Developing cross platform program/game from ground up - part 4

Cross Platform development by standardization.

If your going to make program work on different operating systems, you need a lot of know how about etch of operating systems, in order to support all operating systems.

The alternative is using cross platform development libraries.

First of all I'm going to talk about SDL and Allegro this two provides every thing you need to make games, the idea is that you have standard commands you can use to make sure that your game works on all operating systems they are ported to.

SDL

* Support Graphics 2D and 3D

* Handel display window/full screen window

* There events for Mouse/Keyboard/Joystick/ Multi-touch.

* Audio 8bit and 16bit.

* Filesystem

* Threads

* Supports big and little endian cpu's

Allegro

* Support Graphics 2D and 3D

* Handel display window/full screen window

* There events for Mouse/Keyboard/Joystick/ Multi-touch.

* Audio 8bit and 16bit.

* Filesystem

* Threads

* Supports big and little endian cpu's

So they are similar and provided what you need to make a games, some even make programs in this but, that's not a good idea, there are better cross platform libraries for programs.

	Linux/BSD	Windows	AROS	AmigaOS4	MorphOS	MacOSX	Haiku/BeOS	Score
Allegro	yes	yes	no	yes	yes	yes	yes	6
SDL	yes	yes	yes	yes	yes	yes	yes	7
Svgalib	yes	no	no	yes Wrapper for Picasso96	no	no	no	1 (2)
Picasso96	no	no	yes	yes	yes	no	no	3
Cybergrephics	no	no	yes	yes	yes	no	no	3
Haxe	yes	yes	no	no	no	yes	no	3

The Svgalib port for AmigaOS4, was done by me, it might need some work, its not well designed, but there are NOT many games or programs that use this library, if you look at the table you see that SDL is most supported, Allegro is not so well supported.

Some information Allegro 5 and Allegro 4 are not 100% compatible, and only Allegro 4 is officially supported by AmigaOS 4, I have not looked at Allegro 4 so I can't say accurately what the difference are, anyway I have been working a bit on Allegro 5 but not a complete port, I have only implemented what was needed for a Game, so its not even based on Allegro 5 source code, so don't expect a full Allegro 5 port from me for AmigaOS 4. Developer using the nick "Hitman", ported Allegro 4 to AmigaOS 4.

As I understand it Cybergrephics is the native graphic library for MorphOS and it was addition to Graphic.library on AmigaOS3.1,  when installing a True color graphic card in your Amiga, Picasso96 is also a graphic library to enable true colors for AmigaOS3.1 / Commodore Amiga computers, on AmigaOS4.x  Picasso96 is slowly becoming obsolete if your going to make new program or game. How this implemented in AROS I do not know all I know is that its supposed to be supported.

Here are some GUI systems QT, GTK, MUI (Magic User Interface), Reaction, that we compare to see what supports the most, I have selected a few well known operating systems.
(I have excluded mobile platforms etc, or else table gets to big.)

	Linux/BSD	Windows	AROS	AmigaOS4	MorphOS	MacOSX	Haiku/BeOS	Score
QT	yes	yes	no	yes	no	yes	yes	5
MUI	no	no	yes (clone Zune)	yes	yes	no	no	2 (or 3)
Reaction	no	no	no	yes	no	no	no	1
GTK	yes	yes	yes (Zune wrapper)	no	no	yes	yes	5
Windows Forms	yes (mono)	yes	no	no	no	yes (mono)	no	1 (or 3)
wxWidgets	yes	yes	no	no	no	yes	no	3
AGAR	yes	yes	no	no	no	yes	yes	4

Best score is 7 in this table, but no GUI system support all 7, so in other words GUI's are the tricky part when creating a cross platform application, the best GUI's to support is GTK and QT, then depending on what OS you wont to support and programming language you use MUI (Magic User Interface) or Windows Forms.

While no GUI support all the 7, the build system is what solve the problem, this how you can have different GUI's for different operating systems, you really only need to support two MUI & QT or GTK & MUI and all 7 operating systems are supported.

Different Linux distributions are not listed here because they are just repackaged Libs and programs, with different install process and package managements, I know some might disagree but lets keep this about cross platform development and not about what brand you put on your Linux distribution.

Anyway GUI and how things works is what makes operating systems unique to the users, if all operating systems behave the same there is not point having a option to choose is there?

