Class UndoManager

The UndoManager class observes and records model changes and supports undo and redo operations.

Inheritance

UndoManager

Namespace: StockSharp.Xaml.Diagram.GXDiagram.Model

Assembly: StockSharp.Xaml.Diagram.dll

Syntax

public class UndoManager : Object

Constructors

UndoManager()

Create a UndoManager that is ready to record model modifications, but that does not know about any models yet.

Declaration

public UndoManager()

Properties

ChecksTransactionLevel

Gets or sets whether this undo manager will output warnings to Trace listeners when model changes occur outside of a transaction.

Declaration

public bool ChecksTransactionLevel { get; set; }

Property Value

Type	Description
Boolean	This defaults to false.

CompoundEdits

Gets a list of all of the compound edits.

Declaration

public IList<IUndoableEdit> CompoundEdits { get; }

Property Value

Type	Description
IList<IUndoableEdit>	This will be a `List` of mostly UndoManager.CompoundEdits

CurrentEdit

Gets the current compound edit for recording additional model change events.

Declaration

public UndoManager.CompoundEdit CurrentEdit { get; set; }

Property Value

Type	Description
UndoManager.CompoundEdit

Remarks

This is initialized and augmented by HandleModelChanged(Object, ModelChangedEventArgs) before it is added to CompoundEdits by a top-level call to CommitTransaction(String).

CurrentTransactionName

Gets the current transaction name given by StartTransaction(String).

Declaration

public string CurrentTransactionName { get; }

Property Value

Type	Description
String	If no transaction is ongoing, this will be an empty string.

EditToRedo

Gets the current IUndoableEdit to be redone, or null if there is none.

Declaration

public IUndoableEdit EditToRedo { get; }

Property Value

Type	Description
IUndoableEdit

EditToUndo

Gets the current IUndoableEdit to be undone, or null if there is none.

Declaration

public IUndoableEdit EditToUndo { get; }

Property Value

Type	Description
IUndoableEdit

IsUndoingRedoing

This property is true during a call to Undo() or Redo().

Declaration

public bool IsUndoingRedoing { get; protected set; }

Property Value

Type	Description
Boolean

Remarks

When this property is true, CanUndo() and CanRedo() will be false. To avoid confusion, HandleModelChanged(Object, ModelChangedEventArgs) ignores all model change events when this property is true.

MaximumEditCount

Gets or sets the maximum number of compound edits that this undo manager will remember.

Declaration

public int MaximumEditCount { get; set; }

Property Value

Type	Description
Int32	If the value is negative, no limit is assumed. A new value of zero is treated as if the new value were one. The initial value is 999.

Remarks

This property is useful in helping limit the memory consumption of typical application usage. But note that this only limits the number of compound edits, not the size of any individual UndoManager.CompoundEdit, which may still have an unlimited number of ModelChangedEventArgss.

Decreasing this value will not necessarily remove any existing edits if there currently exist more edits in CompoundEdits than the new value would allow.

Models

Gets a list of models for which this UndoManager is recording undo/redo information.

Declaration

public IEnumerable<IDiagramModel> Models { get; }

Property Value

Type	Description
IEnumerable<IDiagramModel>

Remarks

You can manipulate this list explicitly by calling AddModel(IDiagramModel) and RemoveModel(IDiagramModel). Setting UndoManager automatically calls these methods. Undo() and Redo() use this list to call RaiseChanged(ModelChangedEventArgs) with notices about starting and ending undo and redo actions, and about starting/finishing/rollingback edits.

NestedTransactionNames

Gets a stack of ongoing transaction names.

Declaration

public IList<string> NestedTransactionNames { get; }

Property Value

Type	Description
IList<String>

Remarks

The outermost transaction name will be the first item in the list. The last one will be the name of the most recent (nested) call to StartTransaction(String).

TransactionLevel

Gets the current transaction level.

Declaration

public int TransactionLevel { get; protected set; }

Property Value

Type	Description
Int32	This value is zero when no transaction is in progress. The initial value is zero. StartTransaction(String) will increment this value; EndTransaction(Boolean, String) will decrement it. When this value is greater than zero, CanUndo() and CanRedo() will be false, because additional logically related model change events may occur.

UndoEditIndex

Gets the index into CompoundEdits for the current undoable edit.

Declaration

public int UndoEditIndex { get; protected set; }

Property Value

Type	Description
Int32	-1 if there's no undoable edit to be undone.

Methods

AddModel(IDiagramModel)

Make sure this undo manager knows about a IDiagramModel for which it is receiving model Changed event notifications.

Declaration

public virtual void AddModel(IDiagramModel model)

Parameters

Type	Name	Description
IDiagramModel	model

Remarks

This just adds model to the list of Models.

CanRedo()

This predicate is true when one can call Redo().

Declaration

public virtual bool CanRedo()

Returns

Type	Description
Boolean

Remarks

In order to be able to perform a redo, a transaction must not be in progress, nor an undo or a redo. Furthermore there must be an EditToRedo that itself is ready to be redone, because its CanRedo() predicate is true.

CanUndo()

This predicate is true when one can call Undo().

Declaration

public virtual bool CanUndo()

Returns

Type	Description
Boolean

Remarks

In order to be able to perform an undo, a transaction must not be in progress, nor an undo or a redo. Furthermore there must be an EditToUndo that itself is ready to be undone, because its CanUndo() predicate is true.

Clear()

Clear all of the UndoManager.CompoundEdits and reset all other state.

Declaration

public virtual void Clear()

Remarks

However, this does not forget the models that this undo manager is managing.

CommitCompoundEdit(UndoManager.CompoundEdit)

This method is called by EndTransaction(Boolean, String) when committing a compound edit.

