Exploring 32-bit Presentation Manager Under WARP

In this section we look specifically at the messaging function within Presentation Manager (PM).

Sending and receiving messages lies at the heart of how PM applications communicate with each other and the system. Messages may be sent synchronously and posted asynchronously. The mismanagement of messages by an application leads frequently to the 'Bad Application' Pop-up dialog. In extreme cases deadlocks result.

This topic applies to OS/2 V3, which introduced the 32-bit version of Presentation Manager. The previous 16-bit environment has analogous concepts which are briefly explored through a final worked example.

Pre-requisites to any PM debugging requires the following:

• Availability of the symbol file (PMMERGE.SYM) for PMMERGE.DLL. This should be installed in the same directory as PMMERGE.DLL when using the Kernel Debugger or for dump analysis, in the same directory as the Dump Formatter.

• Availability of the PM programming reference from the Programmer's ToolKit.

• Also of use, is ready access to the C header files from the Programmer's Toolkit.

We start by giving an overview of the PM messaging environment in which an application's PM thread operates.