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Using TRANSFER with API calls

Posted by Patrice Terrier 
Patrice Terrier
Using TRANSFER with API calls
June 24, 2009 01:18PM
Useful TIP

You probably know that the WL API keyword returns "only" a long integer whatever the real value returned by the underlaying api call.

What to do, if the returned value is a pointer to a structure or indeed a real value?

Then the WL Transfer comes to rescue, here is an example showing you how to turn the Long integer (4-byte int) into a Single 4-byte real.

// Example based on the GDImage encapsulation
FUNCTION ZI_GetZoomValue(LOCAL hWnd is int)
nRet is int = ZI_GetProperty(hWnd, ZI_ZoomFactor)
rValue is 4-byte real       // <----------
Transfer(&rValue, &nRet, 4) // <----------
IF rValue < 0.001 THEN rValue = 1
RESULT rValue
...
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