Table of Contents

Class Layer

Namespace
Northwoods.Go
Assembly
Northwoods.GoDiagram.WinForms.dll

Layers are how named collections of Parts are drawn in front or behind other collections of Parts in a Diagram.

public class Layer
Inheritance
Layer
Inherited Members

Remarks

Layers can only contain Parts, such as Nodes and Links. They cannot hold GraphObjects directly.

Layers have many properties that control what actions users are permitted to perform involving the parts in the layer. These properties are very much like the similarly named properties on Diagram.

You put a Part into a Layer by assigning LayerName with the name of the Layer. You can use data binding to initialize and remember a Part's layer's name. You can change a Part's layer by modifying its LayerName, which changes its Layer. A Part cannot be in more than one Layer at a time.

Each Diagram starts off with the following list of Layers:

  • "Grid"
  • "ViewportBackground"
  • "Background"
  • "" (the default layer)
  • "Foreground"
  • "ViewportForeground"
  • "Adornment"
  • "Tool"

Layers are drawn and presented in order. Parts are normally put in the default layer.

The "Grid" layer is the furthest back; it also contains "temporary" parts that cannot be selected. Furthermore the "Grid" layer has Pickable set to false so that mouse or touch events and calls to the "Find..." methods do not even consider any parts in that layer.

The "Grid", "Adornment", "Tool", and both "Viewport..." layers are considered IsTemporary. Changes to objects in temporary layers are not recorded by the UndoManager. Parts in temporary layers are not selected. Objects in temporary layers do not receive click events unless you set their IsActionable to true.

Use FindLayer(string) to get the Layer with a particular name. You can add your own layers by calling AddLayerBefore(Layer, Layer) or AddLayerAfter(Layer, Layer) to insert a new layer at a particular place in the z-order, or to re-order existing layers. Parts can be individually z-ordered within a layer by setting ZOrder.

Constructors

Layer()

This constructs an empty Layer; you should set the Name before adding the Layer to a Diagram.

public Layer()

Properties

AllowCopy

Gets or sets whether the user may copy objects in this layer.

public bool AllowCopy { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowDelete

Gets or sets whether the user may delete objects in this layer.

public bool AllowDelete { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowGroup

Gets or sets whether the user may group parts together in this layer.

public bool AllowGroup { get; set; }

Property Value

bool

Remarks

The initial value is true.

Gets or sets whether the user may draw new links in this layer.

public bool AllowLink { get; set; }

Property Value

bool

The initial value is true.

AllowMove

Gets or sets whether the user may move objects in this layer.

public bool AllowMove { get; set; }

Property Value

bool

Remarks

The initial value is true.

Gets or sets whether the user may reconnect existing links in this layer.

public bool AllowRelink { get; set; }

Property Value

bool

The initial value is true.

AllowReshape

Gets or sets whether the user may reshape parts in this layer.

public bool AllowReshape { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowResize

Gets or sets whether the user may resize parts in this layer.

public bool AllowResize { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowRotate

Gets or sets whether the user may rotate parts in this layer.

public bool AllowRotate { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowSelect

Gets or sets whether the user may select objects in this layer.

public bool AllowSelect { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowTextEdit

Gets or sets whether the user may do in-place text editing in this layer.

public bool AllowTextEdit { get; set; }

Property Value

bool

Remarks

The initial value is true.

AllowUngroup

Gets or sets whether the user may ungroup existing groups in this layer.

public bool AllowUngroup { get; set; }

Property Value

bool

Remarks

The initial value is true.

Diagram

This read-only property returns the Diagram that is using this Layer.

public Diagram Diagram { get; }

Property Value

Diagram

IsInDocumentBounds

Gets or sets whether or not a layer is included in the DocumentBounds computation.

public bool IsInDocumentBounds { get; set; }

Property Value

bool

Remarks

Default value is true.

IsTemporary

Gets or sets whether the objects in this layer are considered temporary.

public bool IsTemporary { get; set; }

Property Value

bool

Remarks

Parts in temporary layers are not selectable, and changes to Parts in temporary layers are not recorded in the UndoManager. Objects in temporary layers do not receive click events unless you set their IsActionable to true.

Temporary layers are excluded from bounds calculations, with the exception of the "Tool" layer, so that temporary objects created while dragging are included in the bounds.

Default value is false.

IsViewportAligned

Gets or sets whether this layer enforces its Parts to remain in viewport coordinates.

public bool IsViewportAligned { get; set; }

Property Value

bool

Remarks

Diagrams have two default layers with this set to true: "ViewportBackground" and "ViewportForeground". These layers also have IsInDocumentBounds set to false and IsTemporary set to true. If you set this property on a layer, you may wish to set those properties also.

Parts in viewport coordinate layers will get their positions and scales set automatically, to remain invariantly placed and sized in the viewport.

