feat(editor): undoing movement/transformations

core/src/common.cpp

@@ -15,24 +15,8 @@ Handles editorToolHandles;
 
 
 std::vector<std::shared_ptr<Instance>> currentSelection;
-std::vector<SelectionUpdateHandler> selectionUpdateListeners;
 std::vector<PropertyUpdateHandler> propertyUpdatelisteners;
 
-void setSelection(std::vector<std::shared_ptr<Instance>> newSelection, bool fromExplorer) {
-    for (SelectionUpdateHandler handler : selectionUpdateListeners) {
-        handler(currentSelection, newSelection, fromExplorer);
-    }
-
-    currentSelection = newSelection;
-}
-
-const std::vector<std::shared_ptr<Instance>> getSelection() {
-    return currentSelection;
-}
-
-void addSelectionListener(SelectionUpdateHandler handler) {
-    selectionUpdateListeners.push_back(handler);
-}
 
 void sendPropertyUpdatedSignal(std::shared_ptr<Instance> instance, std::string property, Variant newValue) {
     for (PropertyUpdateHandler handler : propertyUpdatelisteners) {

core/src/common.h

@@ -1,7 +1,7 @@
 #pragma once
 #include "objects/base/instance.h"
 #include "handles.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include "objects/datamodel.h"
 #include "camera.h"
 #include <functional>
@@ -11,7 +11,6 @@ class Instance;
 // typedef std::function<void(std::shared_ptr<Instance> element, std::optional<std::shared_ptr<Instance>> newParent)> HierarchyUpdateHandler;
 typedef std::function<void(std::shared_ptr<Instance> object, std::optional<std::shared_ptr<Instance>> oldParent, std::optional<std::shared_ptr<Instance>> newParent)> HierarchyPreUpdateHandler;
 typedef std::function<void(std::shared_ptr<Instance> object, std::optional<std::shared_ptr<Instance>> oldParent, std::optional<std::shared_ptr<Instance>> newParent)> HierarchyPostUpdateHandler;
-typedef std::function<void(std::vector<std::shared_ptr<Instance>> oldSelection, std::vector<std::shared_ptr<Instance>> newSelection, bool fromExplorer)> SelectionUpdateHandler;
 typedef std::function<void(std::shared_ptr<Instance> instance, std::string property, Variant newValue)> PropertyUpdateHandler;
 
 // TEMPORARY COMMON DATA FOR VARIOUS INTERNAL COMPONENTS
@@ -24,9 +23,5 @@ extern std::optional<HierarchyPreUpdateHandler> hierarchyPreUpdateHandler;
 extern std::optional<HierarchyPostUpdateHandler> hierarchyPostUpdateHandler;
 extern Handles editorToolHandles;
 
-void setSelection(std::vector<std::shared_ptr<Instance>> newSelection, bool fromExplorer = false);
-const std::vector<std::shared_ptr<Instance>> getSelection();
-void addSelectionListener(SelectionUpdateHandler handler);
-
 void sendPropertyUpdatedSignal(std::shared_ptr<Instance> instance, std::string property, Variant newValue);
 void addPropertyUpdateListener(PropertyUpdateHandler handler);

core/src/datatypes/ref.h

@@ -2,12 +2,13 @@
 
 #include "base.h"
 #include "error/data.h"
+#include "utils.h"
 #include <memory>
 
 class Instance;
 
 class InstanceRef {
-    std::shared_ptr<Instance> ref;
+    nullable std::shared_ptr<Instance> ref;
 public:
     InstanceRef();
     InstanceRef(std::weak_ptr<Instance>);

core/src/handles.cpp

@@ -3,6 +3,7 @@
 #include "datatypes/cframe.h"
 #include "datatypes/vector.h"
 #include "math_helper.h"
+#include "objects/service/selection.h"
 #include "partassembly.h"
 #include <glm/ext/scalar_common.hpp>
 #include <memory>
@@ -27,7 +28,8 @@ static rp3d::PhysicsCommon common;
 static rp3d::PhysicsWorld* world = common.createPhysicsWorld();
 
 std::shared_ptr<Part> getHandleAdornee() {
-    for (std::weak_ptr<Instance> inst : getSelection()) {
+    std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+    for (std::weak_ptr<Instance> inst : selection->Get()) {
         if (!inst.expired() && inst.lock()->IsA<Part>())
             return inst.lock()->CastTo<Part>().expect();
     }
@@ -78,7 +80,8 @@ Vector3 handleSize(HandleFace face) {
 
 static int getAABBOfSelection(glm::vec3& pos, glm::vec3& size, glm::vec3& min, glm::vec3& max) {
     int count = 0;
-    for (std::weak_ptr<Instance> inst : getSelection()) {
+    std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+    for (std::weak_ptr<Instance> inst : selection->Get()) {
         if (inst.expired() || !inst.lock()->IsA<Part>()) continue;
         std::shared_ptr<Part> part = inst.lock()->CastTo<Part>().expect();
 
@@ -97,7 +100,8 @@ static int getAABBOfSelection(glm::vec3& pos, glm::vec3& size, glm::vec3& min, g
 }
 
 static std::shared_ptr<Part> getFirstSelectedPart() {
-    for (std::weak_ptr<Instance> inst : getSelection()) {
+    std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+    for (std::weak_ptr<Instance> inst : selection->Get()) {
         if (inst.expired() || !inst.lock()->IsA<Part>()) continue;
         
         return inst.lock()->CastTo<Part>().expect();
@@ -107,7 +111,7 @@ static std::shared_ptr<Part> getFirstSelectedPart() {
 }
 
 CFrame getLocalHandleCFrame(HandleFace face) {
-    PartAssembly assembly = PartAssembly::FromSelection();
+    PartAssembly assembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
 
     Vector3 size;
     if (editorToolHandles.worldMode)
@@ -125,7 +129,7 @@ CFrame getLocalHandleCFrame(HandleFace face) {
 }
 
 CFrame getHandleCFrame(HandleFace face) {
-    PartAssembly assembly = PartAssembly::FromSelection();
+    PartAssembly assembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
 
     if (editorToolHandles.worldMode) {
         return getLocalHandleCFrame(face) + assembly.assemblyOrigin().Position();

core/src/objects/datamodel.cpp

@@ -1,12 +1,12 @@
 #include "datamodel.h"
-#include "base/service.h"
+#include "objects/base/service.h"
 #include "objects/base/instance.h"
 #include "objects/base/refstate.h"
 #include "objects/base/service.h"
 #include "objects/meta.h"
-#include "objects/script/serverscriptservice.h"
+#include "objects/service/script/serverscriptservice.h"
 #include "datatypes/variant.h"
-#include "workspace.h"
+#include "objects/service/workspace.h"
 #include "logger.h"
 #include "panic.h"
 #include <pugixml.hpp>

core/src/objects/joint/jointinstance.cpp

@@ -3,9 +3,9 @@
 #include "datatypes/cframe.h"
 #include "datatypes/ref.h"
 #include "objects/datamodel.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/part.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include <memory>
 #include <reactphysics3d/constraint/FixedJoint.h>
 #include <reactphysics3d/engine/PhysicsWorld.h>

