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GoJS® Diagramming Components
version 1.8.23 for JavaScript/HTML
by Northwoods Software®

## Class Group

Extends Node. A Group is a Node that can contain a subgraph of Nodes and Links, which are members of the group.

For more discussion, see Introduction to Groups. See samples that make use of Groups in the samples index.

Although you can create a Group and Diagram.add it to a Diagram, this does not update the Model. It is more common to create a group by adding a node data object to the model by calling Model.addNodeData. For example:

      myDiagram.startTransaction("make new group");
      myDiagram.model.addNodeData({ key: "Omega", isGroup: true });
      myDiagram.commitTransaction("make new group");

This will cause a Group to be created (copying the template found in Diagram.groupTemplateMap), added to the Diagram in some Layer (based on Part.layerName), and bound to the group data (resulting in Panel.data referring to that group data object). Note that the JavaScript object includes setting `isGroup` to true, to indicate that the object represents a Group rather than a regular Node or simple Part.

The member Parts of a Group, which you can access as the memberParts collection, belong to the group but are not in the visual tree of the group. All Parts are directly in Layers -- they cannot be inside a Panel. This allows group member parts to be in layers different from the group's layer.

You can change the membership of a Node or a simple Part in a Group by setting its Part.containingGroup property. This is done automatically for you by the diagram if you initialize the `group` property on the node data in the model to be the key of the containing group node data. Thus you should do something like:

      myDiagram.startTransaction("add new member");
      myDiagram.model.addNodeData({ group: someexistinggroup.data.key, ... });
      myDiagram.commitTransaction("add new member");

where you would make sure the node data object included all of the properties you need. You can also change the relationship dynamically by calling GraphLinksModel.setGroupKeyForNodeData.

The membership of Links is computed automatically for you by the diagram based on the membership of the connected Nodes. For example, if the Link.fromNode is a top-level node but the Link.toNode is a member of a group, the link is a top-level link. If the two connected nodes both belong to the same group, the link is a member of that group. If the two connected nodes belong to different groups, the link belongs to the common container group, if there is any. Note that if a link connects a member of a group with the group itself, the link is a member of that group.

All of the group-member relationships effectively form a tree structure. These properties and methods are useful in navigating these relationships:

- Part.containingGroup
- Part.isTopLevel
- Part.findTopLevelPart
- Part.findSubGraphLevel
- Part.findCommonContainingGroup
- memberParts
- findSubGraphParts
- findExternalLinksConnected
- findExternalNodesConnected

As the membership of a group changes, you may want to update the appearance of the group. You can set the memberAdded and memberRemoved properties to be functions that are called. These functions must not modify any membership relationships -- these function properties just exist to update the appearance of the Group.

You can control whether certain Nodes are added to a Group by CommandHandler.groupSelection or addMembers or CommandHandler.addTopLevelParts by affecting the result of CommandHandler.isValidMember, which is responsible for deciding whether it is OK to add a Node to a Group or to remove a Node from a Group to be a top-level node. You can override that predicate on CommandHandler, but it is easier to set the memberValidation or CommandHandler.memberValidation functional property.

For a more general discussion of validation, see Introduction to Validation.

The area occupied by the subgraph is represented in the group's visual tree by a Placeholder. As the group placeholder grows and shrinks based on the sizes and positions of the member nodes and links, the group will grow and shrink accordingly. The placeholder is always the Part.locationObject, although you may specify any Spot as the Part.locationSpot. A Group need not have a placeholder, but it may have at most one.

A group has its own layout property that is used to position the member nodes and route the member links.

The Group class also supports the notion of expanding and collapsing the subgraph, causing the member nodes and links to be shown or hidden. Principally this is a matter of setting isSubGraphExpanded. Changes to this property will result in calls to collapseSubGraph or expandSubGraph, as appropriate.

If you want to change the appearance of the group you can do so in a function that you assign to the subGraphExpandedChanged property. This function must not modify any member relationships or expand or collapse any groups -- the functional property just exists to update the appearance of the Group.

For more discussion and examples, see SubGraphs.

If you want the user to be able to create a Group out of the currently selected Parts using the CommandHandler.groupSelection command, you need to first set the CommandHandler.archetypeGroupData property to a data object with `isGroup` set to true. If you want the user to be able to ungroup a Group, using the CommandHandler.ungroupSelection command, you need to set ungroupable to true.