Instead of position, Parts are placed by setting their Alignment and AlignmentFocus values in the same way they are used in a Spot Panel. However, the Alignment spot, if it is Default as it is by default, will be treated as BottomRight rather than Center as a "Spot" Panel does. The AlignmentFocus spot, if it is Default as it is by default, will be treated as the same Spot as the Alignment without any offset. This is convenient for aligning Parts along the sides of the viewport. If you wish to arrange a Part to be near the side of the viewport at a certain distance, specify that in the Alignment Spot. For example, the following code places the red circle near the bottom right corner, but inset by 10 units from both the right and the bottom sides.

myDiagram.Add(
  new Part {
      LayerName = "ViewportBackground",
      Alignment = new Spot(1, 1, -10, -10)
    }
    .Add(
      new Shape("Circle") { Fill = "red", Width = 20, Height = 20 }
    );

For example usage, see Legends and Titles.

Parts in viewport coordinate layers may have unexpected interactions if they are connected to Parts in non-viewport coordinate layers. Setting this value to true automatically sets IsInDocumentBounds to false.

Name

Gets or sets the name for this layer.

public string Name { get; set; }

Property Value

string

Remarks

The initial value is an empty string, which is also the name of the default layer. The name should be unique among the diagram's Layers.

Opacity

Gets or sets the opacity for all parts in this layer.

public double Opacity { get; set; }

Property Value

double

Remarks

The value must be between 0.0 (fully transparent) and 1.0 (no additional transparency). This value is multiplicative with any existing transparency, for instance from a Brush or image transparency. The default value is 1.

This property, unlike Visible, does not change whether any objects are found by the "Find..." methods.

See Also

Parts

This read-only property returns a read-only collection for this Layer's Parts.

public IReadOnlyCollection<Part> Parts { get; }

Property Value

IReadOnlyCollection<Part>

Remarks

The Parts can be Nodes, Links, Groups, Adornments, or simple Parts.

Pickable

Gets or sets whether methods such as FindElementAt(Point, Func<GraphObject, GraphObject>, Predicate<GraphObject>) find any of the objects in this layer.

public bool Pickable { get; set; }

Property Value

bool

Remarks

The default value is true. When this property is false, all of the "Find..." methods will fail to find parts that are in this layer.

Note that setting pickable to false does not prevent users from selecting nodes. It does prevent them from selecting nodes by clicking on them, but does not prevent selection through other mechanisms such as the DragSelectingTool or SelectAll() or calls to Select(Part).

You can control whether individual GraphObjects are "hittable" by setting Pickable.

See Also

Visible

Gets or sets whether the user may view any of the objects in this layer.

public bool Visible { get; set; }

Property Value

bool

Remarks

The default value is true -- all visible Parts are drawn. When this property is false, all of the "Find..." methods will fail to find parts that are in this layer.

See Also

Methods

FindElementAt(Point, Func<GraphObject, GraphObject>, Predicate<GraphObject>)

A convenience function for FindElementAt<T>(Point, Func<GraphObject, T>, Predicate<T>), returning a GraphObject rather than a specified type.

public GraphObject FindElementAt(Point p, Func<GraphObject, GraphObject> navig = null, Predicate<GraphObject> pred = null)

Parameters

p Point
navig Func<GraphObject, GraphObject>
pred Predicate<GraphObject>

Returns

GraphObject

FindElementAt<T>(Point, Func<GraphObject, T>, Predicate<T>)

Find the front-most GraphObject in this layer at the given point in document coordinates.

public T FindElementAt<T>(Point p, Func<GraphObject, T> navig = null, Predicate<T> pred = null) where T : GraphObject

Parameters

p Point

A Point in document coordinates.

navig Func<GraphObject, T>

A function taking a GraphObject and returning a GraphObject, defaulting to the identity.

pred Predicate<T>

A function taking the GraphObject returned by navig and returning true if that element should be returned, defaulting to a predicate that always returns true.

Returns

T

The first GraphObject in the Z-order, or else null.

Type Parameters

T

Remarks

If Visible is false, this method will not find any elements in this layer. However, Opacity does not affect this method.

FindElementsAt(Point, Func<GraphObject, GraphObject>, Predicate<GraphObject>, ICollection<GraphObject>)

A convenience function for FindElementsAt<T, S>(Point, Func<GraphObject, T>, Predicate<T>, S), returning a collection of GraphObjects rather than a collection of the specified type.

public ICollection<GraphObject> FindElementsAt(Point p, Func<GraphObject, GraphObject> navig = null, Predicate<GraphObject> pred = null, ICollection<GraphObject> coll = null)

Parameters

p Point
navig Func<GraphObject, GraphObject>
pred Predicate<GraphObject>
coll ICollection<GraphObject>

Returns

ICollection<GraphObject>

FindElementsAt<T, S>(Point, Func<GraphObject, T>, Predicate<T>, S)

Return a collection of the GraphObjects of this layer at the given point in document coordinates.

public S FindElementsAt<T, S>(Point p, Func<GraphObject, T> navig = null, Predicate<T> pred = null, S coll = null) where T : GraphObject where S : class, ICollection<T>

Parameters

p Point

A Point in document coordinates.

navig Func<GraphObject, T>

A function taking a GraphObject and returning a GraphObject, defaulting to the identity. If this function returns null, the given GraphObject will not be included in the results.

pred Predicate<T>

A function taking the GraphObject returned by navig and returning true if that element should be returned, defaulting to a predicate that always returns true.

coll S

An optional collection to add the results to.

