No complaint about the check and the intentions, just the nature of the
error message. A bus error deep in code you didn't write is hard to track
down (like hours of work). In this case I was able to find it because I
knew the code worked before some rearranging.
The text you quote below is helpful once you know it's related to
FrmDrawForm which wasn't the case until it was fixed :-).
Thanks,
LL
On Sat, 30 Sep 2000 [EMAIL PROTECTED] wrote:
>
>
> That bus error is intentional. When there is no actively determined "draw
> window", Palm OS jams an invalid pointer into the variable that normally points
> to the draw window. Then, if anything tries to perform an operation on the draw
> window before re-establishing what that window is, it gets a bus error.
>
> This approach was taken as it was deemed more sure-fire that attempting to add
> asserts all over Palm OS to detect that the draw window was not set and showing
> an error message.
>
> I'm not sure where this is documented, but a search of the KnowledgeBase turns
> up:
>
> <http://oasis.palm.com/dev/kb/manuals/1719.cfm>
>
> FrmDrawForm
>
> On release 3.5, FrmDrawForm erases the window's rectangle before
> it draws, so you must perform custom drawing after the call to
> FrmDrawForm, not before. If you have drawn before the call to
> FrmDrawForm, your changes are lost. On debug ROMs, the window
> handle is invalid until FrmDrawForm is called so that draws
> before FrmDrawForm result in a bus error.
>
> -- Keith Rollin
> -- Palm OS Emulator engineer
>
>
>
>
>
>
> Laurence Lundblade <[EMAIL PROTECTED]> on 09/30/2000 03:39:23 PM
>
> Please respond to "Palm Developer Forum" <[EMAIL PROTECTED]>
>
> Sent by: Laurence Lundblade <[EMAIL PROTECTED]>
>
>
> To: "Palm Developer Forum" <[EMAIL PROTECTED]>
> cc: (Keith Rollin/US/PALM)
> Subject: draw before FrmDrawForm in color debug ROM
>
>
>
> Seems the PalmOS 3.5 debug ROM along with 3.0a7 emulator has a very
> unpleasent error response to an appropriate error check.
>
> When (incorrectly) attempting draw operations like WinSetPattern and
> FldDrawField *before* a FrmDrawForm, you get a bus error.
>
> This doesn't seem to happen with any other ROM so maybe it's a debug check
> gone wrong?
>
> LL
>
>
>
>
> --
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>
>
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