For more discussion and examples, see Groups, SubGraphs, and Sized Groups.

Only Groups that are in Diagrams can have member Parts or connections via Links. Templates should not be connected with Links, be labels of Links, be members of Groups, have any member Parts, or have any Adornments.

## Constructor Summary Details

Name | Description
--- | ---
Group(type) | Constructs an empty Group with no visual elements and no member parts; normally a Group will have some visual elements surrounding a Placeholder.More... Parameters: {EnumValue=} type if not supplied, the default Panel type is Panel.Position.

## Properties Summary Details

Name, Value Type | Description
--- | ---
computesBoundsAfterDrag {boolean} | Gets or sets whether the size of the area of the Group's placeholder should remain the same during a DraggingTool move until a drop occurs.More... In other words, when the value is true, re-computing the bounds of the members is suspended until a drop occurs, at which time the border is recomputed, perhaps not including some members that had been dragged out and reparented. The initial value is false.
computesBoundsIncludingLinks {boolean} | Gets or sets whether a placeholder's bounds includes the bounds of member Links.More... The default value is true. If this is false, only non-Link member Parts are used to compute the Placeholder's bounds in document coordinates.
computesBoundsIncludingLocation {boolean} | Gets or sets whether a placeholder's bounds includes the previous Group.location.More... The default value is false.
handlesDragDropForMembers {boolean} 1.5 | Gets or sets whether drag-and-drop events may be bubbled up to this Group if not handled by member Parts.More... The default value is false -- each Node or Link that is a member of the Group needs to define its own GraphObject.mouseDragEnter, GraphObject.mouseDragLeave, and GraphObject.mouseDrop event handlers if you want dragging/dropping on a member part to act as if the user were acting on the group. This is currently restricted to only call the mouseDragEnter, mouseDragLeave, and mouseDrop event handlers defined on the whole Group, not on any element inside the Group's visual tree.
isSubGraphExpanded {boolean} | Gets or sets whether the subgraph contained by this group is expanded.More... Changing this property's value will call collapseSubGraph or expandSubGraph, and also will call the value of subGraphExpandedChanged if it is a function. The initial value is true -- this group's member parts are shown. There is an analogous property for expanded/collapsed trees of Nodes and Links: Node.isTreeExpanded.
layout {Layout} | Gets or sets the Layout used to position all of the immediate member nodes and links in this group.More... By default this property is an instance of Layout -- no special layout is used, which just makes sure each member node has a valid location.
memberAdded {function(Group, Part) | null} | Gets or sets the function that is called after a member Part has been added to this Group.More... It is typically used to modify the appearance of the group. The first argument will be this Group. The second argument will be a Part, typically a Node, but may be a simple Part or a Link. If the value is a function, that function must not modify any membership relationships. The member Part has already been added -- trying to remove it or adding or removing another member or the Group itself may produce undefined behavior. The default value is null -- no function is called.
memberParts {Iterator.} | This read-only property returns an iterator over the member Parts of this Group.More... Setting Part.containingGroup to refer to this Group will add that part to this collection. The Parts can be Nodes, Links, Groups, or simple Parts. A template should not have any member parts.
memberRemoved {function(Group, Part) | null} | Gets or sets the function that is called after a member Part has been removed from this Group.More... It is typically used to modify the appearance of the group. The first argument will be this Group. The second argument will be a Part, typically a Node, but may be a simple Part or a Link. If the value is a function, that function must not modify any membership relationships. The member Part has already been removed -- trying to add it or adding or removing another member or the Group itself may produce undefined behavior. The default value is null -- no function is called.
memberValidation {function(Group, Part):boolean | null} | Gets or sets the predicate that determines whether or not a Part may become a member of this group.More... If this is non-null, the predicate is called in addition to any CommandHandler.memberValidation predicate. The default predicate is null, which is equivalent to simply returning true. The first argument will be this Group. The second argument will be a Part, typically a Node, but will not be a Link or an Adornment. The function, if supplied, must not have any side-effects.
placeholder {Placeholder} | This read-only property returns a Placeholder that this group may contain in its visual tree.
subGraphExpandedChanged {function(Group) | null} | Gets or sets the function that is called when isSubGraphExpanded has changed value.More... The argument to that function will be this Group. If the value is a function, that function must not expand or collapse any groups. The Group has already been expanded or collapsed -- trying to change it again may produce undefined behavior. The default value is null -- no function is called.
ungroupable {boolean} | Gets or sets whether the user may ungroup this group.More... The initial value is false. See also: canUngroup
wasSubGraphExpanded {boolean} | Gets or sets whether the subgraph starting at this group had been collapsed by a call to expandSubGraph on the containing Group.More... The initial value is false. See also: isSubGraphExpanded

