how to query window handles of external programs? (multiplatform)

[Martin V]

After starting an external program from my Lazarus app with tProcess, I know the external process ID but not the window handle. To have the ability of sending messages to the external program, I need to query the window handle of the main form of the external program.

In Windows, I can query reverse the process ID from the window handle. So I need to query all open windows by using GetWindow or enumWindows and compare the process ids with the id I am searching for and - bingo I have the window handle.

But these functions are not for multiplatform programming.

The goal would be a multiplatform function MainWindowHandleFromProcessID. Any ideas?

(I know that an alternative concept of inter-program communication is IPCServer. It will fit my purpose, but I am interested in this anyway.)

[Thaddy]

The problem is that not every platform uses the concept of "window handles". So basically if you want it implemented in a truely cross-platform way you are at a loss.

[balazsszekely]

There are many ways to communicate between two processes: sockets, shared memory, files, memory mapped files, named pipes, message queues, etc. So it can be done cross platform way, just not with window handles.