From b12bc5c4d5c2d18ef45c75c00f46364a6728f3c3 Mon Sep 17 00:00:00 2001
From: bubnikv <bubnikv@gmail.com>
Date: Tue, 10 Dec 2019 11:12:17 +0100
Subject: [PATCH] Optimization in GLCanvas3D::reload_scene(): Use sorting and
 binary search instead of linear search. O(n log n) versus O(n^2)

---
 src/slic3r/GUI/3DScene.hpp    |  2 ++
 src/slic3r/GUI/GLCanvas3D.cpp | 24 +++++++++---------------
 2 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/src/slic3r/GUI/3DScene.hpp b/src/slic3r/GUI/3DScene.hpp
index 8c5040eee2..5d559c246d 100644
--- a/src/slic3r/GUI/3DScene.hpp
+++ b/src/slic3r/GUI/3DScene.hpp
@@ -303,6 +303,8 @@ public:
         int             instance_id;
 		bool operator==(const CompositeID &rhs) const { return object_id == rhs.object_id && volume_id == rhs.volume_id && instance_id == rhs.instance_id; }
 		bool operator!=(const CompositeID &rhs) const { return ! (*this == rhs); }
+		bool operator< (const CompositeID &rhs) const 
+			{ return object_id < rhs.object_id || (object_id == rhs.object_id && (volume_id < rhs.volume_id || (volume_id == rhs.volume_id && instance_id < rhs.instance_id))); }
     };
     CompositeID         composite_id;
     // Fingerprint of the source geometry. For ModelVolumes, it is the ModelVolume::ID and ModelInstanceID, 
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index dcf45e91da..df5900d08e 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -2063,9 +2063,11 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
 
     struct GLVolumeState {
         GLVolumeState() :
-            volume_idx(-1) {}
+            volume_idx(size_t(-1)) {}
         GLVolumeState(const GLVolume* volume, unsigned int volume_idx) :
             composite_id(volume->composite_id), volume_idx(volume_idx) {}
+        GLVolumeState(const GLVolume::CompositeID &composite_id) :
+            composite_id(composite_id), volume_idx(size_t(-1)) {}
 
         GLVolume::CompositeID       composite_id;
         // Volume index in the old GLVolume vector.
@@ -2191,22 +2193,13 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
         }
     }
     sort_remove_duplicates(instance_ids_selected);
+    auto deleted_volumes_lower = [](const GLVolumeState &v1, const GLVolumeState &v2) { return v1.composite_id < v2.composite_id; };
+    std::sort(deleted_volumes.begin(), deleted_volumes.end(), deleted_volumes_lower);
 
     if (m_reload_delayed)
         return;
 
     bool update_object_list = false;
-
-    auto find_old_volume_id = [&deleted_volumes](const GLVolume::CompositeID& id) -> unsigned int {
-        for (unsigned int i = 0; i < (unsigned int)deleted_volumes.size(); ++i)
-        {
-            const GLVolumeState& v = deleted_volumes[i];
-            if (v.composite_id == id)
-                return v.volume_idx;
-        }
-        return (unsigned int)-1;
-    };
-
     if (m_volumes.volumes != glvolumes_new)
 		update_object_list = true;
     m_volumes.volumes = std::move(glvolumes_new);
@@ -2221,9 +2214,10 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
 				assert(it != model_volume_state.end() && it->geometry_id == key.geometry_id);
                 if (it->new_geometry()) {
                     // New volume.
-                    unsigned int old_id = find_old_volume_id(it->composite_id);
-                    if (old_id != (unsigned int)-1)
-                        map_glvolume_old_to_new[old_id] = m_volumes.volumes.size();
+                    auto it_old_volume = std::lower_bound(deleted_volumes.begin(), deleted_volumes.end(), GLVolumeState(it->composite_id), deleted_volumes_lower);
+                    if (it_old_volume != deleted_volumes.end() && it_old_volume->composite_id == it->composite_id)
+                        // If a volume changed its ObjectID, but it reuses a GLVolume's CompositeID, maintain its selection.
+                        map_glvolume_old_to_new[it_old_volume->volume_idx] = m_volumes.volumes.size();
                     m_volumes.load_object_volume(&model_object, obj_idx, volume_idx, instance_idx, m_color_by, m_initialized);
                     m_volumes.volumes.back()->geometry_id = key.geometry_id;
                     update_object_list = true;