9763b5530d
git-svn-id: svn://svn.compuextreme.de/Viitor/V961/Viitor_cc65@4236 504e572c-2e33-0410-9681-be2bf7408885
82 lines
4.5 KiB
HTML
82 lines
4.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.20">
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<TITLE>GEOSLib docs: What have you got and what to do with it?</TITLE>
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<LINK HREF="geos-3.html" REL=next>
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<LINK HREF="geos-1.html" REL=previous>
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<LINK HREF="geos.html#toc2" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="geos-3.html">Next</A>
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<A HREF="geos-1.html">Previous</A>
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<A HREF="geos.html#toc2">Contents</A>
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<HR>
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<H2><A NAME="s2">2.</A> <A HREF="geos.html#toc2">What have you got and what to do with it?</A></H2>
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<P>This chapter describes some rules you ought to obey, and how to use GEOSLib.</P>
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<H2><A NAME="ss2.1">2.1</A> <A HREF="geos.html#toc2.1">Usage</A>
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</H2>
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<P>Apart from this file, which merely describes only standard GEOS library functions, you should read
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<CODE>grc</CODE> (GEOS resource compiler) documentation. There are informations about necessary resource
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files (each GEOS application needs at least one) and the building process - what should be done
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and in what order. Please also read cc65's documentation on how to compile C, assembler and link
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everything together.</P>
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<P>All in all, you just need to place
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<BLOCKQUOTE><CODE>
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<PRE>
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#include <geos.h>
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</PRE>
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</CODE></BLOCKQUOTE>
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on top of your source.</P>
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<P>As a general rule read the sources of example programs and read the headers. These are the most
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reliable sources of knowledge ;). You will also find there many C macros representing various
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arguments passed to functions. Please use them. You will find your sources easier to understand,
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and it will be easier to find bugs.</P>
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<P>All types used in GEOSLib are <CODE>unsigned</CODE>.</P>
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<P>Screen coordinates are given in pixels unless stated differently.</P>
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<H2><A NAME="ss2.2">2.2</A> <A HREF="geos.html#toc2.2">Notes on style</A>
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</H2>
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<P>Contrary to typical GEOS assembly program which has a main function called after loading that
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setups the screen, menus, icons etc. exiting from <CODE>main</CODE> function in C is equivalent to
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calling <CODE>exit()</CODE>. These two are the only safe methods of terminating applications. DO NOT
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USE <CODE>EnterDeskTop</CODE>! Your data may be lost as library destructors and functions registered
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with <CODE>atexit</CODE> will not be called.</P>
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<P>For GEOS GUI applications the recommended program structure is to have everything initialized
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in <CODE>main</CODE> function and at the end of it a call to <CODE>MainLoop()</CODE> function. WARNING! This
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function never returns, any code between <CODE>MainLoop();</CODE> and the end of <CODE>main</CODE> will not
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be executed. You have to call <CODE>exit()</CODE> explicitly somewhere in your code (e.g. in a menu
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handler or via DialogBox action).</P>
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<P>Whenever possible use definitions from <CODE>gsym.h</CODE>. The resulting code is translated by cc65 into
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series of <CODE>lda</CODE> and <CODE>sta</CODE>, so you can't do it better :-).</P>
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<P>Don't hesitate to use library functions. Everything was written with size and speed in mind. In
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fact many calls are just redirections to GEOS kernal which results in simple <CODE>jsr</CODE>.</P>
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<P>The <CODE>main</CODE> function receives the standard <CODE>argc</CODE> and <CODE>argv</CODE> parameters. There are
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always either 1 or 3 parameters. DOS application name is always set as <CODE>argv[0]</CODE>.
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If present, <CODE>argv[1]</CODE> and <CODE>argv[2]</CODE> will be set to data filename and data diskname (it only
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works if user double-clicks on data file associated with your application). Note that it is up
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to your application to determine which of the available (up to four) disk drives has the disk
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with given diskname inside. If this fails your program should ask to insert the proper disk into
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one of available drives.</P>
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<P>You might wonder why I have chosen sometimes weird order of arguments in functions. I just
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wanted to avoid unnecessary pushing and popping arguments from stack because cc65 can pass single
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<CODE>unsigned int</CODE> through CPU registers.</P>
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<P>Do not try to compile in strict ANSI mode. Library uses cc65 extensions which are not available in
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ANSI.</P>
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<P>It is possible to use dynamically loaded modules, three such modules are provided:
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GEOS TGI driver, GEOS EMD driver (for VDC extended memory) and GEOS JOY driver.
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Just make sure that their filenames appear UPPERCASE in DeskTop. There are no more special
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recommendations, read cc65 documentation about modules and demo programs source code.</P>
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<HR>
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<A HREF="geos-3.html">Next</A>
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<A HREF="geos-1.html">Previous</A>
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<A HREF="geos.html#toc2">Contents</A>
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</BODY>
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</HTML>
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