core/src/objects/joint/rotate.cpp

@@ -1,7 +1,7 @@
 #include "rotate.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/part.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include "rendering/renderer.h"
 #include <reactphysics3d/constraint/HingeJoint.h>
 

core/src/objects/joint/rotatev.cpp

@@ -1,7 +1,7 @@
 #include "rotatev.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/part.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include "rendering/renderer.h"
 #include <reactphysics3d/constraint/HingeJoint.h>
 

core/src/objects/joint/snap.cpp

@@ -3,9 +3,9 @@
 #include "datatypes/cframe.h"
 #include "objects/datamodel.h"
 #include "objects/joint/jointinstance.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/part.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include <memory>
 #include <reactphysics3d/constraint/FixedJoint.h>
 #include <reactphysics3d/engine/PhysicsWorld.h>

core/src/objects/joint/weld.cpp

@@ -3,9 +3,9 @@
 #include "datatypes/cframe.h"
 #include "objects/datamodel.h"
 #include "objects/joint/jointinstance.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/part.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include <memory>
 #include <reactphysics3d/constraint/FixedJoint.h>
 #include <reactphysics3d/engine/PhysicsWorld.h>

core/src/objects/meta.cpp

@@ -4,14 +4,15 @@
 #include "objects/joint/rotate.h"
 #include "objects/joint/rotatev.h"
 #include "objects/joint/weld.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/model.h"
 #include "objects/part.h"
 #include "objects/joint/snap.h"
 #include "objects/script.h"
-#include "objects/script/scriptcontext.h"
+#include "objects/service/script/scriptcontext.h"
-#include "objects/script/serverscriptservice.h"
+#include "objects/service/script/serverscriptservice.h"
-#include "objects/workspace.h"
+#include "objects/service/selection.h"
+#include "objects/service/workspace.h"
 #include "objects/datamodel.h"
 
 std::map<std::string, const InstanceType*> INSTANCE_MAP = {
@@ -34,4 +35,5 @@ std::map<std::string, const InstanceType*> INSTANCE_MAP = {
     { "JointsService", &JointsService::TYPE },
     { "ScriptContext", &ScriptContext::TYPE },
     { "ServerScriptService", &ServerScriptService::TYPE },
+    { "Selection", &Selection::TYPE },
 };

core/src/objects/part.cpp

@@ -9,7 +9,7 @@
 #include "objects/joint/rotate.h"
 #include "objects/joint/rotatev.h"
 #include "objects/joint/weld.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/joint/jointinstance.h"
 #include "objects/joint/snap.h"
 #include "rendering/renderer.h"

core/src/objects/part.h

@@ -66,7 +66,6 @@ public:
     DEF_PROP_CATEGORY(APPEARANCE)
     DEF_PROP Color3 color;
     DEF_PROP float transparency = 0.f;
-    bool selected = false;
     
     DEF_PROP_CATEGORY(BEHAVIOR)
     DEF_PROP_(on_update=onUpdated) bool anchored = false;

core/src/objects/script.cpp

@@ -3,8 +3,8 @@
 #include "logger.h"
 #include "objects/base/instance.h"
 #include "objects/base/member.h"
-#include "objects/script/scriptcontext.h"
+#include "objects/service/script/scriptcontext.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include "objects/datamodel.h"
 #include "datatypes/ref.h"
 #include "lua.h" // IWYU pragma: keep

core/src/objects/service/jointsservice.cpp

@@ -1,6 +1,6 @@
 #include "jointsservice.h"
-#include "workspace.h"
+#include "objects/service/workspace.h"
-#include "datamodel.h"
+#include "objects/datamodel.h"
 #include <memory>
 
 JointsService::JointsService(): Service(&TYPE) {

core/src/objects/service/script/serverscriptservice.cpp

@@ -1,6 +1,6 @@
 #include "serverscriptservice.h"
 #include "objects/script.h"
-#include "objects/workspace.h"
+#include "objects/service/workspace.h"
 #include "objects/datamodel.h"
 
 ServerScriptService::ServerScriptService(): Service(&TYPE) {

core/src/objects/service/selection.cpp

@@ -0,0 +1,42 @@
+#include "selection.h"
+#include "objects/datamodel.h"
+#include <algorithm>
+#include <memory>
+
+Selection::Selection(): Service(&TYPE) {
+}
+
+Selection::~Selection() = default;
+
+void Selection::InitService() {
+    if (initialized) return;
+    initialized = true;
+}
+
+std::vector<std::shared_ptr<Instance>> Selection::Get() {
+    return selection;
+}
+
+void Selection::Set(std::vector<std::shared_ptr<Instance>> newSelection) {
+    selection = newSelection;
+    SelectionChanged->Fire();
+}
+
+void Selection::Add(std::vector<std::shared_ptr<Instance>> instances) {
+    for (auto inst : instances) {
+        if (std::find(selection.begin(), selection.end(), inst) == selection.end()) {
+            selection.push_back(inst);
+        }
+    }
+    SelectionChanged->Fire();
+}
+
+void Selection::Remove(std::vector<std::shared_ptr<Instance>> instances) {
+    for (auto inst : instances) {
+        std::vector<std::shared_ptr<Instance>>::iterator p;
+        if ((p = std::find(selection.begin(), selection.end(), inst)) != selection.end()) {
+            selection.erase(p);
+        }
+    }
+    SelectionChanged->Fire();
+}

core/src/objects/service/selection.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include "datatypes/signal.h"
+#include "objects/annotation.h"
+#include "objects/base/service.h"
+#include <memory>
+#include <vector>
+
+class DEF_INST_SERVICE Selection : public Service {
+    AUTOGEN_PREAMBLE
+private:
+    std::vector<std::shared_ptr<Instance>> selection;
+    protected:
+    void InitService() override;
+    bool initialized = false;
+public:
+    Selection();
+    ~Selection();
+    static inline std::shared_ptr<Instance> Create() { return std::make_shared<Selection>(); };
+
+    std::vector<std::shared_ptr<Instance>> Get();
+    void Set(std::vector<std::shared_ptr<Instance>> newSelection);
+
+    void Add(std::vector<std::shared_ptr<Instance>> instances);
+    void Remove(std::vector<std::shared_ptr<Instance>> instances);
+
+    SignalSource SelectionChanged;
+};

core/src/objects/service/workspace.cpp

@@ -3,7 +3,7 @@
 #include "datatypes/ref.h"
 #include "datatypes/vector.h"
 #include "objects/base/instance.h"
-#include "objects/jointsservice.h"
+#include "objects/service/jointsservice.h"
 #include "objects/joint/jointinstance.h"
 #include "objects/datamodel.h"
 #include "physics/util.h"

core/src/partassembly.cpp

@@ -6,6 +6,7 @@
 #include "math_helper.h"
 #include "objects/base/instance.h"
 #include "objects/part.h"
+#include "objects/service/selection.h"
 #include <glm/common.hpp>
 #include <memory>
 #include <vector>
@@ -54,6 +55,10 @@ PartAssembly PartAssembly::FromSelection(std::vector<std::shared_ptr<Instance>>
     return PartAssembly(selection, editorToolHandles.worldMode);
 }
 
