Psychic debugging: Why doesn't my program show up when I call ShellExecute?
This question came in from a customer (paraphrased):
If I run my program from the command prompt, it works great,
but if I run it from my launcher via ShellExecuteEx,
it never appears.
See how good your psychic powers are at solving this problem
before I give you the second question that gives away the answer.
Any luck?
Here's a second question from a different source (but which
coincidentally came in the same day).
I'm trying to use ShellExecute to open a document.
The function succeeds (returns a value greater than 32),
but I don't get anything on the screen.
if (ShellExecute(Handle, NULL, FileName, NULL,
NULL, NULL) <= (HINSTANCE)32) ...
The problem the second person is having lies in the last parameter
to the ShellExecute function.
It's nShowCmd, which is supposed to be an
SW_* value, but which this person is passing as
NULL.
It so happens, that the value zero corresponds to
SW_HIDE, which explains why the program doesn't
appear: You told it to run hidden!
Now go back to the first problem.
Do you see what the person most likely did wrong?
The code probably went like this:
SHELLEXECUTEINFO sei = { sizeof(sei) };
sei.hwnd = hwnd;
sei.lpVerb = TEXT("open");
sei.lpFile = pszFile;
ShellExecuteEx(&sei);
Since the sei.nShow member was not explicitly
set, the value was implicitly set to zero by the incomplete
initializer.
And as we noted above, zero means SW_HIDE.
It turns out my psychic debugging was correct.
That was indeed the source of the first person's problem.
Now you can use your psychic powers, too.
