Direct manipulation of icons on the Presentation Manager desktop in order to carry out processing tasks has been possible since the first release of Presentation Manager in OS/2 Version 1.1, but only in Version 1.3 was a standard method introduced for implementing such function. Previously, each programmer needed to devise a set of protocols, and write code in every application to handle all the mouse messages and interaction between windows that may have been needed.
OS/2 Version 1.3 introduced some standards for coding direct manipulation operations, in the form of new message classes (the DM_xxxx messages), and standard protocols known as rendering mechanisms, which are used to communicate required information for commonly used direct manipulation operations. This support is continued in OS/2 V2.0, and is of increased importance since the Workplace Shell itself makes extensive use of direct manipulation. Applications that use direct manipulation are therefore more likely to be written under Version 2.0, either to interact with one another or to make use of Workplace Shell facilities such as printer objects or the shredder.
This chapter discusses the use of direct manipulation in a program, covering the major messages and data structures involved, and the use of the standard rendering mechanisms. Examples of the use of these messages and data structures are given, along with guidance on implementing a private rendering mechanism to meet the needs of a particular application.