+PartAssembly PartAssembly::FromSelection(std::shared_ptr<Selection> selection) {
+    return FromSelection(selection->Get());
+}
+
 void PartAssembly::SetCollisionsEnabled(bool enabled) {
     for (auto part : parts) {
         part->rigidBody->getCollider(0)->setIsWorldQueryCollider(enabled);
@@ -113,3 +118,17 @@ void PartAssembly::Scale(Vector3 newSize, bool scaleUp) {
 
     _bounds = _bounds * factor;
 }
+
+std::vector<PartTransformState> PartAssembly::GetCurrentTransforms() {
+    std::vector<PartTransformState> transforms;
+
+    for (auto part : parts) {
+        PartTransformState t;
+        t.part = part;
+        t.cframe = part->cframe;
+        t.size = part->size;
+        transforms.push_back(t);
+    }
+
+    return transforms;
+}

core/src/partassembly.h

@@ -6,8 +6,13 @@
 
 class Part;
 class Instance;
+class Selection;
 
-const std::vector<std::shared_ptr<Instance>> getSelection();
+struct PartTransformState {
+    std::shared_ptr<Part> part;
+    Vector3 size;
+    CFrame cframe;
+};
 
 class PartAssembly {
     CFrame _assemblyOrigin;
@@ -18,13 +23,17 @@ class PartAssembly {
 public:
     PartAssembly(std::vector<std::shared_ptr<Part>>, bool worldMode = false);
 
-    static PartAssembly FromSelection(std::vector<std::shared_ptr<Instance>> selection = getSelection());
+    static PartAssembly FromSelection(std::vector<std::shared_ptr<Instance>> selection);
+    static PartAssembly FromSelection(std::shared_ptr<Selection> selection);
 
     inline CFrame assemblyOrigin() { return _assemblyOrigin; };
     inline Vector3 bounds() { return _bounds; };
     inline Vector3 size() { return _size; };
     inline bool multipleSelected() { return parts.size() > 1; }
 
+    // Gets the current transform state of all the parts in the assembly
+    std::vector<PartTransformState> GetCurrentTransforms();
+
     // Transforms the assembly such that newOrigin is now this assembly's new assemblyOrigin
     void SetOrigin(CFrame newOrigin);
 

core/src/rendering/renderer.cpp

@@ -19,6 +19,7 @@
 #include "datatypes/vector.h"
 #include "handles.h"
 #include "math_helper.h"
+#include "objects/service/selection.h"
 #include "partassembly.h"
 #include "rendering/torus.h"
 #include "shader.h"
@@ -270,7 +271,7 @@ static CFrame XYZToZXY(glm::vec3(0, 0, 0), -glm::vec3(1, 0, 0), glm::vec3(0, 0,
 void renderHandles() {
     if (!editorToolHandles.active) return;
 
-    auto assembly = PartAssembly::FromSelection();
+    auto assembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
     if (assembly.size() == Vector3::ZERO) return;
 
     glDepthMask(GL_TRUE);
@@ -448,15 +449,12 @@ void renderOutlines() {
 
     glm::vec3 min, max;
     bool first = true;
-    int count = 0;
 
-    for (auto it = gWorkspace()->GetDescendantsStart(); it != gWorkspace()->GetDescendantsEnd(); it++) {
+    std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
-        std::shared_ptr<Instance> inst = *it;
+    for (auto inst : selection->Get()) {
         if (inst->GetClass() != &Part::TYPE) continue;
         std::shared_ptr<Part> part = std::dynamic_pointer_cast<Part>(inst);
-        if (!part->selected) continue;
 
-        count++;
         if (first)
             min = part->position(), max = part->position();
         first = false;
@@ -475,7 +473,7 @@ void renderOutlines() {
     }
 
     // Render AABB of selected parts
-    PartAssembly selectionAssembly = PartAssembly::FromSelection();
+    PartAssembly selectionAssembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
     if (selectionAssembly.size() == Vector3()) return;
     glm::vec3 outlineSize = selectionAssembly.bounds();
     glm::vec3 outlinePos = selectionAssembly.assemblyOrigin().Position();
@@ -498,7 +496,7 @@ void renderSelectionAssembly() {
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
-    PartAssembly selectionAssembly = PartAssembly::FromSelection();
+    PartAssembly selectionAssembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
 
     // Use shader
     outlineShader->use();
@@ -555,7 +553,7 @@ void renderRotationArcs() {
     // Pass in the camera position
     handleShader->set("viewPos", camera.cameraPos);
 
-    PartAssembly assembly = PartAssembly::FromSelection();
+    PartAssembly assembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
 
     for (HandleFace face : HandleFace::Faces) {
         if (glm::any(glm::lessThan(face.normal, glm::vec3(0)))) continue;

core/src/utils.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wnullability-extension"
+#define nullable _Nullable
+#define notnull _Nonnull
+#else
+#define nullable
+#define notnull
+#endif

editor/CMakeLists.txt

@@ -26,6 +26,8 @@ set(PROJECT_SOURCES
         mainglwidget.cpp
         placedocument.h
         placedocument.cpp
+        undohistory.h
+        undohistory.cpp
         panes/explorerview.h
         panes/explorerview.cpp
         panes/explorermodel.h

editor/mainglwidget.cpp

@@ -15,11 +15,13 @@
 #include "math_helper.h"
 #include "objects/base/instance.h"
 #include "objects/pvinstance.h"
+#include "objects/service/selection.h"
 #include "partassembly.h"
 #include "physics/util.h"
 #include "rendering/renderer.h"
 #include "rendering/shader.h"
 #include "datatypes/variant.h"
+#include "undohistory.h"
 
 #define PI 3.14159
 #define M_mainWindow dynamic_cast<MainWindow*>(window())
@@ -119,6 +121,8 @@ CFrame snapCFrame(CFrame frame) {
     return CFrame(frame.Position(), frame.Position() + closestVec1, closestVec2);
 }
 
+std::vector<PartTransformState> initialTransforms;
+
 bool tryMouseContextMenu = false;
 bool isMouseDragging = false;
 std::weak_ptr<Part> draggingObject;
@@ -217,7 +221,7 @@ void MainGLWidget::handleLinearTransform(QMouseEvent* evt) {
         absDiff = handleCFrame.Rotation() * Vector3(0, 0, diff);
     }
 