Declaration

protected virtual UndoManager.CompoundEdit CommitCompoundEdit(UndoManager.CompoundEdit cedit)

Parameters

Type	Name	Description
UndoManager.CompoundEdit	cedit	the CurrentEdit; this may be null if there had been no changes at commit time

Returns

Type	Description
UndoManager.CompoundEdit	By default, the unmodified `cedit`.

Remarks

You may wish to override this method in order to perform optimizations, such as removing duplicate or unnecessary ModelChangedEventArgss.

CommitTransaction(String)

Just call EndTransaction(Boolean, String), committing the current transaction, with the presentation name for the transaction.

Declaration

public bool CommitTransaction(string tname)

Parameters

Type	Name	Description
String	tname	the transaction name

Returns

Type	Description
Boolean	the value of the call to EndTransaction(Boolean, String)

EndTransaction(Boolean, String)

Stop the current transaction, either rolling it back or committing it.

Declaration

protected virtual bool EndTransaction(bool commit, string tname)

Parameters

Type	Name	Description
Boolean	commit	true to terminate the transaction normally; false to abort it and rollback the existing edits
String	tname	the internal locale-neutral name for the transaction

Returns

Type	Description
Boolean	true for a committed top-level transaction

Remarks

If this call stops a top-level transaction, a value of false for commit just undoes and discards the information in the CurrentEdit. If commit is true for a top-level transaction, we mark the CurrentEdit complete, call CommitCompoundEdit(UndoManager.CompoundEdit), and add the resulting UndoManager.CompoundEdit to the list of compound edits that this undo manager is recording.

Committing a transaction when there have been some undos without corresponding redos will throw away the compound edits holding changes that happened after the current state, before adding this new compound edit to the undo manager's list of edits.

This method raises a Changed event for each of this undo manager's Models, with a hint of CommittedTransaction, and with a OldValue that is the UndoManager.CompoundEdit that has been added to the list of CompoundEdits. Similarly, if the transaction is aborted, either because commit is false or because there is no CurrentEdit to commit, all of the Models get a RolledBackTransaction Changed event. The values passed in the ModelChangedEventArgs may all be null, however.

FindPrimaryObject(IUndoableEdit)

Given an IUndoableEdit return an edited object that represents what was modified.

Declaration

public virtual object FindPrimaryObject(IUndoableEdit edit)

Parameters

Type	Name	Description
IUndoableEdit	edit	an IUndoableEdit, usually either a ModelChangedEventArgs or a UndoManager.CompoundEdit

Returns

Type	Description
Object	typically a StockSharp.Xaml.Diagram.GXDiagram.Node or a StockSharp.Xaml.Diagram.GXDiagram.Link, but this may be null if there is no such object, perhaps because a model property was modified, or because there were no real edits in the argument `edit`.

HandleModelChanged(Object, ModelChangedEventArgs)

Create an IUndoableEdit for a Changed event.

Declaration

public virtual void HandleModelChanged(object sender, ModelChangedEventArgs e)

Parameters

Type	Name	Description
Object	sender
ModelChangedEventArgs	e

Remarks

This calls SkipEvent(ModelChangedEventArgs) if for some reason we should ignore the e. This then creates a ModelChangedEventArgs and adds it to the CurrentEdit, a UndoManager.CompoundEdit which it allocates if needed. This method always ignores all Changed events while we are performing an Undo() or Redo().

Redo()

Restore the state of some models to after the current IUndoableEdit.

Declaration

public virtual void Redo()

Remarks

This calls Redo() on the current EditToRedo. This will raise a Changed event with a hint of StartingRedo before actually performing the redo, and will raise a Changed event with a hint of FinishedRedo afterwards. The Data is the UndoManager.CompoundEdit that was the value of EditToRedo before calling Redo.

RemoveModel(IDiagramModel)

Call this method to inform this undo manager that it no longer will be notified of model Changed events.

Declaration

public virtual void RemoveModel(IDiagramModel model)

Parameters

Type	Name	Description
IDiagramModel	model

Remarks

This just removes model from the list of Models.

RollbackTransaction()

Just call EndTransaction(Boolean, String), rolling back the current transaction.

Declaration

public bool RollbackTransaction()

Returns

Type	Description
Boolean	the value of the call to EndTransaction(Boolean, String)

SkipEvent(ModelChangedEventArgs)

This predicate is responsible for deciding if a ModelChangedEventArgs is not interesting enough to be recorded.

Declaration

protected virtual bool SkipEvent(ModelChangedEventArgs evt)

Parameters

Type	Name	Description
ModelChangedEventArgs	evt

Returns

Type	Description
Boolean	normally false, which causes the given event to be remembered; but true for negative valued enumerations of ModelChange.

StartTransaction(String)

Begin a transaction, where the changes are held by a UndoManager.CompoundEdit.

Declaration

public virtual bool StartTransaction(string tname)

Parameters

Type	Name	Description
String	tname

Returns

Type	Description
Boolean	true if starting a top-level transaction

Remarks

Transactions can be nested:

Nested transactions will share the same compound edit as the top-level one. This will raise a Changed event for each of the Models, with a hint of StartedTransaction.

ToString()

For debugging.

Declaration

public override string ToString()

Returns

Type	Description
String

Undo()

Restore the state of some models to before the current IUndoableEdit.

Declaration

public virtual void Undo()

Remarks

This calls Undo() on the current EditToUndo. This will raise a Changed event with a hint of StartingUndo before actually performing the undo, and will raise a Changed event with a hint of FinishedUndo afterwards. The Data is the UndoManager.CompoundEdit that was the value of EditToUndo before calling Undo.