Published by SYBEX
£19.95
GEM is
not a system that you can learn overnight. Indeed if you are new to
programming a graphics oriented system, then you will find that
there are a large number of new concepts which you have to grasp in
order to fully understand, and thus get the best out of, GEM. The
first books published which gave information about GEM programming
were very much repeats of the Digital Research 'GEM Programmers
Guide', giving a function by function description of the facilities
of GEM. They told you, for instance, that to set the font alignment
to baseline mode, then you use such-and-such a call. What they did
not do was tell you why you would want to set the alignment at all.
This is where the SYBEX 'Programmers guide to GEM' comes in.
This book, aimed at both IBM and Atari owners (see
later), gives you a good grounding to each set of library functions,
explaining what they do, why you would want to do them, and it
usually gives a few examples of 'C' source code to experiment with.
Very good use is made of illustrations to support the text (in the
given alignment case, an example of each effect is shown).
The book has six chapters, covering: Introduction to
GEM; the Application Environment Services (AES), including an
overview and then complete function descriptions; The Virtual Device
Interface (VDI), including a short primer on graphics and then the
VDI functions; GEM SAMPLE PROGRAM: HELLO, a complete GEM
application, with listing and full explanation; GEM DEMO (DOODLE), a
more complex example (see below); ADVANCED GEM TOPICS, including
design, Metafiles, debugging, the bindings, and a tool survey. The
six appendixes include a good glossary, AES and VDI quick
references, Resource construction set tutorial, the listing of DEMO,
and Metafile functions.
While I think that the general descriptions of the
AES and VDI functions of this book make it the best yet, what really
makes it a must for the new programmer is the two sample programs.
When I first started GEM programming, all I had to learn from was a
single relatively un-commented listing (ahh!). This book provides
two complete programs (header files as well) as examples, and
thoroughly explains why each command is being done. Thus instead of
telling you that at the start of your program you should have these
seven lines, it actually explains why you should have them, and what
they are doing: By providing this sort of information you will
become a much more proficient programmer because you will understand
what you are doing. The second example used is DRI's DR DOODLE
program, and includes listings of all of the standard GEM header
files.
While
this book is very good, it does have its omissions. I cannot find
any reference to the vqmouse or vqtattributes functions, or indeed
many other 'lower level' functions. The reason for this (according
to the preface), is that they wanted to give a 'conceptual
framework' tutorial, not a reference manual. But although you will
still need a separate 'function by function' manual, the books
advantages outweigh this (I think slight) disadvantage.
In general, this book is well worth the (rather
large) asking price, and I recommed it for anyone's library.
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