AutoHotkey Community

[TL]

I need some help sending and returning strings using the SendMessage() and OnMessage() calls. My objective is to send a text string via lParam and have a string returned through lParam. I'm basing this approach on the following statement under the "PostMessage / SendMessage" entry in the AutoHotkey Help:
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A string may be sent via wParam or lParam by specifying the address of a variable. The following example uses the address operator (&) to do this:
SendMessage, 0xC, 0, &MyVar, ClassNN, WinTitle
In v1.0.43.06+, a string put into MyVar by the receiver of the message is properly recognized without the need for extra steps.
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Based on this statement I assume that AHK is handling the memory allocation and pointer issues related to passing strings between scripts.

My code looks something like this:

Sending script:

[Helpy]

Perhaps a DllCall to lstrcpy...
There might be a simpler way, but I don't see one right now.

[Chris]

As you know, a script can send a string to another script via SendMessage, OnMessage, and WM_COPYDATA (for anyone else reading, a working example is at the bottom of the OnMessage page).

By contrast, a script cannot simply send the address of one of its variables or strings to another script because each script is a separate process with its own address space. There are several ways to work around this, but probably the easiest is to use WM_COPYDATA to go in both directions: sender to receiver, and vice versa.

[Barney9]

Please help me understand this script. With lstrcpy you create a buffer that all processes can access? Then you send its memory adress to the receiver script via sendmessage? Who deletes the buffer after your script has finished using it?

Thank you!

[PhiLho]

I suppose you are talking about the script referenced by Chris...
lstrcpy doesn't create a buffer, that's the VarSetCapacity just above which does that, and it is local to the script.
Note that the lstrcpy is in the Receive part, it is to get the memory whose address in given in the COPYDATA message.
The Send part puts the address of a string in the script in the sent message. The buffer referenced by the message is seen as short-lived, receiver must copy the data to private memory as soon as possible.
Microsoft tells "The lParam parameter is valid only during the processing of the message." which, I suppose, means than upon processing the next Windows message (whatever it is), the buffer it points to is no longer available.
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vPhiLho := RegExReplace("Philippe Lhoste", "^(\w{3})\w*\s+\b(\w{3})\w*$", "$1$2")