Developing cross platform program/game from ground up - part 3

Ok, now I'm going explain a bit more about Makesfiles, and also try to condense this makefile.os4 and makefile.os3 and makefile.linux into one file.

Forst of all now we description how to build 4 different .o files, but we are using gcc to generate this files in the same way.

obj/display.o:
          gcc os3/display.c -o obj/display.o -c

obj/filesystem.o:
          gcc os3/filesystem.c -o obj/filesystem.o -c

obj/joystick.o:
          gcc os3/joystick.c -o obj/joystick.o -c

obj/audio.o:
          gcc os3/audio.c -o obj/audio.o -c

however this can be written as.

obj/%.o: $(os)/%.c
          gcc $< -o $@ -c

I know this looks cryptic but what it does is when compiler is looking for obj/filesystem.o it will use label obj/%.o as it matches the filename, $(os)/%.c means that linux/filesystem.c is needed by obj/filesystem.o.

The next line gcc $< -o $@ -c work like this.

$< is replaced by whats after the label so its going to be $(os)/%.c and this translated into linux/filesystem.c

$@ is synonym with the name to compile.

So if this is the filesystem that is compiled it will be interpreted by the compiler as:.

gcc linux/filesystem.c -o obj/filesystem.o -c

so this two lines do the same as the 8 line in the first example.

And also you can easily change build target to OS4 or OS3 or Linux or what ever you like.

By setting os=linux or os=os4 or os=os3, simple do you agree?

Developing cross platform program/game from ground up - part 2.

Understand how build process talked about in part 1 work.

So now you type make all -f makefile.os4 you get the game.exe file for AmigaOS4.

The game.exe will contain the following files for AmigaOS4:

main.cpp 
os4/display.c 
os4/filesystem.c
os4/joystick.c
os4/audio.c

The game.exe will contain the following files for AmigaOS3:

main.cpp 
os3/display.c 
os3/filesystem.c
os3/joystick.c
os3/audio.c

The game.exe will contain the following files for Linux:

main.cpp 
linux/display.c 
linux /filesystem.c
linux /joystick.c
linux /audio.c

Etch of the files in the OS folder will contain OS specific code, for example in linux/audio.c file OSS Open Sound System is used. In the os3/audio.c code for Paula audio is used. In the os4/audio.c file the AHI sound system is used.

In the os4/filesystem.c the newest DOS.Library functions are used with full support for 64BIT offsets.

In the OS3/filesystem.c the old 32bit DOS.Library functions are used, with file limit of 2GB.

In the Linux/filesystem.c the stdio C++ lib commands are used, with full 64BIT support if compile target supports it.

So what we have done is separate the OS depended parts and we are using the best possible API that we can use for etch OS target.

This is also the case for windows target, but as it use different build system, you only need to make the folder and add the file to the project in Virtual Studio.

Developing cross platform program/game from ground up - part 1.

First of all its good to know what the differences are between the operating systems.

Do some resource and see what libs are ported and what are not ported to etch operating systems you like to support.

For AmigaOS4.1 you can check http://OS4Depot.net

For AmigaOS3.1 you can check http://Aminet.

For AROS you can check http://archives.aros-exec.org/.

Often you can to etch library and check how to configure and set it up in your development enviroment.

For example if you go to libpng web page and look you see how to configure it for windows.

http://gnuwin32.sourceforge.net/packages/libpng.htm

Note for windows visual studio uses different build system then AmigaOS/Linux/AROS/MorphsOS or what ever, so I think might be best to create the project there and copy the files to the other computers.

You should have repository to track your changes and other people changes.

You can sign up a repository at code.google.com for free.

Design your application so its easy to update your program with out messing up your code.

Try to keep the OS depended code out of your game AI and general code.

If you need to draw a line make function or macro like:

app_draw_line()

this way draw line is abstracted from the OS, and it becomes easier to keep every thing compatible.

create folder in project root directory called.

linux, os3, os4, windows, osx and so on.

you will also need a folder called inc or include, here you put .h files that declare how functions will look like.

in the inc/display.h file you should have line like:

extern void app_draw_line();

extern means that app_draw_line does not need to be in the .c/.cpp file its included in, but can be in a different .c/.cpp file, this is to make sure the compiler does not get confused, because you can only have one app_draw_line function.

Setting up the makefiles.

