I think this message from Bob Ebert will help you. Even though it is
specifically about WinRGBToIndex, I've found that it applies to a
number of the WinXXX functions.
DeAnna
>
...
> >
> >Background: On DEBUG ROMs only, when someone sets the draw
> window to NULL,
> >we instead set it to an invalid address. (0x80000000) We did this
> >deliberately so that we would immediately catch any code that
> tries to draw
> >too soon, or otherwise use the the DrawWindow when it is
> invalid. That is,
> >instead of reading/writing through NULL (which works), now it
> tries to read
> >through an invalid address and immediately generates a bus error.
> >
> >Before I go on, I should say that this was a very good idea, and
> it helped
> >us catch a lot of drawing problems related to the bad draw window.
> >
> >HOWEVER, in the case of WinRGBToIndex, that function tests to
> see that the
> >draw window is non-NULL before using it. If it is NULL
> (invalid), then it
> >goes directly to the screen hardware to get the palette. That is,
> >WinRGBToIndex is intended to work even when the DrawWindow is not valid.
> >
> >UNFORTUNATELY (you can see this coming, right), the 'bad address' that we
> >set the draw window to is not NULL, so WinRGBToIndex thinks the
> draw window
> >is valid and tries to use it... and then boom, you get the bus error.
> >
> >Obviously we need to find the few places where the OS tests the
> draw window
> >against NULL and make sure it *also* tests against the invalid address.
> >
> >Sigh... I don't know what to tell you for now. We blew it.
> The code will
> >work fine on RELEASE ROMs. Until then... well, I suppose you can work
> >around this by explicitly setting the draw window to something
> valid before
> >calling the UI color set function. I think you should do this:
> >
> > WinSetDrawWindow(WinGetDisplayWindow());
> >
> >This will force the draw window to be the 'root' window for the OS, which
> >is the full screen. The palette for this window will always be
> the same as
> >the hardware. It's better to do this than to set the draw window to your
> >form, because you might have a better chance of catching draw-too-early
> >bugs this way.
> >
> > --Bob
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