| Re: Porting IDL [message #12493] |
Thu, 13 August 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Rose (rmlongfield@my-dejanews.com) writes:
> Hi All (and David Fanning in particular), Sorry Dave, I just happened
> to have a problem with your PROCESS.PRO procedure. :o I used it quickly (on
> my SGI) to produce a *.gif of an image. When I did a view of the *.gif file
> (using xv) , however, I got a black box where the drop down menu is located.
> I've never made a gif file with IDL yet but this is really strange. Does
> anyone else have this experience or is it just another SGI problem?...sigh.
Sigh...
I've found over the years that the best way to find bugs
in your programs is to make a public announcement that they
work. :-(
I can believe that this behavior is happening because the
PROCESS program takes a screen dump of the graphics window
(TVRD) to generate the GIF file. On some workstations this
can be problematic. David Foster has some code called
Safe_TVRD (or something like it) that always does a TVRD
from a pixmap, which is more reliable. I usually like to
do a TVRD from the Z-buffer if I can, because then I
can have access to all 256 colors if I need them.
Unfortunately, adding a lot of convoluted code to
example programs tends to confuse issues rather than
clarify them, so sometimes I opt for the simple solution
that works most of the time instead of the complicated
solution that works all of the time. This makes the
programs easier to follow and still leaves me some
material to put in my book. :-)
The PROCESS program could be improved by adding a
pixmap window and doing the TVRD from that. Then it
really WOULD work the same on PCs and SGI workstations.
As Liam Gumley mentioned yesterday, however, despite my
flippant remarks about "well-written" programs, you have
to test, test, test.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: Porting IDL [message #12512 is a reply to message #12493] |
Thu, 13 August 1998 00:00  |
rmlongfield
Messages: 68
Registered: August 1998
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Member |
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In article <MPG.103b6a1f9fc5c113989833@news.frii.com>,
davidf@dfanning.com (David Fanning) wrote:
> Bernard Puc (bpuc@va.aetc.com) writes:
> Uh, depends entirely on how well you WROTE those applications
> in the first place. My IDL programs run on SGIs and PCs without
> modification. :-)
>
> Cheers,
>
> David
Hi All (and David Fanning in particular), Sorry Dave, I just happened
to have a problem with your PROCESS.PRO procedure. :o I used it quickly (on
my SGI) to produce a *.gif of an image. When I did a view of the *.gif file
(using xv) , however, I got a black box where the drop down menu is located.
I've never made a gif file with IDL yet but this is really strange. Does
anyone else have this experience or is it just another SGI problem?...sigh.
Rose Dlhop...
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
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| Re: Porting IDL [message #12516 is a reply to message #12493] |
Wed, 12 August 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Bernard Puc (bpuc@va.aetc.com) writes:
> Thanks for the replies concerning software version control. Here's
> another query for the collective experience of the group: We are
> considering porting our IDL application to a PC platform (written
> for SGI workstation). Does anybody know if there would be
> significant advantages in time and effort in coding if we ported to
> a Linux platform in contrast to Win95?
Uh, depends entirely on how well you WROTE those applications
in the first place. My IDL programs run on SGIs and PCs without
modification. :-)
Cheers,
David
P.S. Well, this WOULD be true if those damn SGIs used
font sizes correctly. :-)
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: Porting IDL [message #12519 is a reply to message #12516] |
Wed, 12 August 1998 00:00 |
Liam Gumley
Messages: 473
Registered: November 1994
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Senior Member |
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Bernard Puc wrote:
> Thanks for the replies concerning software version control. Here's
> another query for the collective experience of the group: We are
> considering porting our IDL application to a PC platform (written
> for SGI workstation). Does anybody know if there would be
> significant advantages in time and effort in coding if we ported to
> a Linux platform in contrast to Win95?
Here's a few thoughts.
Byte-swapping
-------------
If your application reads any kind of 'binary' data that contains
integer or floating point values, you need to be aware of byte-swapping
(unless the data is in a portable format like ASCII/XDR/HDF/netCDF/CDF).
I typically design the read routine to handle byte-swapping
transparently, so that I don't have to worry about whether I'm on an SGI
or a PC. My usual procedure for reading a binary file is
(1) Open the file
(2) Read a single 'record' into an IDL structure
(3) Decode part of the structure (say date and time) to see if the
values are sensible
(4) If the values are sensible, then proceed with read as normal
(5) If the values are not sensible, byte-swap the entire structure using
SWAP_ENDIAN
(6) Decode the same values as in (3) to see if the values are sensible
(7) If the values are sensible, set byte-swap flag ON. If values are not
sensible, tell the user the file format was not recognized and quit.
(8) Read subsequent records, and byte-swap if the byte-swap flag is set
This is usually only necessary where you had no direct control over the
way the file was created to begin with. If you are responsible for
creating the file, then using one of the portable formats mentioned
previously will make you life *much* easier.
(There is no difference between Windows and Linux regarding
byte-swapping).
Widgets
-------
If your application uses widgets, then as long as you were careful to
allow IDL to lay out the widgets (i.e. you used XSIZE/XOFFSET/XPAD etc.
keywords sparingly), you should be ok. The bottom line is that you have
to suck it and see (try your application on the PC and see what it looks
like). If you use the standard Motif window manager under Linux (*not*
FVWM et al.), the chances are good that the widgets will look pretty
much like they do on the SGI. If you use a standard font for widgets,
e.g.
widget_control, default_font = '7x13'
then your chances are even better. Try Linux and Windows, and see which
one looks better to you.
Direct graphics vector fonts
----------------------------
If you are creating direct graphics with vector fonts, then pick a
standard size and stick to it, e.g.
device, set_character_size = [ 6, 9 ]
Otherwise the graphics you have carefully crafted on the SGI will look a
lot different in Linux or Windows, or any other Unix platform for that
matter.
Colors
------
Your safest bet (unless you're of David Fanning caliber!) is to stick
with 8 bit mode. If you can figure out how to handle the various flavors
of 8/16/24/32 bit graphics available on PCs transparently, then my hat
is off to you. Put something like the following in your IDL startup
file:
if !version.os_family eq 'unix' then device, pseudo = 8
device, retain = 2, decomposed = 0
window, /free, /pixmap, colors = -5
widget_control, default_font = '7x13'
device, set_character_size = [ 6, 9 ]
and make sure you use the same startup file on all platforms. These
commands must be executed right at startup, because once you create the
first graphics window, the number of colors is set for the rest of that
IDL session.
Save files
----------
If you want to keep the SGI as your development platform, then you don't
need to send all the application source code to the PC. Just do the
following:
(1) Start a new IDL session on the SGI
(2) Do a .COMPILE on all the application routines (let's say the main
program is myapp.pro)
(3) Save the compiled routines using
SAVE,/ROUTINES,/XDR,FILE='myapp.sav'
(4) Send the binary file myapp.sav to the PC
(5) Start IDL on the PC (using the same startup file as the SGI)
(6) Type
RESTORE,'myapp.sav'
(7) Type
myapp
Cheers,
Liam.
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