-    PartAssembly selectionAssembly = PartAssembly::FromSelection();
+    PartAssembly selectionAssembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
 
     if (editorToolHandles.handlesType == MoveHandles) {
         selectionAssembly.TransformBy(CFrame() + absDiff);
@@ -358,6 +362,7 @@ void MainGLWidget::mouseMoveEvent(QMouseEvent* evt) {
 }
 
 void MainGLWidget::mousePressEvent(QMouseEvent* evt) {
+    initialTransforms = {};
     tryMouseContextMenu = evt->button() == Qt::RightButton;
     switch(evt->button()) {
     // Camera drag
@@ -374,8 +379,10 @@ void MainGLWidget::mousePressEvent(QMouseEvent* evt) {
         auto handle = raycastHandle(pointDir);
         if (handle.has_value()) {
             startPoint = glm::vec2(evt->pos().x(), evt->pos().y());
-            initialAssembly = PartAssembly::FromSelection();
+            initialAssembly = PartAssembly::FromSelection(gDataModel->GetService<Selection>());
             initialFrame = initialAssembly.assemblyOrigin();
+            initialTransforms = PartAssembly::FromSelection(gDataModel->GetService<Selection>()).GetCurrentTransforms();
+            printf("%ld\n", initialTransforms.size());
             isMouseDragging = true;
             draggingHandle = handle;
             startLinearTransform(evt);
@@ -383,10 +390,11 @@ void MainGLWidget::mousePressEvent(QMouseEvent* evt) {
         }
 
         // raycast part
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
         std::optional<const RaycastResult> rayHit = gWorkspace()->CastRayNearest(camera.cameraPos, pointDir, 50000);
-        if (!rayHit || !partFromBody(rayHit->body)) { setSelection({}); return; }
+        if (!rayHit || !partFromBody(rayHit->body)) { selection->Set({}); return; }
         std::shared_ptr<Part> part = partFromBody(rayHit->body);
-        if (part->locked) { setSelection({}); return; }
+        if (part->locked) { selection->Set({}); return; }
 
         std::shared_ptr<PVInstance> selObject = part;
 
@@ -428,20 +436,16 @@ void MainGLWidget::mousePressEvent(QMouseEvent* evt) {
         //part.selected = true;
         isMouseDragging = true;
         draggingObject = part;
+        initialTransforms = PartAssembly::FromSelection({part}).GetCurrentTransforms();
         if (evt->modifiers() & (Qt::ControlModifier | Qt::ShiftModifier)) {
-            std::vector<std::shared_ptr<Instance>> currentSelection = getSelection();
+            auto sel = selection->Get();
-            for (size_t i = 0; i < currentSelection.size(); i++) {
+            if (std::find(sel.begin(), sel.end(), selObject) == sel.end())
-                std::shared_ptr<Instance> inst = currentSelection[i];
+                selection->Add({ selObject });
-                if (inst == selObject) {
+            else
-                    currentSelection.erase(currentSelection.begin() + i);
+                selection->Remove({ selObject });
-                    goto skipAddPart;
+        } else {
-                }
+            selection->Set({ selObject });
-            }
+        }
-            currentSelection.push_back(selObject);
-            skipAddPart:
-            setSelection(currentSelection);
-        } else
-            setSelection({ selObject });
         // Disable bit so that we can ignore the part while raycasting
         // part->rigidBody->getCollider(0)->setCollisionCategoryBits(0b10);
 
@@ -458,6 +462,17 @@ void MainGLWidget::mouseReleaseEvent(QMouseEvent* evt) {
     draggingObject = {};
     draggingHandle = std::nullopt;
 
+    if (!initialTransforms.empty()) {
+        UndoState historyState;
+
+        for (auto t : initialTransforms) {
+            historyState.push_back(UndoStatePropertyChanged { t.part, "CFrame", t.cframe, t.part->cframe });
+            historyState.push_back(UndoStatePropertyChanged { t.part, "Size", t.size, t.part->size });
+        }
+
+        M_mainWindow->undoManager.PushState(historyState);
+    }
+
     // Open context menu
     if (tryMouseContextMenu)
         contextMenu.exec(QCursor::pos());
@@ -508,20 +523,8 @@ void MainGLWidget::keyPressEvent(QKeyEvent* evt) {
         }));
         gWorkspace()->SyncPartPhysics(lastPart);
         lastPart->name = "Part" + std::to_string(partId++);
+        M_mainWindow->undoManager.PushState({ UndoStateInstanceCreated { lastPart, gWorkspace() } });
     }
-
-    if (evt->key() == Qt::Key_U)
-        Logger::info("info message");
-    if (evt->key() == Qt::Key_I)
-        Logger::warning("warning message");
-    if (evt->key() == Qt::Key_O)
-        Logger::error("error message");
-
-    if (evt->key() == Qt::Key_C && getSelection().size() > 0)
-        getSelection()[0]->Clone().value()->SetParent(gWorkspace());
-
-    if (evt->key() == Qt::Key_H && getSelection().size() > 0)
-        Logger::infof("Object at: 0x%x\n", getSelection()[0].get());
 }
 
 void MainGLWidget::keyReleaseEvent(QKeyEvent* evt) {

editor/mainwindow.cpp

@@ -5,12 +5,15 @@
 #include "logger.h"
 #include "objects/datamodel.h"
 #include "objects/model.h"
+#include "objects/service/selection.h"
 #include "placedocument.h"
 #include "script/scriptdocument.h"
+#include "undohistory.h"
 #include <memory>
 #include <qclipboard.h>
 #include <qevent.h>
 #include <qglobal.h>
+#include <qkeysequence.h>
 #include <qmessagebox.h>
 #include <qmimedata.h>
 #include <qnamespace.h>
@@ -44,15 +47,6 @@ inline bool isDarkMode() {
 
 QtMessageHandler defaultMessageHandler = nullptr;
 
-// std::map<QtMsgType, Logger::LogLevel> QT_MESSAGE_TYPE_TO_LOG_LEVEL = {
-//     { QtMsgType::QtInfoMsg, Logger::LogLevel::INFO },  
-//     { QtMsgType::QtSystemMsg, Logger::LogLevel::INFO }, 
-//     { QtMsgType::QtDebugMsg, Logger::LogLevel::DEBUG }, 
-//     { QtMsgType::QtWarningMsg, Logger::LogLevel::WARNING }, 
-//     { QtMsgType::QtCriticalMsg, Logger::LogLevel::ERROR }, 
-//     { QtMsgType::QtFatalMsg, Logger::LogLevel::FATAL_ERROR }, 
-// };
-
 void logQtMessage(QtMsgType type, const QMessageLogContext &context, const QString &msg) {
     // Logger::log("[Qt] " + msg.toStdString(), QT_MESSAGE_TYPE_TO_LOG_LEVEL[type]);
     Logger::LogLevel logLevel = type == QtMsgType::QtFatalMsg ? Logger::LogLevel::FATAL_ERROR : Logger::LogLevel::DEBUG;
@@ -77,6 +71,8 @@ MainWindow::MainWindow(QWidget *parent)
     ui->setupUi(this);
     setMouseTracking(true);
 
+    ui->actionRedo->setShortcuts({QKeySequence("Ctrl+Shift+Z"), QKeySequence("Ctrl+Y")});
+
     QIcon::setThemeSearchPaths(QIcon::themeSearchPaths() + QStringList { "./assets/icons" });
     if (isDarkMode())
         QIcon::setFallbackThemeName("editor-dark");
@@ -97,28 +93,6 @@ MainWindow::MainWindow(QWidget *parent)
 
     connectActionHandlers();
 
