How do I send CM_/CN_ messages to controls in a cross-platform manner? [SOLVED]

[carl_caulkett]

* Mac Mini M1
* macOS 14.6.1
* Lazarus 3.4
* FPC 3.2.2

Back in my Delphi days, if I wanted to send messages to a control, I would use the WM_ Windows messages and send them to a control's Handle.

Presumably on the Mac this is a non-starter! However, I've just found TRon's excellent post https://forum.lazarus.freepascal.org/index.php/topic,63350.msg479697.html#msg479697 which shows how to use the TApplicationProperties component to intercept messages such as CN_KEYDOWN and CN_KEYUP, received on any control in my app.

This, then, begs the question, is it possible to send similar messages to a control of my choosing, and will this work equally on Mac, Linux and Windows?

[carl_caulkett]

The reason I wanted to send messages to a control was tied up with my problem with macOS insisting on beeping on unhandled keyboard inputs. I managed to mitigate the problem to some extent by holding my TLazVirtualStringTree in a dummy TPageControl which certainly suppressed the beeping on cursor up and down keystrokes. But the beeping returned when I tried to use the LazMouseAndKeyInput.lpk package...

Code: Pascal  [Select][+][-]

1. procedure TMain.PresetTreeKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
2. var
3.   I: Integer;
4. begin
5.   case Key of
6.     VK_PRIOR:
7.       for I := 1 to PresetTreeRowsPerPage do
8.         KeyInput.Press(VK_UP);
9.     VK_NEXT:
10.       for I := 1 to PresetTreeRowsPerPage do
11.         KeyInput.Press(VK_DOWN);
12.   end;
13.   case Key of
14.     VK_PRIOR, VK_NEXT, VK_HOME, VK_END:
15.       Key := 0;
16.   end;
17. end;
18.  

I eventually solved this problem by changing the macOS settings for Sound. All I had to do was to select a destination for "Play sound effects through" that didn't go to a speaker or an audio interface and the beeping vanished, which meant that I could get rid of all of the above malarkey