Issue with ListView HWND and GetClassName (Can anyone else reproduce this?)

[JFord]

My attempt to instantiate an LV_Colors object was failing and it led me to breakdown the cause to the inability of GetClassName to get a handle on the ListView control based on its HWND. The following short code works perfectly on my laptop, but it will fail on less powerful machines randomly, but often.

Code: Select all

Gui Add, ListView, HwndThisHWND, A|B
VarSetCapacity(Class, 512, 0)
DllCall("GetClassName", "Ptr", ThisHWND, "Str", Class, "Int", 256)
If (Class == "")
	MsgBox Failed
Gui Destroy
ExitApp

I have thousands of other observations, but I will stop here and wait for feedback.

[swagfag]

it led me to breakdown the cause to the inability of GetClassName to get a handle on the ListView control based on its HWND.

doubt thats the problem. also how would u even know if thats the case? u arent checking it. and no, If (Class == "") is not checking it

If the function fails, the return value is zero. To get extended error information, call GetLastError function.

so check the return val, A_LastError and since its DllCall were talking about might as well check ErrorLevel while ure at it

also, just use WinGetClass theClass, ahk_id %theHwnd% but again - this probably isnt the source of ur issues

[JFord]

Thanks for your reply. I am not sure why I did not see it earlier.

I improved my error checking to determine that the underlying error is 1400 (0x578) ERROR_INVALID_WINDOW_HANDLE. Don't know how much we learned from that. I did also confirm that using WinGetClass worked perfectly.

The good news (for me) is that this is all moot as I have recognized that I don't need to take this route at all and so my problem is resolved without every understanding why this code failed.