-    // Update properties
-    addSelectionListener([&](auto oldSelection, auto newSelection, bool fromExplorer) {
-        if (newSelection.size() == 0) return;
-        if (newSelection.size() > 1)
-            ui->propertiesView->setSelected(std::nullopt);
-        ui->propertiesView->setSelected(newSelection[0]);
-    });
-
-    addSelectionListener([&](auto oldSelection, auto newSelection, bool __) {
-        for (std::weak_ptr<Instance> inst : oldSelection) {
-            if (inst.expired() || inst.lock()->GetClass() != &Part::TYPE) continue;
-            std::shared_ptr<Part> part = std::dynamic_pointer_cast<Part>(inst.lock());
-            part->selected = false;
-        }
-
-        for (std::weak_ptr<Instance> inst : newSelection) {
-            if (inst.expired() || inst.lock()->GetClass() != &Part::TYPE) continue;
-            std::shared_ptr<Part> part = std::dynamic_pointer_cast<Part>(inst.lock());
-            part->selected = true;
-        }
-    });
-
     // ui->explorerView->Init(ui);
     placeDocument = new PlaceDocument(this);
     placeDocument->setAttribute(Qt::WA_DeleteOnClose, true);
@@ -126,8 +100,18 @@ MainWindow::MainWindow(QWidget *parent)
     ui->mdiArea->currentSubWindow()->showMaximized();
     ui->mdiArea->findChild<QTabBar*>()->setExpanding(false);
     placeDocument->init();
+    ui->propertiesView->init();
 
     ui->mdiArea->setTabsClosable(true);
+
+    // Undo/Redo
+    ui->actionUndo->setEnabled(false);
+    ui->actionRedo->setEnabled(false);
+
+    undoManager.SetUndoStateListener([&](bool canUndo, bool canRedo) {
+        ui->actionUndo->setEnabled(canUndo);
+        ui->actionRedo->setEnabled(canRedo);
+    });
 }
 
 void MainWindow::closeEvent(QCloseEvent* evt) {
@@ -299,16 +283,22 @@ void MainWindow::connectActionHandlers() {
     });
 
     connect(ui->actionDelete, &QAction::triggered, this, [&]() {
-        for (std::weak_ptr<Instance> inst : getSelection()) {
+        UndoState historyState;
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (std::weak_ptr<Instance> inst : selection->Get()) {
             if (inst.expired()) continue;
+            historyState.push_back(UndoStateInstanceRemoved { inst.lock(), inst.lock()->GetParent().value() });
             inst.lock()->SetParent(std::nullopt);
         }
-        setSelection({});
+        selection->Set({});
+        historyState.push_back(UndoStateSelectionChanged {selection->Get(), {}});
+        undoManager.PushState(historyState);
     });
 
     connect(ui->actionCopy, &QAction::triggered, this, [&]() {
         pugi::xml_document rootDoc;
-        for (std::weak_ptr<Instance> inst : getSelection()) {
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (std::weak_ptr<Instance> inst : selection->Get()) {
             if (inst.expired()) continue;
             inst.lock()->Serialize(rootDoc);
         }
@@ -320,13 +310,20 @@ void MainWindow::connectActionHandlers() {
         mimeData->setData("application/xml", QByteArray::fromStdString(encoded.str()));
         QApplication::clipboard()->setMimeData(mimeData);
     });
+    
     connect(ui->actionCut, &QAction::triggered, this, [&]() {
+        UndoState historyState;
         pugi::xml_document rootDoc;
-        for (std::weak_ptr<Instance> inst : getSelection()) {
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (std::weak_ptr<Instance> inst : selection->Get()) {
             if (inst.expired()) continue;
+            historyState.push_back(UndoStateInstanceRemoved { inst.lock(), inst.lock()->GetParent().value() });
             inst.lock()->Serialize(rootDoc);
             inst.lock()->SetParent(std::nullopt);
         }
+        selection->Set({});
+        historyState.push_back(UndoStateSelectionChanged {selection->Get(), {}});
+        undoManager.PushState(historyState);
 
         std::ostringstream encoded;
         rootDoc.save(encoded);
@@ -337,6 +334,7 @@ void MainWindow::connectActionHandlers() {
     });
 
     connect(ui->actionPaste, &QAction::triggered, this, [&]() {
+        UndoState historyState;
         const QMimeData* mimeData = QApplication::clipboard()->mimeData();
         if (!mimeData || !mimeData->hasFormat("application/xml")) return;
         QByteArray bytes = mimeData->data("application/xml");
@@ -348,14 +346,19 @@ void MainWindow::connectActionHandlers() {
         for (pugi::xml_node instNode : rootDoc.children()) {
             result<std::shared_ptr<Instance>, NoSuchInstance> inst = Instance::Deserialize(instNode);
             if (!inst) { inst.logError(); continue; }
+            historyState.push_back(UndoStateInstanceCreated { inst.expect(), gWorkspace() });
             gWorkspace()->AddChild(inst.expect());
         }
+
+        undoManager.PushState(historyState);
     });
 
     connect(ui->actionPasteInto, &QAction::triggered, this, [&]() {
-        if (getSelection().size() != 1) return;
+        UndoState historyState;
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        if (selection->Get().size() != 1) return;
 
-        std::shared_ptr<Instance> selectedParent = getSelection()[0];
+        std::shared_ptr<Instance> selectedParent = selection->Get()[0];
 
         const QMimeData* mimeData = QApplication::clipboard()->mimeData();
         if (!mimeData || !mimeData->hasFormat("application/xml")) return;
@@ -368,16 +371,22 @@ void MainWindow::connectActionHandlers() {
         for (pugi::xml_node instNode : rootDoc.children()) {
             result<std::shared_ptr<Instance>, NoSuchInstance> inst = Instance::Deserialize(instNode);
             if (!inst) { inst.logError(); continue; }
+            historyState.push_back(UndoStateInstanceCreated { inst.expect(), selectedParent });
             selectedParent->AddChild(inst.expect());
         }
+
+        undoManager.PushState(historyState);
     });
 
     connect(ui->actionGroupObjects, &QAction::triggered, this, [&]() {
+        UndoState historyState;
         auto model = Model::New();
         std::shared_ptr<Instance> firstParent;
         
-        for (auto object : getSelection()) {
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (auto object : selection->Get()) {
             if (firstParent == nullptr && object->GetParent().has_value()) firstParent = object->GetParent().value();
+            historyState.push_back(UndoStateInstanceReparented { object, object->GetParent().value(), model });
             object->SetParent(model);
         }
 
@@ -387,28 +396,35 @@ void MainWindow::connectActionHandlers() {
         // Technically not how it works in the actual studio, but it's not an API-breaking change
         // and I think this implementation is more useful so I'm sticking with it
         if (firstParent == nullptr) firstParent = gWorkspace();
+        historyState.push_back(UndoStateInstanceCreated { model, firstParent });
         model->SetParent(firstParent);
 
