Help! DisposeGWorld is killing me!

External Since: Apr 02, 2004 Posts: 6

I am programming a Carbon and classic application.

I am extremely frustrated after eight solid hours chasing a problem, and
still no end in sight. I have boiled the problem down to a single line of
code - a call to DisposeGWorld. The problem is the GWorld is a normally
created Gworld. it is 8 bits in depth, and I gave it a color table to use
(but no device, assuming it will build one). I use the same pmTable value
for many of my other gworlds and pixmaps, as I am using a grayscale color
table for use in generating masks. Anway, the DisposeGWorld call smashes
memory somehow, and shortly thereafter my program goes cosmic, and i can't
figure out why the DisposeGWorld call is ruining my life.

I read about how if you call DisposeGWorld using the currently selected
port, it will kill you. I realize this but i put a GetPort(p); IF p =
gworld_being_discard THEN quit statement so I could catch any stupid error
of this kind.

Anyone else suffered through this? Is there something about 8-bit GWorlds
and their color tables that is particularly tricky?

A prize to whoever helps me solve this first.

edj

External Since: Sep 07, 2003 Posts: 305

In article <BD2C80BB.394F5%edward@magicmouse.com>,
Edward de Jong <edward.RemoveThis@magicmouse.com> wrote:

> I am programming a Carbon and classic application.
>
> I am extremely frustrated after eight solid hours chasing a problem, and
> still no end in sight. I have boiled the problem down to a single line of
> code - a call to DisposeGWorld. The problem is the GWorld is a normally
> created Gworld. it is 8 bits in depth, and I gave it a color table to use
> (but no device, assuming it will build one). I use the same pmTable value
> for many of my other gworlds and pixmaps, as I am using a grayscale color
> table for use in generating masks. Anway, the DisposeGWorld call smashes
> memory somehow, and shortly thereafter my program goes cosmic, and i can't
> figure out why the DisposeGWorld call is ruining my life.
>
> I read about how if you call DisposeGWorld using the currently selected
> port, it will kill you. I realize this but i put a GetPort(p); IF p =
> gworld_being_discard THEN quit statement so I could catch any stupid error
> of this kind.
>
> Anyone else suffered through this? Is there something about 8-bit GWorlds
> and their color tables that is particularly tricky?
>
> A prize to whoever helps me solve this first.
>
> edj

Have you attached any shared resources to it, like a system color table
or the main GDevice? DisposeGWorld will delete that too and make a
serious mess of your app environment. You need to either duplicate
resources or detach them before calling DisposeGWorld. Watch out for
deep disposal on shallow copies too. Your best bet is to step through
it in a debugger and see where the innards point to. At least in
Classic, Macsbug can tell you which heap a pointer or handle belongs to.

The newsgroups comp.sys.mac.programmer.help and
comp.sys.mac.programmer.codewarrior will probably be better resources.
Post some code in one.