Technical Q&As

QTICM 12 - Decompressing to Partial window: Bug & Workaround (1-May-95)

Q Under System 7, decompressing directly to a window that is partially "off the screen" (that is, not completely visible) results in a -50 (invalid param) QuickTime error. We can special case when windows are off the screen and decompress into an offscreen GWorld but we would prefer a fix to either QuickTime or System 7.

A The problem you are having is due to a bug in the Image Compression Manager. It fails to clear QDError when starting a decompression job and later checks it to see if it is OK to continue the operation. Something else is setting QDErr and your call fails.

The solution that you can implement now consists of clearing QDErr before calling any of the decompression routines. You can accomplish this by calling QDError (which clears the error after it passes the current value to you) or zeroing the low mem QDerr (0xD6E) by hand.

Future versions of QuickTime will have the fix and will not require that you work around the problem.

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