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Drag and Drop

alphabetized list), that view’s ordering takes precedence over the selection order. If both the source and destination provide a spatial ordering (such as in graphic applications), the spatial ordering takes precedence over the selection order.

Automatic Scrolling

When an item is being dragged, your application must determine whether to scroll the contents or allow the item to “escape” the window. If your application allows items to be dragged outside of windows, you should define an autoscrolling region. Automatically scroll a destination window only if it is also the source window and is frontmost. Don’t autoscroll inactive windows.

Using the Trash as a Destination

The Drag Manager makes the Trash available to applications.

Dragging items to the Trash results in moving the item from the source to the Trash. For example, dragging a text selection from a word-processing application and dropping it on the Trash icon (or in the Trash window) results in the text being deleted from the application and a clipping containing that text being created inside the Trash. Note that the item is moved, although it is dragged between two containers. This exception to the rules described earlier is appropriate because the user can undo the operation by dragging the clipping out of the Trash back to its original source; it is consistent with the principle of preventing accidental data loss.

It is important to preserve the Trash’s container property; do not simply delete the source without creating a clipping or other item in the Trash.

Drop Feedback

When the user releases the mouse button after dragging an item to a destination, feedback should inform the user that the drag-and-drop operation was successful. While this feedback can be visual, it is primarily behavioral in nature. The behavior comes from the semantic operation indicated by the drag-and-drop sequence. Examples of this behavior are given below.

Apple Computer, Inc. June 2002

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Drag and Drop

Finder Icons

When the user moves an item by dropping its icon on a folder icon, the dropped icon disappears and the highlighting is removed from the destination folder icon.

If an icon represents a task, such as printing, you may want to provide progress feedback to indicate that the task is being carried out.

Graphics

When dropping graphics, the drop feedback is usually the movement of the actual item to the location of the mouse-up event.

Text

After text is dropped, it is shown highlighted at its destination.

When text is dropped in a destination that supports styled text, the dropped text should maintain its font, typeface, and size attributes. If the destination does not support styled text, the dropped text should assume the font, typeface, and size attributes specified by the destination insertion point.

Drag-and-drop operations involving text should support intelligent cut-and-paste rules, as explained in “Intelligent Cut and Paste” (page 194).

Transferring a Selection

After a successful drag-and-drop sequence involving a single window, the selection feedback is maintained at the new location. This behavior provides an important user cue and allows the user to reposition the selection without having to make the selection again.

If the user drags an item from an active window to an inactive window, the dragged item becomes a background selection at the destination; the selection in the active window remains selected. This guideline also applies in the reverse situation, where an item is dragged from an inactive window to an active window.

226Drop Feedback

Apple Computer, Inc. June 2002