AHK Window is findable, but SendMessage (Send_WM_COPYDATA) sometimes fails

[JoeSchmoe]

Hello,

Hello, I'm trying to use SendMessage to send messages from one AHK script to another. I'm using the classic Send_WM_COPYDATA code that maybe Chris wrote back in the day.

It works most of the time, but sometimes SendMessage returns "Fail." Here's the code I'm using:

Code: Select all

HeyJarvis(Object) 
{
	TargetScriptTitle = SponsorFox.ahk ahk_class AutoHotkey
	stringified := JSON.Dump(Object)
	result := Send_WM_COPYDATA(stringified, TargetScriptTitle)
	if result = FAIL
		MsgBox SendMessage failed. Does the following WinTitle exist?:`n%TargetScriptTitle%
	else if result = 0
		MsgBox Message sent but the target window responded with 0, which may mean it ignored it.
}


Send_WM_COPYDATA(ByRef StringToSend, ByRef TargetScriptTitle)  ; ByRef saves a little memory in this case.
; This function sends the specified string to the specified window and returns the reply.
; The reply is 1 if the target window processed the message, or 0 if it ignored it.
{
    VarSetCapacity(CopyDataStruct, 3*A_PtrSize, 0)  ; Set up the structure's memory area.
    ; First set the structure's cbData member to the size of the string, including its zero terminator:
    SizeInBytes := (StrLen(StringToSend) + 1) * (A_IsUnicode ? 2 : 1)
    NumPut(SizeInBytes, CopyDataStruct, A_PtrSize)  ; OS requires that this be done.
    NumPut(&StringToSend, CopyDataStruct, 2*A_PtrSize)  ; Set lpData to point to the string itself.
    Prev_DetectHiddenWindows := A_DetectHiddenWindows
    Prev_TitleMatchMode := A_TitleMatchMode
    DetectHiddenWindows On
    SetTitleMatchMode 2
    SendMessage, 0x4a, 0, &CopyDataStruct,, %TargetScriptTitle%  ; 0x4a is WM_COPYDATA. Must use Send not Post.
    DetectHiddenWindows %Prev_DetectHiddenWindows%  ; Restore original setting for the caller.
    SetTitleMatchMode %Prev_TitleMatchMode%         ; Same.
    return ErrorLevel  ; Return SendMessage's reply back to our caller.
}

WinExist IS able to find the target script (only one window matches), but SendMessage returns "FAIL" SOMETIMES.

AHK 1.1.24.2
Wind7 Pro 64

Any ideas?