Why is Scripting.Dictionary.Add(hwnd) munging its reference?

[MarkRobbins]

I am posting this to get information on other gotchas like this... what shouldn't I be passing to a dictionary?

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#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>


global $gc_oForms=ObjCreate("Scripting.Dictionary")
global $make_error_happen=false
$make_error_happen=true

; Example shows destruction of hwnd by passing it to a dictionary object .Add, evidently by ref
; Is there something to know about handles and dictionaries?
;
Example1()


; example 1
Func Example1()
Local $msg
;
local $hGui=GUICreate("My GUI") ; will create a dialog box that when displayed is centered
;A valid hwnd
MsgBox(0,'Handle1',$hGui)
if $make_error_happen Then
     ;pass handle directly which will mung the $hGui variable up
     $gc_oForms.Add('stuff',$hGui)
     ;$hGui is invalid now, has been transformed - Autoit at fault or Dictionary?
     MsgBox(0,'Handle2',$hGui)
     MsgBox(0,'Handle3',$gc_oForms.Item('stuff'))
endif
local $cid=GUICtrlCreateButton("Darn Button",0,0)
;if $make_error_happen then this next call fails
local $p=ControlGetPos($hGui, "", $cid );xywh
if @error then
     MsgBox(0,"ERROR HERE",'@error:'&@error)
endif
;
GUISetState(@SW_SHOW) ; will display an empty dialog box

; Run the GUI until the dialog is closed
While 1
     $msg = GUIGetMsg()

     If $msg = $GUI_EVENT_CLOSE Then ExitLoop
WEnd
GUIDelete()
EndFunc ;==>Example1

[BrewManNH]

It's not "munging" it up, it's displaying it as a decimal number instead of a hexadecimal number.

Change the second message box to this "MsgBox(0, 'Handle2', hex($hGui))" to see what I'm talking about, you will see that the 2 numbers are the same.

EDIT: It is converting the variable from a handle to a number though, so I suppose that could be a bug, although I'm not sure if it's AutoIt or the dictionary object that is doing it. This is why the controlgetpos isn't working, you no longer have a handle reference, you have a number.

Edited March 28, 2013 by BrewManNH

[kylomas]

MarkRobbins,

Try this

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#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>


global $gc_oForms=ObjCreate("Scripting.Dictionary")
global $make_error_happen=false
$make_error_happen=true

; Example shows destruction of hwnd by passing it to a dictionary object .Add, evidently by ref
; Is there something to know about handles and dictionaries?
;
Example1()


; example 1
Func Example1()
Local $msg
;
local $hGui=GUICreate("My GUI") ; will create a dialog box that when displayed is centered
;A valid hwnd
MsgBox(0,'Handle1',$hGui)

; force type to "hwnd"

if $make_error_happen Then
     $gc_oForms.Add('stuff',hwnd($hGui))                
     MsgBox(0,'Handle2',$hGui)
     MsgBox(0,'Handle3',hwnd($gc_oForms.Item('stuff')))
endif
local $cid=GUICtrlCreateButton("Darn Button",0,0)
;if $make_error_happen then this next call fails
local $p=ControlGetPos($hGui, "", $cid );xywh
if @error then
     MsgBox(0,"ERROR HERE",'@error:'&@error)
endif
;
GUISetState(@SW_SHOW) ; will display an empty dialog box

; Run the GUI until the dialog is closed
While 1
     $msg = GUIGetMsg()

     If $msg = $GUI_EVENT_CLOSE Then ExitLoop
WEnd
GUIDelete()
EndFunc ;==>Example1

kylomas

edit:spelling

Edited March 28, 2013 by kylomas

[BrewManNH]

@kylomas

Nice approach, I never knew about the HWnd function.

[kylomas]

Thanks...

[MarkRobbins]

@kylomas

The HWnd($hGui) solution operates the same as assigning $hGui to a var you know will get trashed, and then passing that. AFAIK a Scripting.Dictionary should be able to hold any type and be keyed on any type that supports == comparison (ie no Arrays).

Poking around I found this interesting:

local $h=WinGetHandle(...;Get a valid hwnd however you like

;make sure the window gets destroyed
WinClose($h)
IsValidHwnd($h);==false

Func IsValidHwnd($h)
if int('0x'&HEX($h))==0 then ; this part is interesting, value of hwnd is now zero since it is closed
return false;
endif
return true;
EndFunc

I have always been looking at hwnds as special ints, not PVOIDS. Which makes me wonder how this is implemented - things get so confusing with memory these days... does windows have a dedicated block that grows (so that invalid handles are left to point at zeroed memory)?

AutoIt must be confusing me, since Hwnd(<arbritrary int>) will produce a zeroed Hwnd if the window does not exist, which I am pretty sure is not the case in C.

Anyhow, I will just put things in a dictionary 'by proxy' whenever I am unsure. Having an HWnd transformed is not expected behavior though, I guess complex AutoIt Types are not capable of being held by Scripting.Dictionary.

[BrewManNH]

$hGUI is is a Windows handle, represented by a hex number, although it's not a number or a string. The dictionary add appears to be doing a ByRef with the number when it's added to the dictionary object, and it's taking the hex number as a string, which converts the original handle to a string.