"MousePreview" monitoring mouse clicks?

[ArminLinder]

Hi,

on a form I wish to clear the status line when either any button or key is pressed anywhere, or a mouse click occurs.

For keys, this was not difficult: set KeyPreview to true, and in the FormKeyUp handler do the job.

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
2. begin
3.   EditStatus.Text := 'Cleared by keypress';
4. end;
5.  
6. procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
7.   Shift: TShiftState; X, Y: Integer);
8. begin
9.   EditStatus.Text := 'Cleared by mouse click';
10. end;
11.  

As you can see, I tried the same with OnMouseUp, but had no good results, the event does not fire, if the mouse is over any visible control, e.g. a button or even a panel, which is almost always the case.

Is there an alternative to defining an OnMouseUp handler into each and every control, something like a "MousePreview" like there is a "KeyPreview"?

Thnx

Armin.

[balazsszekely]

Hi Nimral,

You're under windows, just create a mouse hook and you're good to go. If you find the hook a difficult solution, with a timer watch the mouse position(Mouse.CursorPos) translate to your form(ScreenToClient) then calculate which component is below the mouse. The third solution is to redirect every MouseUp to a single event at least for those component you're interested in. The second and third solution are cross-platform.

[ArminLinder]

Thanks, GetMem,

from what I see here ...

http://stackoverflow.com/questions/25482429/hooking-the-mouse-and-keyboard-in-lazarus

creating a mouse hook doesn't seem to be too much of work, but it ruins the platform-independentness I have right now.

Solution #2: haven't tried this yet, but as far as your suggestion goes, I'd be able to track the mouse position, OK, but how would I detect a mouse click then? I don't see how this approach could help me.

Solution #3: that's exactly what I'd like to avoid, having to overwrite each and every control's OnMouseUp.

Let's see if someone else has an additional approach, if not, I'll implement #1.

Thanks,

Armin.

[balazsszekely]

Solution #3: that's exactly what I'd like to avoid, having to overwrite each and every control's OnMouseUp.

I'm not sure what do you mean by overwrite here? OnFormCreate, with a recursively function, loop through form controls and assign a common OnMouseUp to each control you're interested in. This can be done selectively(only for buttons for example, or for a mixed type of controls tagged with a unique Tag). When OnMouseUp is fired just check the sender(tag, name) and take the appropriate action. I don't know what exactly are you trying to achieve but it shouldn't be to difficult with the above method.

[ArminLinder]

I see your point.

You still overwrite each and every control's OnMouseUp, but you don't do it by hand, which is kind of a progress.

Problem I see: this move is quite unexpected for anyone modifying my code in the future, including me in a year's time or so :-) So if someone decides to define his own MouseUp event for any control, my routine would silently reverse his definition on FormCreate.

I still don't like the approach, though you showed me some kind of automating it :-)

No bad words, just a matter of taste :-)

Greetz, Armin.

[balazsszekely]

@Nimral

I still don't like the approach, though you showed me some kind of automating it :-)

You can make it fully automated. I mean if somebody creates a MouseDown event from the designer, you can redirect to this event after it was catched on the generic event.

Ok. I'm not gonna insist further. 

[Sergei]

Another possible solution is here: http://forum.lazarus-ide.org/index.php?topic=16843.0

It registers a global hook for user events and seems cross-platform (I'm on Win 64).

Code: Pascal  [Select][+][-]

1. uses
2.   ..., Forms, LMessages;
3.  
4. procedure TForm1.FormCreate(Sender: TObject);
5. begin
6.   Application.AddOnUserInputHandler(@MouseHook);
7. end;
8.  
9. procedure TForm1.FormDestroy(Sender: TObject);
10. begin
11.   // To prevent possible system resource leaks
12.   Application.RemoveOnUserInputHandler(@MouseHook);
13. end;
14.  
15. procedure TForm1.MouseHook(Sender: TObject; Msg: Cardinal);
16. begin
17.    if (Msg <> LM_MOUSEMOVE) and (Msg <> LM_NCMOUSEMOVE) then Exit;
18.  
19.   // Do stuff
20. end;
21.  

[741]

I just tried this technique and I get "Error variable identifier expected" as follows

TfrmMain = class(TForm)
   ...
procedure MouseHook(Sender: TObject; Msg: Cardinal);
   ...
end;
   
   
procedure TfrmMain.FormCreate(Sender: TObject);
begin
...
   Application.AddOnUserInputHandler(@MouseHook); //Error Variable Identifier expected
...
end;

[Remy Lebeau]

Code: [Select]

Application.AddOnUserInputHandler(@MouseHook); //Error Variable Identifier expected

Did you make sure there is not another identifier named MouseHook in scope somewhere?  Try using a more unique name, like MyMouseHook or DoMouseHook.  Or, try qualifying the method: @Self.MouseHook.

[741]

Hi

Thanks for the input. This still fails (with the same error) - here is a simple test case.

Code: Pascal  [Select][+][-]

1.    TTest = class
2.       procedure MouseHook_SJB(Sender: TObject; Msg: Cardinal);
3.       procedure TestHook;
4.    end;
5. ...
6. ...
7. procedure TTest.TestHook;
8. begin
9.   Application.AddOnUserInputHandler(@Self.MouseHook_SJB);
10. end;
11.  

Also, I notice that omitting the @ allows compilation

Code: Pascal  [Select][+][-]

1. procedure TfrmMain.FormCreate(Sender: TObject);
2. var
3.    strIniFileFullName: string;
4. begin
5.    Application.AddOnUserInputHandler(@Self.MouseHook1);  //ERROR
6.    Application.AddOnUserInputHandler(MouseHook1);        //NO Error
7.    Application.AddOnUserInputHandler(@MouseHook1);       //Error
8.  

I am trying to recall - Is the procedure name itself a pointer?


UPDATE: Omitting the @ seems to make it work.

[dseligo]

Code: [Select]

   Application.AddOnUserInputHandler(@Self.MouseHook1);  //ERROR
   Application.AddOnUserInputHandler(MouseHook1);        //NO Error

I am trying to recall - Is the procedure name itself a pointer?


UPDATE: Omitting the @ seems to make it work.

You use mode Delphi.

If you use mode Delphi than you omit @, otherwise (in mode ObjFPC) you put @.

See here (number 2): https://www.freepascal.org/daily/doc/prog/progse76.html
And here (number 1): https://www.freepascal.org/daily/doc/prog/progse74.html

[741]

Thank you!