Introduction to PM Programming - Feb 1996

Introduction

The purpose of this column is to provide the readers out there who are not familiar with PM application development the information necessary to satisfy their curiosity, educate themselves, and give them an advantage over the documentation supplied by IBM. Of course, much of this stuff could probably be found in one of the many books out there, but the problem with books in general is that they don't answer the questions you have after you read the book the first time through.

I will gladly entertain feedback from the readers about what was "glossed over" or what was detailed well, what tangential topics need to be covered and what superfluous crap should have been removed. This feedback is essential in guaranteeing that you get what you pay for. [grin]

It should be said that you must not depend solely on this column to teach you how to develop PM applications; instead, this should be viewed as a supplement to your other information storehouses (books, the network conferences, etc.). Because this column must take a general approach, there will be some topics that you would like to see discussed that really do not belong here. Specific questions can be directed to me via email and I will do my best to answer them in a timely fashion.

This Month

The results are in! You want more "meat" with your potatoes. Heck, I could have figured that out, since anyone can read an online reference to find out what a particular message does. Anyway, we will look at the slider control, how it is used, and dissect a sample application which uses three sliders to display a fillet.

==What Is a Slider, Anyway?

Back in the days when OS/2 1.2 was around, a lot of people found that they were using the scroll bars to display various types of things. However, when these uses were viewed collectively, it was noticed that the things that were being done had similar characteristics:

Most had feedback to display a number corresponding to the scrollbar position - whether it was the size of an object, the length of time to process a calculation, or something else, the user had to know what they were selecting.
Most used the number from the scrollbar to control some aspect of the application - I keep thinking about the myriad of applications that allowed to you to define a color. All would display three scroll bars which controlled the red, green, and blue components of the color being defined and this color was updated as you moved the scroll bars.

When combined with other, commonly-seen user interface components, e.g. progress indicators, it was decided that these applications would be better served by a window class that was tailored somewhat for these types of things. Thus, the slider was born. (The circular slider made its debut in 2.0 and the programming interface in 2.1.)

The slider (shown below) has many components: