Layout Managers
Author: Jeroen van der Zijp

FOX is Platform Indepence!

Goals.

Developing a single application for multiple platforms is a difficult task. The most significant issue is the need for a clean solution for developing Graphical User Interfaces [GUI's]. FOX aims to address this by providing a single GUI library that can run on different computer hardware and operating system environments. The benefits to application vendors and developers are clear:

1. Development effort to support multiple environments is substantially reduced. After development, your FOX based application is only a compile away from running on other operating systems. When multiple hardware and software combinations are required by customers operating in a heterogeneous environment, using a single GUI system such as FOX is clearly the most cost-effective method to achieve the goal.
2. Availability of your software on other platforms will engender additional revenues. Without the necessity of additional development work, the cost of which would have to be amortized over the number of sales, additional revenues can be engendered by having your software be available on multiple hardware and software environments. Software development is a costly undertaking; because of this, software vendors typically limit the number of platforms to a small subset of the platforms being used by all customers, effectively leaving certain customers in the dark. FOX allows applications to be developed on one platform, then simply recompile the application on a number of other hardware/software systems. Because the cost of doing so is negligible, this approach will be able to generate positive cashflow even with low sales volumes.
3. Captive audience. If the application you're developing is available on all platforms, you may be able to create a captive customer base on hardware/software systems where your competitor is absent; you may in fact even be able to charge premium prices. Using the additional revenues derived from these customers, your product will be able to derive a steady addional revenue stream which will allow you to compete more aggressively against your single-platform competitor.
4. Higher Quality. For programmers, the benefits of multi-platform development v.s. single platform development are the additional confidence and code quality that compiling under different environments will give. For example, I have compiled FOX on a number of different systems, and different compilers will discover different types of code bugs. By compiling on all these different systems, FOX has gotten quite a bit better in the course of time.
5. Control Your Destiny. Programmers understand it as a matter of course that they need to continually work to track the changes in a system's API's. But what if the system vendor is also your competitor? In such a case, you will loose, sooner or later. The FOX GUI Library provides a platform-independent escape hatch that relies only on core system facilities which can be expected to be present on any modern operating system.

Approach.

FOX attains the goal of platform independence by eliminating all system dependencies from its public interfaces. In fact, a typical FOX application may not even need to include any system-specific header files at all! By not including e.g. X-Windows header files, applications can not even accidentally slip up and introduce platform dependencies. This strategy is also carried out inside FOX itself. Thus, large parts of FOX are in fact defined entirely in FOX itself. The only dependencies are concentrated in a few select base classes where this couldn't be avoided.

The following salient points highlight some fundamental benefits of FOX vis-a-vis other purported platform independent toolkits:

1. Eliminate all platform specific header files. Applications should only include header files from FOX, and a few header files for such basic system services as opening files etc.
2. Internal Layering. FOX itself relies largely on FOX base classes, and therefore a large fraction of FOX itself is platform independent as well.
3. Rely only on low-level system facilities. FOX relies only on core system facilities, and does NOT wrap native GUI libraries or toolkits. This has the following benefits:

- Identical behaviour. The behaviour will be close to identical on all systems, as the behaviour is completely controlled by the FOX implementation, rather than some underlying library.
- Identical looks. FOX applications will look the same no matter what system you're running it on.
- Ability to subclass. Because FOX is written from the ground up in C++, and is NOT a C++ wrapper around some other legacy toolkit or library, FOX Controls may be subclassed and extended by application programmers. Moreover, if these additions can be done by calling upon FOX built-in facilities, those additions will be platform independent also.
- Higer Quality. It is a given in software development that those facilities which are most frequently used are the ones which are most stable. Thus, by using core system facilities instead of higher-level transient API's, the impact of the underlying system's instability is minimized. A chain is as strong as the weakest link, and while I can not control the quality of the links, I can minimize the number of them.
- Higher Speed. Eliminating layers between FOX and the underlying system not only increases the application's quality, it will also make it faster, and reduce memory overhead.
- Go to the Bedrock. FOX's core facilities needed from the target system are things like mouse/keyboard event handling, and basic graphics facilities such as drawing of lines and rectangles [and some other system facilities]. In most operating systems, these are fairly mature API's and not subject to much change. If you want to build a big building, you need to go down to the solid bedrock. This is what FOX does.

4. FOX is extensible. The FOX library is designed to be open-ended and extensible. What this means is that unlike other libraries which take the approach of wrapping legacy GUI toolkits, FOX may be extended with Custom Controls and Widgets which will set your application apart from the others. Building Custom Controls is extremely easy in FOX, as it is essentially just a matter of C++ subclassing.
5. FOX is available under Library GNU Public License. Since FOX is distributed in source form under LGPL, you have the ability to make changes or extensions to FOX to suit your needs. Having FOX inspected by 1000's of programmers all over the world will iron out any bugs it may have very quickly. This process is already under way.

I care a great deal about software quality; I imagine, so do you. In the course of my programming life, I have ran into many situations where the bugs I needed to fix were not in my own code, but in someone else's, and of course I didn't have the source. Thus, the quality of my own software was limited by the quality of someone else's. Problem is, the developers of the libraries and software I depend on are frequently not motivated to make their software correct.

This has made me a firm believer in the GPL or Open Source model of software development. FOX was started in part because I didn't want to explain to our customers that the reason X or Y didn't work was because of the broken software or libraries on their machine. The only way one can create high-quality applications is to bring as much of the underlying system under one's control as possible. Hence the Go to the Bedrock philosophy.

FOX is not perfect. But as the source code is available under LGPL, it has the advantage that its imperfections can be addressed as soon as they are discovered.

Why Windows NT?

Some people may argue that porting FOX to Windows ``helps'' Microsoft. It doesn't. Porting FOX to Windows NT does however help application vendors:- instead of subjugating to a proprietary lock-in GUI environment, they can now ship their application on a large variety of platforms, like LINUX, and this with little or no additional effort, and derive additional revenues.

In addition, being distributed under LGPL, it lowers costs, and does not incur any license fees for distribution. Being distributed under LGPL also has the concomittant benefit that a large number of people may inspect the source code, and spot its inevitable deficiencies; thus, more bugs are found and they are found more quickly. Remember, the person which is the most motivated to fix a bug is the one bitten by it; under the Open Source development model, this person can actually localize, and possibly fix the bug himself, and contribute those changes to the library.

Finally, I believe application developers will find the FOX library a more attractive alternative. For a software developer, the FOX Library is far more easy to learn, and offers some unique benefits, such as tying Widgets [Controls] together with little effort, being able to subclass from existing Widgets to make custom ones, and last but not least the ability to modify FOX's source code itself if necessary. FOX represents what I consider to be the ideal GUI Library; I wrote FOX to use it myself!

Copyright © 1997,2001 Jeroen van der Zijp, All Rights Reserved.