For AmigaOS4, you make file named it Makefile.os4

          the following line should be like:

all: obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o

          gcc main.cpp obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o -o game.exe

display.o:

          gcc os4/display.c -o obj/display.o -c

filesystem.o:

          gcc os4/filesystem.c -o obj/filesystem .o -c

joystick.o:

          gcc os4/joystick.c -o obj/joystick .o -c

audio.o:

          gcc os4/audio.c -o obj/audio .o -c

create a make file for AmigaOS3 and name it Makefile.os3.

all: obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o

          gcc main.cpp obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o -o game.exe

obj/display.o:

          gcc os3/display.c -o obj/display.o -c

obj/filesystem.o:

          gcc os3/filesystem.c -o obj/filesystem .o -c

obj/joystick.o:

          gcc os3/joystick.c -o obj/joystick .o -c

obj/audio.o:

          gcc os3/audio.c -o obj/audio .o -c

create a make file for Linux and name it Makefile.linux

all: obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o

          gcc main.cpp obj/display.o obj/filesystem.o obj/joystick.o obj/audio.o -o game.exe

obj/display.o:

          gcc linux/display.c -o obj/display.o -c

obj/filesystem.o:

          gcc linux/filesystem.c -o obj/filesystem .o -c

obj/joystick.o:

          gcc linux/joystick.c -o obj/joystick .o -c

obj/audio.o:

          gcc linux/audio.c -o obj/audio .o -c

So now you see that etch target platform has its own folder, with platform dependent code, while main.cpp is on the project root folder. This is because main.cpp is shared between the different target operating systems, and should not contain any OS dependent code.

Additional support libraries most also be statically linked or dynamically linked. Its up to you how you solve that.

Note I'm not using configure scripts, well this because different operating systems do not share the same shell commands, while there is some thing called ABC shell for AmigaOS that mimics the SH shell, it does not guaranty compatibility, with 1000 of GNU commands in Linux. This simply does not work for AmigaOS.

When compiling you simply do:

make all -f makefile.os4

make all -f makefile.os3

make all -f makefile.linux

make all -f makefile.aros

you can also make soft like to from makefile.os to makefile so you can just type

make all

Prof of concept, EPL labels on AmigaOS.

Well I felt like writing something about some working I have been doing lately.

For now I'm not going to say anything about MPlayer, all I can say is that there has been some improvements.

You might have seen my Barcode application on AmigaWorld.net, well I was nostalgic about EPL & ZPL printers, but don't have a printer my self so need a application to display labels, I know there are label design tools for PC, but what is the fun in using some thing some one else has created? Besides I was also wondering about how to generate bar-codes, I often created reports for PSI and Consafe logistics, but this was not my primary role, so I did not have time to find out how to generate bar-codes, at time I did some googling and found only barcode fonts, well they are nice in word document’s and so on, but then you need to generate a word document or excel file, its a lot easier to generate CSV files and Pictures, and its pity easy to lay out rapports in HTML.

If I did have more time to play with it back then might have done some thing, but as I was saying, I did not. as it happens now I did have the time for it, first ting I did was Google and found out how to generate code39 and then I Googled and found out how to generate code128.

Barcode39 is only numbers and uppercase alphabet.
Barcode128 is upper/lower alphabet, and also the ability to compress numbers.

 I also found some information about bar-code 2 of 5, this Barcode only supports number from 0 to 9, and also as the name imply 2 are wide and 3 as narrow lines

I know this is geeky stuff, but some times geeky stuff is useful

Almost all postal and logistic company's tag packages so they can easy lookup who the package belongs to and where it is. Also at the cash register at the local grocery store, use barcode to register what they sell. At service department in PSI and Consafe Logistics (Capbit/Captura) they used bar code to track service on defect products that has been sent for repair.

So every company small or large company's use barcodes in one way or the other.

And this is way this is interesting, if you thinking about starting your own company or if you work for some company I'm sure your in contact with barcodes.

Only basic EPL commands are supported, but program can easily to be extended to support more commands, this is just a prof of concept.

And also while I can generate the label I can't print it, find desktop printers that work with AmigaOS tricky.

If you like to buy a Label printer and use it on AmigaOS, I can inform you that they should work, as long you use ZPL or EPL program language.

You can also find documents for EPSON label printers, but they are more tricky, you see they use ESC codes, and HEX values so not so easy.

Datamax Compact 4 I don't know anything intersecting about it sorry, I know they are good quality but do not know any thing about language they support.

Some of the Intermec printers supports the EPL language this I know.