSolids[i].solid, TopAbs_FACE); anExpSF.More(); anExpSF.Next()) {
+            const int aNodeOffset = int(vertices.size());
+            const TopoDS_Shape& aFace = anExpSF.Current();
+            TopLoc_Location aLoc;
+            Handle(Poly_Triangulation) aTriangulation = BRep_Tool::Triangulation(TopoDS::Face(aFace), aLoc);
+            if (aTriangulation.IsNull())
+                continue;
+
+            // First copy vertices (will create duplicates).
+            gp_Trsf aTrsf = aLoc.Transformation();
+            for (Standard_Integer aNodeIter = 1; aNodeIter <= aTriangulation->NbNodes(); ++aNodeIter) {
+                gp_Pnt aPnt = aTriangulation->Node(aNodeIter);
+                aPnt.Transform(aTrsf);
+                vertices.push_back({float(aPnt.X()), float(aPnt.Y()), float(aPnt.Z())});
+            }
+            // Now the indices.
+            const TopAbs_Orientation anOrientation = anExpSF.Current().Orientation();
+            for (Standard_Integer aTriIter = 1; aTriIter <= aTriangulation->NbTriangles(); ++aTriIter) {
+                Poly_Triangle aTri = aTriangulation->Triangle(aTriIter);
+
+                Standard_Integer anId[3];
+                aTri.Get(anId[0], anId[1], anId[2]);
+                if (anOrientation == TopAbs_REVERSED)
+                    std::swap(anId[1], anId[2]);
+
+                // Account for the vertices we already have from previous faces.
+                // anId is 1-based index !
+                indices.push_back({anId[0] - 1 + aNodeOffset,
+                                   anId[1] - 1 + aNodeOffset,
+                                   anId[2] - 1 + aNodeOffset});
+            }
+        }
+
+        res->volumes.back().volume_name = namedSolids[i].name;
+
+        if (vertices.empty())
+            res->volumes.pop_back();        
+    }
+
+    shapeTool.reset(nullptr);
+    application->Close(document);
+
+    if (res->volumes.empty())
+        return false;
+} catch (const std::exception& ex) {
+    res->error_str = ex.what();
+    return false;
+} catch (...) {
+    res->error_str = "An exception was thrown in load_step_internal.";
+    return false;
+}
+    
+    return true;
+}
+
+}; // namespace Slic3r
diff --git a/src/occt_wrapper/OCCTWrapper.hpp b/src/occt_wrapper/OCCTWrapper.hpp
new file mode 100644
index 000000000..e87becb70
--- /dev/null
+++ b/src/occt_wrapper/OCCTWrapper.hpp
@@ -0,0 +1,27 @@
+
+#ifndef occtwrapper_OCCTWrapper_hpp_
+#define occtwrapper_OCCTWrapper_hpp_
+
+#include <array>
+#include <string>
+#include <vector>
+
+namespace Slic3r {
+
+struct OCCTVolume {
+    std::string volume_name;
+    std::vector<std::array<float, 3>> vertices;
+    std::vector<std::array<int, 3>> indices;
+};
+
+struct OCCTResult {
+    std::string error_str;
+    std::string object_name;
+    std::vector<OCCTVolume> volumes;
+};
+
+using LoadStepFn = bool (*)(const char *path, OCCTResult* occt_result);
+
+}; // namespace Slic3r
+
+#endif // occtwrapper_OCCTWrapper_hpp_
diff --git a/src/slic3r/GUI/GUI_App.cpp b/src/slic3r/GUI/GUI_App.cpp
index 5bc770b2c..6362dc609 100644
--- a/src/slic3r/GUI/GUI_App.cpp
+++ b/src/slic3r/GUI/GUI_App.cpp
@@ -482,10 +482,11 @@ struct FileWildcards {
 static const FileWildcards file_wildcards_by_type[FT_SIZE] = {
     /* FT_STL */     { "STL files"sv,       { ".stl"sv } },
     /* FT_OBJ */     { "OBJ files"sv,       { ".obj"sv } },
+    /* FT_STEP */    { "STEP files"sv,      { ".stp"sv, ".step"sv } },
     /* FT_AMF */     { "AMF files"sv,       { ".amf"sv, ".zip.amf"sv, ".xml"sv } },
     /* FT_3MF */     { "3MF files"sv,       { ".3mf"sv } },
     /* FT_GCODE */   { "G-code files"sv,    { ".gcode"sv, ".gco"sv, ".g"sv, ".ngc"sv } },
-    /* FT_MODEL */   { "Known files"sv,     { ".stl"sv, ".obj"sv, ".3mf"sv, ".amf"sv, ".zip.amf"sv, ".xml"sv } },
+    /* FT_MODEL */   { "Known files"sv,     { ".stl"sv, ".obj"sv, ".3mf"sv, ".amf"sv, ".zip.amf"sv, ".xml"sv, ".step"sv, ".stp"sv } },
     /* FT_PROJECT */ { "Project files"sv,   { ".3mf"sv, ".amf"sv, ".zip.amf"sv } },
     /* FT_GALLERY */ { "Known files"sv,     { ".stl"sv, ".obj"sv } },
 
diff --git a/src/slic3r/GUI/GUI_App.hpp b/src/slic3r/GUI/GUI_App.hpp
index c60dc8d6f..8775a5f31 100644
--- a/src/slic3r/GUI/GUI_App.hpp
+++ b/src/slic3r/GUI/GUI_App.hpp
@@ -53,6 +53,7 @@ enum FileType
 {
     FT_STL,
     FT_OBJ,
+    FT_STEP,
     FT_AMF,
     FT_3MF,
     FT_GCODE,