-        setSelection({ model });
+        historyState.push_back(UndoStateSelectionChanged { selection->Get(), { model } });
+        selection->Set({ model });
         playSound("./assets/excluded/electronicpingshort.wav");
     });
 
     connect(ui->actionUngroupObjects, &QAction::triggered, this, [&]() {
+        UndoState historyState;
         std::vector<std::shared_ptr<Instance>> newSelection;
 
-        for (auto model : getSelection()) {
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (auto model : selection->Get()) {
             // Not a model, skip
             if (!model->IsA<Model>()) { newSelection.push_back(model); continue; }
 
             for (auto object : model->GetChildren()) {
+                historyState.push_back(UndoStateInstanceReparented { object, object->GetParent().value(), model->GetParent().value() });
                 object->SetParent(model->GetParent());
                 newSelection.push_back(object);
             }
 
-            model->Destroy();
+            historyState.push_back(UndoStateInstanceRemoved { model, model->GetParent().value() });
+            model->SetParent(std::nullopt);
         }
 
-        setSelection(newSelection);
+        historyState.push_back(UndoStateSelectionChanged { selection->Get(), newSelection });
+        selection->Set(newSelection);
         playSound("./assets/excluded/electronicpingshort.wav");
     });
 
@@ -421,7 +437,8 @@ void MainWindow::connectActionHandlers() {
         pugi::xml_document modelDoc;
         pugi::xml_node modelRoot = modelDoc.append_child("openblocks");
 
-        for (std::weak_ptr<Instance> inst : getSelection()) {
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        for (std::weak_ptr<Instance> inst : selection->Get()) {
             if (inst.expired()) continue;
             inst.lock()->Serialize(modelRoot);
         }
@@ -430,8 +447,10 @@ void MainWindow::connectActionHandlers() {
     });
 
     connect(ui->actionInsertModel, &QAction::triggered, this, [&]() {
-        if (getSelection().size() != 1) return;
+        UndoState historyState;
-        std::shared_ptr<Instance> selectedParent = getSelection()[0];
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        if (selection->Get().size() != 1) return;
+        std::shared_ptr<Instance> selectedParent = selection->Get()[0];
 
         std::optional<std::string> path = openFileDialog("Openblocks Model (*.obm)", ".obm", QFileDialog::AcceptOpen);
         if (!path) return;
@@ -443,10 +462,19 @@ void MainWindow::connectActionHandlers() {
         for (pugi::xml_node instNode : modelDoc.child("openblocks").children("Item")) {
             result<std::shared_ptr<Instance>, NoSuchInstance> inst = Instance::Deserialize(instNode);
             if (!inst) { inst.logError(); continue; }
+            historyState.push_back(UndoStateInstanceCreated { inst.expect(), selectedParent });
             selectedParent->AddChild(inst.expect());
         }
     });
 
+    connect(ui->actionUndo, &QAction::triggered, this, [&]() {
+        undoManager.Undo();
+    });
+
+    connect(ui->actionRedo, &QAction::triggered, this, [&]() {
+        undoManager.Redo();
+    });
+
     connect(ui->actionAbout, &QAction::triggered, this, [this]() {
         AboutDialog* aboutDialog = new AboutDialog(this);
         aboutDialog->open();

editor/mainwindow.h

@@ -6,6 +6,7 @@
 #include "qbasictimer.h"
 #include "qcoreevent.h"
 #include "script/scriptdocument.h"
+#include "undohistory.h"
 #include <QMainWindow>
 #include <QLineEdit>
 #include <map>
@@ -50,6 +51,8 @@ public:
     MainWindow(QWidget *parent = nullptr);
     ~MainWindow();
 
+    UndoHistory undoManager;
+    
     SelectedTool selectedTool;
     GridSnappingMode snappingMode;
     bool editSoundEffects = true;
@@ -60,6 +63,8 @@ public:
     void openFile(std::string path);
 
     Ui::MainWindow *ui;
+
+    friend PlaceDocument;
 private:
     PlaceDocument* placeDocument;
     std::map<std::shared_ptr<Script>, ScriptDocument*> scriptDocuments;

editor/mainwindow.ui

@@ -151,6 +151,8 @@
    <addaction name="actionNew"/>
    <addaction name="actionOpen"/>
    <addaction name="actionSave"/>
+   <addaction name="actionUndo"/>
+   <addaction name="actionRedo"/>
   </widget>
   <widget class="QToolBar" name="transformTools">
    <property name="windowTitle">
@@ -816,6 +818,34 @@
     <string>About...</string>
    </property>
   </action>
+  <action name="actionUndo">
+   <property name="icon">
+    <iconset theme="edit-undo"/>
+   </property>
+   <property name="text">
+    <string>Undo</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+Z</string>
+   </property>
+   <property name="menuRole">
+    <enum>QAction::MenuRole::NoRole</enum>
+   </property>
+  </action>
+  <action name="actionRedo">
+   <property name="icon">
+    <iconset theme="edit-redo"/>
+   </property>
+   <property name="text">
+    <string>Redo</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+Y</string>
+   </property>
+   <property name="menuRole">
+    <enum>QAction::MenuRole::NoRole</enum>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>

editor/panes/explorerview.cpp

@@ -5,6 +5,8 @@
 #include "objects/base/instance.h"
 #include "objects/meta.h"
 #include "objects/script.h"
+#include "objects/service/selection.h"
+#include "undohistory.h"
 #include <memory>
 #include <qaction.h>
 #include <qtreeview.h>
@@ -37,6 +39,10 @@ ExplorerView::ExplorerView(QWidget* parent):
     });
 
     connect(selectionModel(), &QItemSelectionModel::selectionChanged, this, [&](const QItemSelection &selected, const QItemSelection &deselected) {
+        // Simple, good old debounce.
+        if (handlingSelectionUpdate)
+            return;
+
         std::vector<std::shared_ptr<Instance>> selectedInstances;
         selectedInstances.reserve(selectedIndexes().count()); // This doesn't reserve everything, but should enhance things anyway
 
@@ -44,20 +50,23 @@ ExplorerView::ExplorerView(QWidget* parent):
             selectedInstances.push_back(reinterpret_cast<Instance*>(index.internalPointer())->shared_from_this());
         }
 
-        ::setSelection(selectedInstances, true);
+        std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
+        selection->Set(selectedInstances);
     });
 
-    addSelectionListener([&](auto oldSelection, auto newSelection, bool fromExplorer) {
+}
-        // It's from us, ignore it.
-        if (fromExplorer) return;
 
