Filtering shortcut in eventFilter not working

[mpergand]

Hi all,
I'm trying to block/filtering shortcuts regarding some condition in a event filter method at application level, but it has no effect.

(pseudo) code showing what i'm doing:

bool Application::eventFilter(QObject *obj, QEvent *event)
{
if(event->type() == QEvent::ShortcutOverride)
        {
         QAction* action=actionWithShortcut(obj,event); // get the action 

          if(action)
            {
             action->setEnabled(false); // disable it
             return true;  // has no effect
            }
...

anyway, the shortcut is triggered :(

My goal is to intercept shortcuts before there're triggered, I thought an event filter could be a good way but to no avail.

Any idea ?

[SGaist]

Hi,

Shouldn't that be QEvent::Shortcut ?

[mpergand]

Hi @SGaist

I tried allready, such event never occured ...

For a single key stroke, I see two ShortcutOverride event:

shortcut override "Couper" "Ctrl+X" TextEdit(0x7f8fae45a5d0)
shortcut override "Couper" "Ctrl+X" TextDocWindow(0x7f8fae459c80)

Maybe I need to filter in the widgets too ?

[SGaist]

Something's not clear, why do you want to disable the action that is associated with the shortcut when you actually call the shortcut ?

[JonB]

@SGaist
I wondered that earlier too :) I think you can ignore the action->setEnabled(false); // disable it, I read the OP's question as why does return true; // has no effect have no effect?

[mpergand]

@SGaist said in Filtering shortcut in eventFilter not working:

why do you want to disable the action that is associated with the shortcut when you actually call the shortcut ?

Yes and I want that the action was not triggered (logical ?)
Why ? yes I know, it's not the common way to do.
Actually, I try to implement a responder chain for the menu management.

What I see, is that the action method is called so I need an extra test in it:

void Application::menuAction(QAction* action)
{
    // validateAction dans event filter sans effet
// test action state
    if(!action->isEnabled()) return;
...

In addition on Mac, the menu is flashing but no action takes place in fact.
But if I do the same key stroke a second time, the action is not triggered, so the action state (disabled) is not take in account immediately in the event filter.
That's why I would like to discard the shortcut event.

[SGaist]

Again, that sounds counter-intuitive and convoluted. Why not just disable the action when it should not be used ?

What chain do you want to build with that ?

[mpergand]

It turns out, that the filter works well, if I return yes in the event filter, the shortcut is not propagated to the TextEdit, so far so good.

The final question is, who triggers the action ?

@SGaist
The "Responder Chain" is a very good paradigm for menu management, unfortunatly not easy to implement in Qt.

[SGaist]

Unless we have a different definition of Responder Chain, it's what Qt implements. Hence my question about what you are trying to achieve.

[mpergand]

@SGaist said in Filtering shortcut in eventFilter not working:

Unless we have a different definition of Responder Chain, it's what Qt implements.

I agree, but does it apply with menu actions ?
What I want to do, is the same thing as validateMenuItem on MacOS.
validatemenuitem

On Mac, this method is called before a menu appears (menuAboutToShow on Qt), but also before a shortcut is triggered, allowing to validate the menu at the time the action occurs.
That what I'm trying to do with a eventFilter.

[SGaist]

With Qt, you usually trigger a signal when conditions are met that you connect to the setEnable of the QAction you want. Or you modify the action object directly.

[Qiang0203]

I think you need to explicitly accept the event to trigger the override, as mentioned in the QKeyEvent doc.
Call "event->accept()" before "return true" may resolve your problem.