AssetBundleGraph.AssetBundleGraphEditorWindow.HandleGraphGUIEvents C# (CSharp) Method

        private void HandleGraphGUIEvents()
        {
            //mouse drag event handling.
            switch (Event.current.type) {
            // draw line while dragging.
            case EventType.MouseDrag: {
                    switch (modifyMode) {
                    case ModifyMode.NONE: {
                            switch (Event.current.button) {
                            case 0:{// left click
                                    if (Event.current.command) {
                                        scalePoint = new ScalePoint(Event.current.mousePosition, NodeGUI.scaleFactor, 0);
                                        modifyMode = ModifyMode.SCALING;
                                        break;
                                    }

                                    selection = new AssetBundleGraphSelection(Event.current.mousePosition);
                                    modifyMode = ModifyMode.SELECTING;
                                    break;
                                }
                            case 2:{// middle click.
                                    scalePoint = new ScalePoint(Event.current.mousePosition, NodeGUI.scaleFactor, 0);
                                    modifyMode = ModifyMode.SCALING;
                                    break;
                                }
                            }
                            break;
                        }
                    case ModifyMode.SELECTING: {
                            // do nothing.
                            break;
                        }
                    case ModifyMode.SCALING: {
                            var baseDistance = (int)Vector2.Distance(Event.current.mousePosition, new Vector2(scalePoint.x, scalePoint.y));
                            var distance = baseDistance / NodeGUI.SCALE_WIDTH;
                            var direction = (0 < Event.current.mousePosition.y - scalePoint.y);

                            if (!direction) distance = -distance;

                            // var before = NodeGUI.scaleFactor;
                            NodeGUI.scaleFactor = scalePoint.startScale + (distance * NodeGUI.SCALE_RATIO);

                            if (NodeGUI.scaleFactor < NodeGUI.SCALE_MIN) NodeGUI.scaleFactor = NodeGUI.SCALE_MIN;
                            if (NodeGUI.SCALE_MAX < NodeGUI.scaleFactor) NodeGUI.scaleFactor = NodeGUI.SCALE_MAX;
                            break;
                        }
                    }

                    HandleUtility.Repaint();
                    Event.current.Use();
                    break;
                }
            }

            // mouse up event handling.
            // use rawType for detect for detectiong mouse-up which raises outside of window.
            switch (Event.current.rawType) {
            case EventType.MouseUp: {
                    switch (modifyMode) {
                    /*
                                select contained nodes & connections.
                            */
                    case ModifyMode.SELECTING: {
                            var x = 0f;
                            var y = 0f;
                            var width = 0f;
                            var height = 0f;

                            if (Event.current.mousePosition.x < selection.x) {
                                x = Event.current.mousePosition.x;
                                width = selection.x - Event.current.mousePosition.x;
                            }
                            if (selection.x < Event.current.mousePosition.x) {
                                x = selection.x;
                                width = Event.current.mousePosition.x - selection.x;
                            }

                            if (Event.current.mousePosition.y < selection.y) {
                                y = Event.current.mousePosition.y;
                                height = selection.y - Event.current.mousePosition.y;
                            }
                            if (selection.y < Event.current.mousePosition.y) {
                                y = selection.y;
                                height = Event.current.mousePosition.y - selection.y;
                            }

                            var activeObjectIds = new List<string>();

                            var selectedRect = new Rect(x, y, width, height);

                            foreach (var node in nodes) {
                                var nodeRect = new Rect(node.GetRect());
                                nodeRect.x = nodeRect.x * NodeGUI.scaleFactor;
                                nodeRect.y = nodeRect.y * NodeGUI.scaleFactor;
                                nodeRect.width = nodeRect.width * NodeGUI.scaleFactor;
                                nodeRect.height = nodeRect.height * NodeGUI.scaleFactor;
                                // get containd nodes,
                                if (nodeRect.Overlaps(selectedRect)) {
                                    activeObjectIds.Add(node.Id);
                                }
                            }

                            foreach (var connection in connections) {
                                // get contained connection badge.
                                if (connection.GetRect().Overlaps(selectedRect)) {
                                    activeObjectIds.Add(connection.Id);
                                }
                            }

                            if (Event.current.shift) {
                                // add current active object ids to new list.
                                foreach (var alreadySelectedObjectId in activeObject.idPosDict.ReadonlyDict().Keys) {
                                    if (!activeObjectIds.Contains(alreadySelectedObjectId)) activeObjectIds.Add(alreadySelectedObjectId);
                                }
                            } else {
                                // do nothing, means cancel selections if nodes are not contained by selection.
                            }

                            Undo.RecordObject(this, "Select Objects");

                            activeObject = RenewActiveObject(activeObjectIds);
                            UpdateActivationOfObjects(activeObject);

                            selection = new AssetBundleGraphSelection(Vector2.zero);
                            modifyMode = ModifyMode.NONE;

                            HandleUtility.Repaint();
                            Event.current.Use();
                            break;
                        }

                    case ModifyMode.SCALING: {
                            modifyMode = ModifyMode.NONE;
                            break;
                        }
                    }
                    break;
                }
            }
        }