-        this->clearSelection();
+void ExplorerView::setSelectedObjects(std::vector<std::shared_ptr<Instance>> selection) {
-        for (std::weak_ptr<Instance> inst : newSelection) {
+    handlingSelectionUpdate = true;
-            if (inst.expired()) continue;
+
-            QModelIndex index = this->model.ObjectToIndex(inst.lock());
+    this->clearSelection();
-            this->selectionModel()->select(index, QItemSelectionModel::SelectionFlag::Select);
+    for (std::weak_ptr<Instance> inst : selection) {
-        }
+        if (inst.expired()) continue;
-    });
+        QModelIndex index = this->model.ObjectToIndex(inst.lock());
+        this->selectionModel()->select(index, QItemSelectionModel::SelectionFlag::Select);
+    }
+
+    handlingSelectionUpdate = false;
 }
 
 ExplorerView::~ExplorerView() {
@@ -103,10 +112,12 @@ void ExplorerView::buildContextMenu() {
         QAction* instAction = new QAction(model.iconOf(type), QString::fromStdString(type->className));
         insertObjectMenu->addAction(instAction);
         connect(instAction, &QAction::triggered, this, [&]() {
-            if (getSelection().size() == 0) return;
+            std::shared_ptr<Selection> selection = gDataModel->GetService<Selection>();
-            std::shared_ptr<Instance> instParent = getSelection()[0];
+            if (selection->Get().size() == 0) return;
+            std::shared_ptr<Instance> instParent = selection->Get()[0];
             std::shared_ptr<Instance> newInst = type->constructor();
             newInst->SetParent(instParent);
+            M_mainWindow->undoManager.PushState({ UndoStateInstanceCreated { newInst, instParent } });
         });
     }
 }

editor/panes/explorerview.h

@@ -1,12 +1,14 @@
 #pragma once
 
 #include "panes/explorermodel.h"
+#include <memory>
 #include <qmenu.h>
 #include <qtreeview.h>
 
 class Ui_MainWindow;
 
 class ExplorerView : public QTreeView {
+    bool handlingSelectionUpdate = false;
 public:
     ExplorerView(QWidget* parent = nullptr);
     ~ExplorerView() override;
@@ -17,6 +19,8 @@ public:
 
     void buildContextMenu();
     void updateRoot(std::shared_ptr<Instance> newRoot);
+
+    void setSelectedObjects(std::vector<std::shared_ptr<Instance>> selection);
 private:
     ExplorerModel model;
     QMenu contextMenu;

editor/panes/propertiesview.cpp

@@ -4,7 +4,9 @@
 #include "datatypes/variant.h"
 #include "datatypes/primitives.h"
 #include "error/data.h"
+#include "mainwindow.h"
 #include "objects/base/member.h"
+#include "undohistory.h"
 
 #include <QColorDialog>
 #include <QComboBox>
@@ -206,6 +208,8 @@ public:
             : view->itemFromIndex(index.parent())->data(0, Qt::DisplayRole).toString().toStdString();
         PropertyMeta meta = inst->GetPropertyMeta(propertyName).expect();
 
+        Variant oldValue = inst->GetProperty(propertyName).expect();
+
         if (isComposite) {
             if (meta.type.descriptor == &Vector3::TYPE) {
                 QDoubleSpinBox* spinBox = dynamic_cast<QDoubleSpinBox*>(editor);
@@ -264,6 +268,9 @@ public:
             model->setData(index, QString::fromStdString(parsedValue.ToString()));
             view->rebuildCompositeProperty(view->itemFromIndex(index), meta.type.descriptor, parsedValue);
         }
+
+        Variant newValue = inst->GetProperty(propertyName).expect();
+        view->undoManager->PushState({ UndoStatePropertyChanged { inst, propertyName, oldValue, newValue } });
     }
 };
 
@@ -300,6 +307,10 @@ QStringList PROPERTY_CATEGORY_NAMES {
     "Surface Inputs",
 };
 
+void PropertiesView::init() {
+    undoManager = &dynamic_cast<MainWindow*>(window())->undoManager;
+}
+
 QModelIndex PropertiesView::indexAt(const QPoint &point) const {
     return QTreeWidget::indexAt(point + QPoint(indentation(), 0));
 }
@@ -402,6 +413,7 @@ void PropertiesView::propertyChanged(QTreeWidgetItem *item, int column) {
 
     if (meta.type.descriptor == &BOOL_TYPE) {
         inst->SetProperty(propertyName, item->checkState(1) == Qt::Checked).expect();
+        undoManager->PushState({ UndoStatePropertyChanged { inst, propertyName, item->checkState(1) != Qt::Checked, item->checkState(1) == Qt::Checked } });
     }
 }
 

editor/panes/propertiesview.h

@@ -3,6 +3,7 @@
 #include <QTreeWidget>
 #include "datatypes/base.h"
 #include "objects/base/instance.h"
+#include "undohistory.h"
 
 class Ui_MainWindow;
 class PropertiesItemDelegate;
@@ -18,6 +19,8 @@ class PropertiesView : public QTreeWidget {
     void rebuildCompositeProperty(QTreeWidgetItem *item, const TypeDesc*, Variant);
     void onPropertyUpdated(std::shared_ptr<Instance> instance, std::string property, Variant newValue);
 
+    UndoHistory* undoManager;
+
     friend PropertiesItemDelegate;
 protected:
     void drawBranches(QPainter *painter, const QRect &rect, const QModelIndex &index) const override;
@@ -26,5 +29,7 @@ public:
     PropertiesView(QWidget* parent = nullptr);
     ~PropertiesView() override;
 
+    void init();
+
     void setSelected(std::optional<std::shared_ptr<Instance>> instance);
 };

editor/placedocument.cpp

@@ -1,10 +1,11 @@
 #include "placedocument.h"
 #include "common.h"
+#include "datatypes/variant.h"
 #include "mainglwidget.h"
 #include "mainwindow.h"
 #include "objects/joint/snap.h"
 #include "objects/script.h"
-#include "objects/script/scriptcontext.h"
+#include "objects/service/script/scriptcontext.h"
 #include "enum/surface.h"
 #include <cstdio>
 #include <memory>
@@ -15,6 +16,8 @@
 #include <qmdisubwindow.h>
 #include <qlayout.h>
 #include <qmimedata.h>
+#include "../ui_mainwindow.h"
+#include "objects/service/selection.h"
 
 PlaceDocument::PlaceDocument(QWidget* parent):
     QMdiSubWindow(parent) {
@@ -24,6 +27,7 @@ PlaceDocument::PlaceDocument(QWidget* parent):
     setWindowTitle("Place");
 
     _runState = RUN_STOPPED;
+    updateSelectionListeners(gDataModel->GetService<Selection>());
 }
 
 PlaceDocument::~PlaceDocument() {
@@ -41,7 +45,7 @@ void PlaceDocument::setRunState(RunState newState) {
         std::shared_ptr<DataModel> newModel = editModeDataModel->CloneModel();
         gDataModel = newModel;
         gDataModel->Init(true);
-        setSelection({});
+        updateSelectionListeners(gDataModel->GetService<Selection>());
     } else if (newState == RUN_PAUSED && _runState == RUN_RUNNING) {
         _runState = RUN_PAUSED;
     } else if (newState == RUN_STOPPED) {
@@ -49,10 +53,28 @@ void PlaceDocument::setRunState(RunState newState) {
 
