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AtariST developers: Question and Answer Bulletin - February 1986
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Question and Answer Bulletin February 1986
Copyright (C) 1986 by Atari Corp. "all rights reserved"
1196 Borregas Ave., Sunnyvale, Ca. 94086
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Here are the latest questions from the Atari developers
mailbag as answered by John Feagans, Director of Software
Technology. Leave questions on Compuserve for PIN 70007,1072
or GO PCS57 for Atari developer SIG information.
Q How can I have a different background color for text. There
does not seem to be anything I can set to make this happen.
A A way we recommend to make this happen is to do a rectangle
fill of the area behind the text then use v_gtext with a
transparent writing mode.
Q I have a GEM application that I am porting from the IBM PC.
Everything compiles O.K. but I get a number of undefined
symbols in the link step. Some of these symbols are
dos_free, dos_gdrive, dos_lseek, and dos_open.
A The problem here is some differences in name between what you
are using, what is described in the GEMDOS spec, and what is
actually in the bindings. Here is a table which may explain
what is happening:
---------------------------------------------
|Your code GEM DOS manual osbind.h|
|-------------------------------------------|
|dos_free d_free Dfree |
|dos_gdrive d_getdrv Dgetdrv |
|dos_lseek f_seek Fseek |
|dos_open d_open Fopen |
---------------------------------------------
Q From the VDI there doesn't seem to be a call to set pixels.
How do I do it and be compatible with all resolutions?
A You can do it by drawing a 1 pixel wide line with a length of
1 pixel. There is also a line-A call for setting pixels.
The latter method is much faster, however, it does not clip.
Q I just installed my ROMs and the system doesn't come up. It
is just a white screen. It is like this every time I reset.
Oh...there it is...what happened?
A If you have just installed your ROMs and do not have a disk
drive attached, the TOS is going to spend considerable time
attempting to read some files from disk. It is looking for
desk accessories, an auto folder which may contain drivers to
load, and a desktop.inf file created if you saved a desktop.
If you want to shorten the power-up process, then have a disk
attached with a valid floppy disk in the drive.
Q I just ported my IBM PC version and have the symbol UMULDIV
undefined.
A There is a problem with vdibind. The binding defines
MUL_DIV, mul_div, and umul_div, but the symbol UMUL_DIV is
missing. If you are programming in C perhaps you could
#define it in a header file. In assembler, you could equate
UMUL_DIV to umul_div.
Q Can I boot another operating system if I have TOS in ROM?
A Yes. The system has been designed so that a disk with a boot
sector can have another operating system which can be loaded
in. Another way to load another system would be to put a
driver in the auto folder on the system disk. A third
interesting method would be to make a desk accessory which
loads the new system. It is also possible for a program to
perform an extended bios call PUNTAES which frees up the
memory used by the AES and desktop while preserving the
bios,dos, and VDI.
Q How can I load in code from BASIC? Where is it put? How do
I allocate space for it?
A To use the BLOAD function you must first allocate a string
array big enough to hold your code. Next use the varptr
function to get the address of the storage area. Use BLOAD
with this address and the CALL function to execute your code.
One final point--make sure the code is relocatable and
completely relative as BLOAD does no fix-ups.
Q How are the icon outlines dragged on the desktop and what is
the shape?
A Icons are dragged on the desktop by moving a polyline XOR
box. The vertices correspond to the edges of the mask data
for the icon.
Q How do I stop BASIC from drawing windows on my output
screen?
A Windows are redrawn when BASIC calls a routine in the event
library. Some examples of these routines are evnt_multi,
evnt_keyboard and evnt_button. It is possible to stop the
evnt_multi calls because there is a BASIC system table called
SYSTAB. Check the documentation for particulars. At an
offset of +24 there is a variable called GEMFLAG. A POKE of
1 in this location turns the event calls off and a POKE 0
turns the event calls on.
Q When I double click on AS68 from the desktop, the screen
turns white and immediately returns to the desktop. How do I
type in the name of the file to assemble?
A It is possible to run AS68 from the desktop. The procedure is
to install it as a TTP type, (TOS takes parameters) and save
desktop, or show-info and rename it as a .TTP. Next time you
double click on AS68, a dialog box for parameters will come
up. You can then type "-u -l myfile.s" and click on OK to
run the program. Object files fill be generated and control
returns to the desktop upon completion of the assembly.
Q I have a program where I am drawing my own dialog boxes and
menu by constructing the object tree and calling OBJC_DRAW.
The problem is that when I draw the dialog box, the menu pops
down. I have tried everything to prevent this. What is
happening?
