Object Linking and Embedding (OLE)

Object Linking and Embedding (OLE):

OLE is technology developed by Microsoft that allows embedding and linking to documents and other objects. It links as well as embeds some elements from other application.

For ex: We can embed a spread sheet from excel in the word document. We can get picture from MS paint in the MS word.

OLE Drag and Drop:

OLE means transfer of data from source to destination hence for OLE drag and drop operations

 There are three things that are required –

1.     An Interface IDropSource.

2.     An Interface IDropTarget.

3.     Some library code that manage the drag and drop process.

·        Drag and Drop operation is similar to copy and paste operation.

·        The Drag and Drop is performed between two applications or between an application and the window.

·        When user start the drag, cursor change and turn into the “+” sign. If we are dropping some object on the target then the object gets copied on the target.

·        Source Side: There is a key function executed in drag and drop process that is DoDragDrop(). The task of this function is to create an object of class ColeDropSource. The DoDragDrop() function is a looping function which does not return anything for some time. It returns only when user performs the drop operation or user cancels the operation or when some period of time is completed. The DoDragDrop() function is called when user click the mouse inside the tracking rectangle.

·        Destination Side: At this side, the dragged object must be dropped on some target. There is a target class named ColeDropTarget which implements IDropTarget interface. This interface holds the IDropSource pointer which finally link to ColeDropSource object.