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Delphi Interview Questions

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Just like C: You can get a far pointer to your callback procedure (you have to remember to declare it with the "far" qualifier, unless you have {F$+} in effect to force all calls to be far), pass the pointer to the Windows callback function, and there it is. 

Delphi always assumes that the color of the bottom left-hand corner pixel is the background color and should be displayed as transparent. Yes, it took me a while to figure this out. It's not documented anywhere, but if you have the VCL source, you can look at the code in BUTTONS.PAS. 

Based on the number of postings to comp.lang.pascal, it would seem that by far the largest number of problems calling Windows API functions or non-Delphi DLLs are caused by passing Pascal-style strings to functions that expect null-terminated (PChar) strings. This is the first thing you should check if you get a GPF or other strange results when calling an external function. See section 6.11 for more information on which type of strings go where. 

Use the Application.OnException event. Look in the help under "application events" for details of how to create and attach an event handler to the application variable. 

By default, the internal debugger will halt any time there is an exception, even if the exception is trapped by code. This can often be useful for debugging purposes. If it offends you, turn it off. You control it from the Options/Environment menu. 

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