Properties borrowed from class Node:
  avoidable, avoidableMargin, isLinkLabel, isTreeExpanded, isTreeLeaf, labeledLink, linkConnected, linkDisconnected, linksConnected, linkValidation, port, ports, portSpreading, SpreadingEvenly, SpreadingNone, SpreadingPacked, treeExpandedChanged, wasTreeExpanded
Properties borrowed from class Part:
  adornments, category, containingGroup, containingGroupChanged, copyable, deletable, diagram, dragComputation, groupable, highlightedChanged, isAnimated, isHighlighted, isInDocumentBounds, isLayoutPositioned, isSelected, isShadowed, isTopLevel, key, layer, layerChanged, layerName, LayoutAdded, layoutConditions, LayoutGroupLayout, LayoutHidden, LayoutNodeReplaced, LayoutNodeSized, LayoutNone, LayoutRemoved, LayoutShown, LayoutStandard, location, locationObject, locationObjectName, locationSpot, maxLocation, minLocation, movable, reshapable, resizable, resizeAdornmentTemplate, resizeCellSize, resizeObject, resizeObjectName, rotatable, rotateAdornmentTemplate, rotateObject, rotateObjectName, selectable, selectionAdorned, selectionAdornmentTemplate, selectionChanged, selectionObject, selectionObjectName, shadowBlur, shadowColor, shadowOffset, text, textEditable, zOrder
Properties borrowed from class Panel:
  alignmentFocusName, Auto, columnCount, columnSizing, data, defaultAlignment, defaultColumnSeparatorDashArray, defaultColumnSeparatorStroke, defaultColumnSeparatorStrokeWidth, defaultRowSeparatorDashArray, defaultRowSeparatorStroke, defaultRowSeparatorStrokeWidth, defaultSeparatorPadding, defaultStretch, elements, Graduated, graduatedMax, graduatedMin, graduatedRange, graduatedTickBase, graduatedTickUnit, Grid, gridCellSize, gridOrigin, Horizontal, isClipping, isEnabled, isOpposite, itemArray, itemCategoryProperty, itemIndex, itemTemplate, itemTemplateMap, leftIndex, Link, padding, Position, rowCount, rowSizing, Spot, Table, TableColumn, TableRow, topIndex, type, Vertical, Viewbox, viewboxStretch
Properties borrowed from class GraphObject:
  actionCancel, actionDown, actionMove, actionUp, actualBounds, alignment, alignmentFocus, angle, areaBackground, background, click, column, columnSpan, contextClick, contextMenu, cursor, Default, desiredSize, doubleClick, enabledChanged, Fill, fromEndSegmentLength, fromLinkable, fromLinkableDuplicates, fromLinkableSelfNode, fromMaxLinks, fromShortLength, fromSpot, height, isActionable, isPanelMain, margin, maxSize, measuredBounds, minSize, mouseDragEnter, mouseDragLeave, mouseDrop, mouseEnter, mouseHold, mouseHover, mouseLeave, mouseOver, name, naturalBounds, None, opacity, panel, part, pickable, portId, position, row, rowSpan, scale, segmentFraction, segmentIndex, segmentOffset, segmentOrientation, shadowVisible, stretch, toEndSegmentLength, toLinkable, toLinkableDuplicates, toLinkableSelfNode, toMaxLinks, toolTip, toShortLength, toSpot, Uniform, UniformToFill, visible, width