         // TODO: GC: Check to make sure gDataModel gets properly garbage collected prior to this
         gDataModel = editModeDataModel;
-        setSelection({});
+        updateSelectionListeners(gDataModel->GetService<Selection>());
     }
 }
 
+void PlaceDocument::updateSelectionListeners(std::shared_ptr<Selection> selection) {
+    MainWindow* mainWnd = dynamic_cast<MainWindow*>(window());
+
+    if (!selectionConnection.expired())
+        selectionConnection.lock()->Disconnect();
+
+    selectionConnection = selection->SelectionChanged->Connect([selection, mainWnd](std::vector<Variant> _){
+        // Update properties
+        if (selection->Get().size() != 1)
+            mainWnd->ui->propertiesView->setSelected(std::nullopt);
+        else
+            mainWnd->ui->propertiesView->setSelected(selection->Get()[0]);
+
+        // Update explorer
+        mainWnd->ui->explorerView->setSelectedObjects(selection->Get());
+    });
+}
+
 void PlaceDocument::closeEvent(QCloseEvent *closeEvent) {
     // Placeholder
     closeEvent->ignore();

editor/placedocument.h

@@ -1,10 +1,13 @@
 #pragma once
 
+#include "datatypes/signal.h"
 #include "mainglwidget.h"
 #include <qevent.h>
 #include <qmdisubwindow.h>
 #include <QBasicTimer>
 
+class Selection;
+
 enum RunState {
     RUN_STOPPED,
     RUN_RUNNING,
@@ -15,7 +18,10 @@ class PlaceDocument : public QMdiSubWindow {
     QBasicTimer timer;
     RunState _runState;
 
+    std::weak_ptr<SignalConnection> selectionConnection;
+
     void timerEvent(QTimerEvent*) override;
+    void updateSelectionListeners(std::shared_ptr<Selection>);
 public:
     MainGLWidget* placeWidget;
     PlaceDocument(QWidget* parent = nullptr);

editor/undohistory.cpp

@@ -0,0 +1,74 @@
+#include "undohistory.h"
+#include "common.h"
+#include "objects/service/selection.h"
+
+void UndoHistory::PushState(UndoState state) {
+    if (processingUndo) return; // Ignore PushState requests when changes are initiated by us
+    redoHistory = {};
+
+    if (maxBufferSize != -1 && (int)undoHistory.size() > maxBufferSize)
+        undoHistory.erase(undoHistory.begin(), undoHistory.begin()+maxBufferSize-(int)undoHistory.size()-1);
+
+    undoHistory.push_back(state);
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
+}
+
+void UndoHistory::Undo() {
+    if (undoHistory.size() == 0) return;
+    UndoState state = undoHistory.back();
+    undoHistory.pop_back();
+    redoHistory.push(state);
+
+    processingUndo = true;
+
+    for (UndoStateChange& change : state) {
+        // https://stackoverflow.com/a/63483353
+        if (auto v = std::get_if<UndoStatePropertyChanged>(&change)) {
+            // The old value used to be valid, so it still should be...
+            v->affectedInstance->SetProperty(v->property, v->oldValue).expect();
+        } else if (auto v = std::get_if<UndoStateInstanceCreated>(&change)) {
+            v->instance->SetParent(std::nullopt);
+        } else if (auto v = std::get_if<UndoStateInstanceRemoved>(&change)) {
+            v->instance->SetParent(v->oldParent);
+        } else if (auto v = std::get_if<UndoStateInstanceReparented>(&change)) {
+            v->instance->SetParent(v->oldParent);
+        } else if (auto v = std::get_if<UndoStateSelectionChanged>(&change)) {
+            gDataModel->GetService<Selection>()->Set(v->oldSelection);
+        }
+    }
+
+    processingUndo = false;
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
+}
+
+void UndoHistory::Redo() {
+    if (redoHistory.size() == 0) return;
+    UndoState state = redoHistory.top();
+    redoHistory.pop();
+    undoHistory.push_back(state);
+
+    processingUndo = true;
+
+    for (UndoStateChange& change : state) {
+        // https://stackoverflow.com/a/63483353
+        if (auto v = std::get_if<UndoStatePropertyChanged>(&change)) {
+            // The old value used to be valid, so it still should be...
+            v->affectedInstance->SetProperty(v->property, v->newValue).expect();
+        } else if (auto v = std::get_if<UndoStateInstanceCreated>(&change)) {
+            v->instance->SetParent(v->newParent);
+        } else if (auto v = std::get_if<UndoStateInstanceRemoved>(&change)) {
+            v->instance->SetParent(std::nullopt);
+        } else if (auto v = std::get_if<UndoStateInstanceReparented>(&change)) {
+            v->instance->SetParent(v->newParent);
+        } else if (auto v = std::get_if<UndoStateSelectionChanged>(&change)) {
+            gDataModel->GetService<Selection>()->Set(v->newSelection);
+        }
+    }
+
+    processingUndo = false;
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
+}
+
+void UndoHistory::SetUndoStateListener(UndoStateChangedListener listener) {
+    undoStateListener = listener;
+}

editor/undohistory.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include "datatypes/signal.h"
+#include "datatypes/variant.h"
+#include "objects/base/instance.h"
+#include "utils.h"
+#include <deque>
+#include <memory>
+#include <stack>
+
+struct UndoStatePropertyChanged {
+    std::shared_ptr<Instance> affectedInstance;
+    std::string property;
+    Variant oldValue;
+    Variant newValue;
+};
+
+struct UndoStateInstanceCreated {
+    std::shared_ptr<Instance> instance;
+    std::shared_ptr<Instance> newParent;
+};
+
+struct UndoStateInstanceRemoved {
+    std::shared_ptr<Instance> instance;
+    std::shared_ptr<Instance> oldParent;
+};
+
+struct UndoStateInstanceReparented {
+    std::shared_ptr<Instance> instance;
+    nullable std::shared_ptr<Instance> oldParent;
+    nullable std::shared_ptr<Instance> newParent;
+};
+
+struct UndoStateSelectionChanged {
+    std::vector<std::shared_ptr<Instance>> oldSelection;
+    std::vector<std::shared_ptr<Instance>> newSelection;
+};
+
+typedef std::variant<UndoStatePropertyChanged, UndoStateInstanceCreated, UndoStateInstanceRemoved, UndoStateInstanceReparented, UndoStateSelectionChanged> UndoStateChange;
+typedef std::vector<UndoStateChange> UndoState;
+typedef std::function<void(bool canUndo, bool canRedo)> UndoStateChangedListener;
+
+class UndoHistory  {
+    // Ignore PushState requests
+    bool processingUndo = false;
+    std::deque<UndoState> undoHistory;
+    std::stack<UndoState> redoHistory;
+
+    UndoStateChangedListener undoStateListener;
+public:
+    int maxBufferSize = 100;
+
+    void PushState(UndoState);
+    void Undo();
+    void Redo();
+
+    void SetUndoStateListener(UndoStateChangedListener listener);
+};