Platform-integrated drag and drop

Common Widgets provides platform-integrated drag and drop capabilities to VA Smalltalk applications. Common Widgets drag and drop gives applications access to the native drag and drop systems of each platform, and minimizes the need to write platform-specific code. Common Widgets drag and drop is based on the OSF/Motif R1.2 drag and drop model.

Platform-integrated drag and drop involves two sides: the source and the destination. The source and destination can be the same application or different applications. For example, a user can drag from a widget that is part of application A and drop on that same widget, on another widget in application A, or on a widget in application B.

When a user performs a valid drop, data is transferred from the source to the destination. In Common Widgets drag and drop, data transfer can be done at several levels of complexity. The levels of data transfer include the following, beginning with the simplest:

•	Data transfer using built-in types. For example, String data can be transferred using 'STRING' and CgPixmap data can be transferred using 'PIXMAP.'

•	ByteArray data transfer. This is the default.

•	Custom data transfer, which enables you to add to the set of built-in types.

To complete the first two levels of data transfer, you do not need to write platform-specific code. These types of data transfer are described in this section. To complete a custom data transfer you must extend Common Widgets drag and drop by writing custom converters, which is not covered in this manual.