## Method Summary Details

Name, Return Type | Description
--- | ---
addMembers(coll, check) {boolean} | Add the Parts in the given collection as members of this Group for those Parts for which CommandHandler.isValidMember returns true.More... If the check argument to this method is not supplied or false, this will set Part.containingGroup on each part unconditionally, not calling CommandHandler.isValidMember. The CommandHandler predicate will use CommandHandler.memberValidation and memberValidation, if either or both are defined. At this time there is no "removeMembers" method. If you want to make a collection of Parts to be top-level parts, not members of any Group but still in the Diagram, call CommandHandler.addTopLevelParts. If you want to remove a collection of Parts not only from a Group but from the whole Diagram, call Diagram.removeParts. Parameters: {Iterable.} coll {boolean=} check whether to call CommandHandler.isValidMember to confirm that it is valid to add the Part to be a member of this Group. Returns: {boolean} true if all non-Links were added to this Group; false if some Parts or Nodes were not able to be added.
canAddMembers(coll) {boolean} | See if the given collection of Parts contains non-Links all for which CommandHandler.isValidMember returns true.More... The CommandHandler predicate will use CommandHandler.memberValidation and memberValidation, if either or both are defined. Parameters: {Iterable.} coll Returns: {boolean} true.
canUngroup() {boolean} | This predicate returns true if ungroupable is true, if the layer's Layer.allowUngroup is true, and if the diagram's Diagram.allowUngroup is true. Returns: {boolean} true if the user may ungroup this object.
collapseSubGraph() | Hide each of the member nodes and links of this group, and recursively collapse any member groups.More... This changes the value of Part.isVisible of the whole subgraph and the parts owned by those member nodes and links. However, this group's visibility is unchanged. This sets isSubGraphExpanded to false on this group and on all of the nested Groups. For those nested Groups that were expanded, wasSubGraphExpanded is set to true. To collapse trees made of Nodes and Links, use Node.collapseTree.
expandSubGraph() | Show each member node and link, and perhaps recursively expand nested subgraphs.More... This may change the value of Part.isVisible of the whole subgraph and the parts owned by those member nodes and links. However, this group's visibility is unchanged. This sets isSubGraphExpanded to true on this group and on all of the nested Groups. This will expand a nested group only if its wasSubGraphExpanded property was true. To expand trees made of Nodes and Links, use Node.expandTree.
findExternalLinksConnected() {Iterator.} 1.3 | Returns an iterator over all of the Links that connect with this group or any node contained by this group, in either direction, but that are not internal to this group.More... Links that are contained by this group (even in nested groups) are not included in the result collection. See also: Node.findLinksConnected Returns: {Iterator.}
findExternalNodesConnected() {Iterator.} 1.3 | Returns an iterator over all of the Nodes that are connected with this group or any node contained by this group, by a link in either direction, but that are not internal to this group.More... Nodes that are contained by this group (even in nested groups) are not included in the result collection. However this group itself might be in the results if there is a reflexive link connected to this group. See also: Node.findNodesConnected Returns: {Iterator.}
findSubGraphParts() {Set.} | Return a collection of Parts that are all of the nodes and links that are members of this group, including inside nested groups, but excluding this group itself.More... For member nodes that are Groups, this will include its members recursively. If you want only the immediate members of this group, use the memberParts property. If you want to find the collection of Nodes and Links that are in the subtree of a given Node, use Node.findTreeParts. Returns: {Set.}
move(newpos) | Move this Group and all of its member parts, recursively.More... Parameters: {Point} newpos a new Point in document coordinates.

Methods borrowed from class Node:
  collapseTree, expandTree, findCommonTreeParent, findLinksBetween, findLinksConnected, findLinksInto, findLinksOutOf, findLinksTo, findNodesConnected, findNodesInto, findNodesOutOf, findPort, findTreeChildrenLinks, findTreeChildrenNodes, findTreeLevel, findTreeParentChain, findTreeParentLink, findTreeParentNode, findTreeParts, findTreeRoot, isInTreeOf
Methods borrowed from class Part:
  addAdornment, canCopy, canDelete, canEdit, canGroup, canLayout, canMove, canReshape, canResize, canRotate, canSelect, clearAdornments, ensureBounds, findAdornment, findCommonContainingGroup, findSubGraphLevel, findTopLevelPart, invalidateLayout, isMemberOf, isVisible, moveTo, removeAdornment, updateAdornments, updateRelationshipsFromData, updateTargetBindings
Methods borrowed from class Panel:
  add, copy, elt, findColumnForLocalX, findItemPanelForData, findMainElement, findObject, findRowForLocalY, getColumnDefinition, getRowDefinition, graduatedPointForValue, graduatedValueForPoint, insertAt, rebuildItemElements, remove, removeAt, removeColumnDefinition, removeRowDefinition
Methods borrowed from class GraphObject:
  bind, getDocumentAngle, getDocumentPoint, getDocumentScale, getLocalPoint, isContainedBy, isEnabledObject, isVisibleObject, setProperties