How to detect the unknown object stealing a specific shortcut?

Question

In a very complex Delphi 10.4.2 VCL Application, an unknown control or component seems to "steal" the CTRL+A shortcut. In an attempt to detect the object stealing the shortcut, I try using the TApplicationEvents.OnShortCut event handler:

procedure TformMain.ApplicationEvents1ShortCut(var Msg: TWMKey; var Handled: Boolean);
begin
  case Msg.CharCode of      
    VK_A:
      begin
        //CodeSite.Send('TformMain.ApplicationEvents1ShortCut: ', ???);
      end;
  end;
end;

Can this event handler be used to detect the "thief", or which method would you suggest?

Why not searching all .PAS files for the text ctrl or ssCtrl? — AmigoJack
@AmigoJack: That will miss a very large number of all possible scenarios, for instance, when you have a TAction with its Shortcut set to Ctrl+A. That's stored (utterly numerically) in the DFM. — Andreas Rejbrand
@AndreasRejbrand That's true: The Action's CTRL+A shortcut is stored in the DFM as ShortCut = 16449. — user1580348

Andreas Rejbrand Andreas Rejbrand · Accepted Answer · 2021-07-05T13:27:39

There are many ways to implement shortcuts, so there might not be a single quick approach that can catch them all. But the following should cover many (if not most) cases.

All background knowledge you need can be found in Peter Below’s A Key’s Odyssey.

First, if you know that some code is executed as a result of this shortcut, you can put a breakpoint in this code and the call stack will likely tell you all you need to know.

For instance, if I create a new VCL application, add a TActionList, and a TAction with shortcut Ctrl+T and an OnExecute handler which calls the CreateFrog procedure, I can put a breakpoint in this procedure, and I get the following call stack:

Here we immediately see that CreateFrog was called due to an action named aTest with a matching shortcut. In fact, if you go down all the way down to TControl.WndProc (say) you can even see that the T (84) key was depressed (CN_KEYDOWN = 48384):

If you don't have any nice place to put a breakpoint, you can put a conditional breakpoint in TControl.WndProc with condition (Message.Msg = CN_KEYDOWN) and (Message.WParam = 84):

Then, if you run the app and trigger the shortcut, you will be able to step through the source code and see what happens.

How to detect the unknown object stealing a specific shortcut?

1 Answers