A We suspect what is happening here is that you may be passing
the address of the menu rather than the dialog box. If you
have the level set to MAXDEPTH, everything including the
dialog box over a popped down menu may be drawn. Double
check what you are passing to the objc_draw.
Q I have a dialog box with an editable field. When I try to
put string to initialize the data, everything is messed up.
It seems like the pe_text pointer is pointing to the wrong
place!
A The OBSPEC field of the editable object points to a TEDINFO
structure. In this structure there are three pointers: in
order they are 1) to a string containing the actual text, 2)
to the template, and 3) to a character validation field.
Beyond getting the proper pointer, another problem you may
encounter is that the string is a fixed length. You may be
moving data into it which is longer than was created at the
time you defined the text in the resource construction set.
Q I am running the batch program and get a bus error after
c0.prg has been running a little while compiling my program.
Could this be a bug in the compiler.
A A bug is always possible but here are a few other things to
suspect when a problem like this occurs. The batch program
will abend if it cannot find a specified program to load.
You may also have an include file with something illegal.
That might explain why things proceed through the
pre-processor in abort in the first compile step. Another
thing to check is if you are running out of space on the disk
from which the compiler is running. Each step of the compile
creates some intermediate files which require space. It is
possible to specify to the compiler which drive to which it
writes the intermediate files.
Q I am transferring files from my IBM PC to the ST using
kermit. ASCII files come over o.k. but binary files are
messed up.
A When you transfer binary files you must tell the server to
SET FILE TYPE BIN. You must also tell kermit on the ST to gi
(get image) or si (send image).
Q I am using ICED.PRG to design my icons for use in my resource
file. How do I load these icons into the RCS?
A As an example, let us consider that you are in the RCS and
have created a dialog box. Drag the icon type from the parts
box into your work area. Select the work area and select the
icon you have just moved down. Bring down the menu under the
file heading and select the open. At this point the open
item will not load a new resource but will load in and link
the data for the icon file you select in the file selector.
Q What documentation errors do you know about in the
Hitchhiker's Guide to the BIOS?
A The current Hitchhiker's Guide shows the initial PC being set
from $FC0000 and the initial SP from $FC0004. These values
are reversed.
Hitchhiker's Guide is wrong in two places about the GEMDOS
call $20 to set supervisor mode. The flag to merely test the
current mode is $1 and not the $FFFFFFFF specified. The
latter will crash the system. Second, the returned value
from this function is $0 for user mode and $FF for supervisor
mode, not $0 and $1 as documented.
Q To get started writing my program I need some more example
programs. Where can I find some?
A We recommend that you get onto Compuserve and take a look at
the Atari 16-bit SIG and also the Atari developer's SIG. For
the latter, type GO PCS57, and read the membership
information. We are constantly uploading example programs
into the data libraries as well as other developers. These
programs are available for download to your system.
Q I am trying to redirect standard output by using the Fforce
function. Gemdos is checking the handle for a number less
than 6 and reporting an error. How do I redirect the
console?
A The new handle which you pass this function must be greater
than 6 or less than 0. Values of -1, -2, -3 correspond to
CON, AUX and PRN.
Q How can I make a listing of my assembler program?
A There is a way to make AS68 write a listing file to disk. To
do this you must add the parameter -P and specify the output
file name following the input file name with >filename. Here
is an example which may work for you.
AS68 -P -L -U file.s >list.txt
You can do this either from a batch file or you may install
AS68 as a TTP and do this from the desktop.
Q I am trying to compile the simple example C program that just
uses printf to output "hello world". I keep getting
undefined symbols during the compile and the object will not
link. What is wrong?
A The most likely cause of the compile errors is that you are
missing the header file STDIO.H. Be sure that at the
beginning of your source file that you put the following
statement in:
#include "stdio.h"
Problems with the link may be caused by not specifying all
the files that are required. Here is the bare minimum you
should have for a C program that is not a GEM application:
gemstart.o,(your object),gemlib,libf
Q Why is the return key not returned by the getchar function?
A When Digital Research wrote the 68k run time libraries for
the Alcyon C compiler they used the Unix new line definition
for terminating input. In a generic system the return key
would generate the sequence CR LF. The run time libraries
throw away the CR and count on the LF coming through. The
only way to get around this problem is to use the unfiltered
bios or dos input from console. The scanf function is
similarly afflicted. Instead of forcing the user to
terminate input with control-J, build a buffer of characters
terminated by a null character using the bios and bdos. Pass
this string to sscanf which acts only on the string and does
no keyboard input.
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