The source is responsible for starting a direct manipulation operation. Startup can be accomplished only with a pointing device, such as a mouse. The operation starts when the application detects that a drag button has been pressed and the pointing device has moved. Dragging continues until terminated, which is usually when the button is released.

Although the direct manipulation protocol lets the application use any button for dragging, it is recommended that the system-defined drag button be used for direct manipulation operations.

The source has the following responsibilities in preparing for the actual drag of the objects across the screen:

• Allocate and initialize the DRAGINFO data structure that conveys the necessary information about each object to the target.

• Initialize a set of DRAGIMAGE data structures that describe the image to be displayed during the drag operation.

• Make the following information known to the system:

  • The type of each object being directly manipulated

  • The rendering mechanism and format for each object

  • The suggested name of the object at the target

  • The name of the container or folder containing the source object

  • The name of the object at the source

  • The true type of each object being directly manipulated

  • The native rendering mechanism and format for each object

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