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In This Article

Drag and Drop

SyntaxEditor supports drag and drop operations within itself, as well as with external controls.

Tip

Drag and Drop and Clipboard operations share many of the same concepts. Refer to the Clipboard Operations topic for details specific to working with the clipboard.

Allowing Drag and Drop

SyntaxEditor supports drag and drop by default. However, drags and drops can also be disabled if desired.

The SyntaxEditor.AllowDrag property can be set to false to disable dragging from the editor.

The SyntaxEditor.AllowDrop property can be set to false to disable dropping onto the editor.

Dragging with HTML and RTF Export

The text that is dragged can include HTML and RTF exported highlighting. Then, if you drop the text in an application such as Word, the text will appear with syntax highlighting.

The SyntaxEditor.CanCutCopyDragWithHtml property controls whether HTML exporting is performed whenever dragging.

The SyntaxEditor.CanCutCopyDragWithRtf property controls whether RTF exporting is performed whenever dragging.

Customizing Text to be Dragged

Sometimes it is useful to be able to customize the text, or objects, to be dragged. The SyntaxEditor.CutCopyDrag event is raised before text is cut/copied to the clipboard and also before a drag occurs (see the Clipboard Operations topic for additional details).

In its event arguments, it passes the IDataStore that is to be dragged as well as the type of operation that will be performed. When the event is raised, the IDataStore has already been initialized with DataFormats.UnicodeText and DataFormats.Text entries based on the current selection in the editor. The IDataStore can be modified to customize what is dragged.

Note

The IDataStore interface is used instead of IDataObject. IDataStore is designed to use many of the same method signatures that IDataObject does and provides a consistent API across our supported platforms.

Customizing Text to be Dropped

Just like the SyntaxEditor.CutCopyDrag event, an event is provided to allow for customization of text that is to be pasted or dropped onto the editor (see the Clipboard Operations topic for additional details). The PasteDragDrop event is raised in several situations:

  • Paste operations
  • Paste completion
  • CanPaste checks
  • Drag enter
  • Drag over
  • Drag/drop

This event passes the IDataStore that is to be dropped and the source of the event. The IDataStore is similar to IDataObject (see note above) and provides access to any shared application data (such as non-text formats) that was used to trigger the event.

The PasteDragDropEventArgs.Text property can be set to the text to be inserted. It also can be set to null to insert nothing.

The Text property is auto-populated by examining the IDataStore for the following standard text formats (in this order):

  • DataFormats.UnicodeText
  • DataFormats.Text
  • DataFormats.StringFormat

If dragged data doesn't include one of the standard text formats, then the Text property will be null. The easiest way to support dragging onto SyntaxEditor is to ensure that one of the standard text formats is set when initiating the drag.

The following code demonstrates initiating a drag with a String value that will be automatically converted to DataFormats.StringFormat.

using System.Windows;
...
DragDrop.DoDragDrop(dragSource, "Insert Drag Text Here", DragDropEffects.Copy);

If more than one data format is needed, simply make sure text is one of the standard formats like shown in the following code:

using System.Windows;
...
var dataObject = new DataObject();
dataObject.SetData(myCustomObject);
dataObject.SetText("Insert Drag Text Here");
DragDrop.DoDragDrop(dragSource, dataObject, DragDropEffects.Copy);

See the "Customizing Drag Behavior" section below for more advanced drag scenarios like file drop.

Important

For drag-related actions, the PasteDragDropEventArgs.DragEventArgs operation must be set to Copy or Move to indicate that the object can be dropped.

The PasteDragDropEventArgs.Text property's actual value only has to be assigned for the DragDrop action.

Tip

The PasteDragDropAction.DragOver action can typically be ignored unless you wish to change the drag effect based on the position of the pointer or need to support custom drag objects.

Customizing Drag Operations

The PasteDragDropEventArgs.DragEventArgs property is used to access the arguments that caused a drag-related event. SyntaxEditor will use the DragEventArgs.Effects property to determine the type of drag operation, if any, that should be accepted. Under default scenarios, this property is initialized based on the availability of text on the IDataStore, the read-only state of the drag and/or drop locations, and the position of the pointer within the IEditorView. To change the default behavior, the value of the DragEventArgs.Effects property must be changed to the desired operation.

Operation Description
DragDropEffects.Copy Indicates drag should be allowed that is a copy of the source.
DragDropEffects.Move Indicates drag should be allowed that will move the text from the source to the drop location.
DragDropEffects.None Indicates drag should not be allowed.

Multiple drag-related actions are handled by the PasteDragDrop event and are raised in the following order:

  • DragEnter
  • DragOver
  • DragDrop

The current action can be determined by the PasteDragDropEventArgs.Action property.

DragEnter Action

The PasteDragDropAction.DragEnter action occurs when a drag operation first moves over the IEditorView, and the result of this action will determine if subsequent actions are raised.

The value of DragEventArgs.Effects must be set to Copy or Move to allow a drop; otherwise, None if drop is not allowed.

Tip

Setting a non-default operation for this event is only necessary if the data being dragged is not automatically recognized as text or to support dropping custom data onto the view.

Important

The DragOver and DragDrop actions will not be raised if the DragEnter action is completed with the operation set to None.

DragOver Action

The PasteDragDropAction.DragOver action occurs immediately after a drag operation moves over the IEditorView and will continue to be raised every time the pointer moves while it is still over the IEditorView.

The value of DragEventArgs.Effects must be set to Copy or Move to allow a drop at the current pointer location; otherwise, None if drop is not allowed.

Tip

The DragOver action will typically assign the same operation as the DragEnter action unless special handling is necessary based on the position of the pointer. Refer to the Hit Testing topic for additional details about determine the relevant position of the pointer.

Important

If custom logic was used to override the default operation of the DragEnter action, the same logic will typically need to be repeated for the DragOver action.

DragDrop Action

The PasteDragDropAction.DragDrop action occurs when an allowed drag operation is completed.

The value of DragEventArgs.Effects can be set to Copy or Move to allow for a default text-based drag to be completed. When set to Copy or Move, the value of the PasteDragDropEventArgs.Text property will determine the text that is dropped onto the view. If the Text property is null, a Copy or Move operation will have no effect. Set the operation to None to prevent any default handling of text-based drag operations.

Important

If custom logic is used to handle the drop action, the operation must be set to None to prevent any default handling of text-based data that may have also been available with the drag event. Even when custom data is expected, a fallback text-based format of the data may have also been present which would be dropped onto the view if not canceled.

File Drop Example

Dragging a file from the file system and onto the editor (i.e., DataFormats.FileDrop) is a good example of a scenario which requires customizing the drag operations.

The following code illustrates checking for file drop and configuring the editor to allow the drag:

using System.Windows;
using ActiproSoftware.Windows.Controls.SyntaxEditor;
...
private void OnEditorPasteDragDrop(object sender, PasteDragDropEventArgs e) {
	if (e.DataStore.GetDataPresent(DataFormats.FileDrop)) {
		switch (e.Action) {
			case PasteDragDropAction.DragEnter:
			case PasteDragDropAction.DragOver:
				// Allow drag
				e.DragEventArgs.Effects = DragDropEffects.Copy;
			case PasteDragDropAction.DragDrop:
				// Cancel default handling
				e.DragEventArgs.Effects = DragDropEffects.None;
				// Process the dropped file here
		}
	}
}

Reselection of Text After a Drop

By default, any dropped text will be reselected following the drop. The SyntaxEditor.IsDragDropTextReselectEnabled property can be set to false to disable this behavior.