Hi again,
Another book I read recently is Writing Your Own OSF/Motif Widgets, by Donald L. McMinds & Joseph P. Whitty of HP. McMinds is a technical author with lots of experience with documenting Motif, and Whitty is a software engineer and the developer of the XmText and XmTextField widgets.
The book is nearly 500 pages long, but the second half is just the source listings. The first half of the book takes a `cookbook' approach, first describing the widget writing process in the abstract, then describing its application for a subclass of XmPrimitive (a `Knob' widget), a subclass of XmManager (a `Grid' widget) and for a subclass of XmGadget (a `Knob' gadget).
This is a _very_ dull book, definitely a reference work rather than something you would read straight through for interest. The widget writing process involves creation and modification of many data structures, in effect implementing a subclass using an object-oriented mechanism written in C. Each step is explained clearly, but nothing could make this interesting.
I have to admit that I haven't had time to try out the process described in this book, so I can't say for sure how well this book succeeds in its purpose. It's clear from the book that the Motif widget writing process is very complicated, and if you need to know all this stuff, then the book could save you months of study. Having read this book, there's no way I'd try writing a Motif widget without it.
David
David Price, TMS-OS