Returns

S

a collection of GraphObjects that will contain all GraphObjects located at Point p, or else an empty collection. If a collection was passed in, it is returned.

Type Parameters

T
S

Remarks

If Visible is false, this method will not find any elements in this layer. However, Opacity does not affect this method.

FindElementsIn(Rect, Func<GraphObject, GraphObject>, Predicate<GraphObject>, bool, ICollection<GraphObject>)

A convenience function for FindElementsIn<T, S>(Rect, Func<GraphObject, T>, Predicate<T>, bool, S), returning a collection of GraphObjects rather than a collection of the specified type.

public ICollection<GraphObject> FindElementsIn(Rect r, Func<GraphObject, GraphObject> navig = null, Predicate<GraphObject> pred = null, bool partialInclusion = false, ICollection<GraphObject> coll = null)

Parameters

r Rect
navig Func<GraphObject, GraphObject>
pred Predicate<GraphObject>
partialInclusion bool
coll ICollection<GraphObject>

Returns

ICollection<GraphObject>

FindElementsIn<T, S>(Rect, Func<GraphObject, T>, Predicate<T>, bool, S)

Returns a collection of all GraphObjects that are inside or that intersect a given Rect in document coordinates.

public S FindElementsIn<T, S>(Rect r, Func<GraphObject, T> navig = null, Predicate<T> pred = null, bool partialInclusion = false, S coll = null) where T : GraphObject where S : class, ICollection<T>

Parameters

r Rect

A Rect in document coordinates.

navig Func<GraphObject, T>

A function taking a GraphObject and returning a GraphObject, defaulting to the identity. If this function returns null, the given GraphObject will not be included in the results.

pred Predicate<T>

A function taking the GraphObject returned by navig and returning true if that element should be returned, defaulting to a predicate that always returns true.

partialInclusion bool

Whether an element can match if it merely intersects the rectangular area (true) or if it must be entirely inside the rectangular area (false). The default value is false.

coll S

An optional collection to add the results to.

Returns

S

a collection of GraphObjects that will contain all GraphObjects located in or near Rect r, or else an empty collection. If a collection was passed in, it is returned.

Type Parameters

T
S

Remarks

If Visible is false, this method will not find any elements in this layer. However, Opacity does not affect this method.

FindElementsNear(Point, double, Func<GraphObject, GraphObject>, Predicate<GraphObject>, bool, ICollection<GraphObject>)

A convenience function for FindElementsNear<T, S>(Point, double, Func<GraphObject, T>, Predicate<T>, bool, S), returning a collection of GraphObjects rather than a collection of the specified type.

public ICollection<GraphObject> FindElementsNear(Point p, double dist, Func<GraphObject, GraphObject> navig = null, Predicate<GraphObject> pred = null, bool partialInclusion = true, ICollection<GraphObject> coll = null)

Parameters

p Point
dist double
navig Func<GraphObject, GraphObject>
pred Predicate<GraphObject>
partialInclusion bool
coll ICollection<GraphObject>

Returns

ICollection<GraphObject>

FindElementsNear<T, S>(Point, double, Func<GraphObject, T>, Predicate<T>, bool, S)

Returns a collection of all GraphObjects that are within a certain distance of a given point in document coordinates.

public S FindElementsNear<T, S>(Point p, double dist, Func<GraphObject, T> navig = null, Predicate<T> pred = null, bool partialInclusion = true, S coll = null) where T : GraphObject where S : class, ICollection<T>

Parameters

p Point

A Point in document coordinates.

dist double

The distance from the point.

navig Func<GraphObject, T>

A function taking a GraphObject and returning a GraphObject, defaulting to the identity. If this function returns null, the given GraphObject will not be included in the results.

pred Predicate<T>

A function taking the GraphObject returned by navig and returning true if that element should be returned, defaulting to a predicate that always returns true.

partialInclusion bool

Whether an element can match if it merely intersects the circular area (true) or if it must be entirely inside the circular area (false). The default value is true.

coll S

An optional collection to add the results to.

Returns

S

a collection of GraphObjects that will contain all GraphObjects located at Point p, or else an empty collection. If a collection was passed in, it is returned.

Type Parameters

T
S

Remarks

If Visible is false, this method will not find any elements in this layer. However, Opacity does not affect this method.