[SOLVED] NSControls in drawers attached to modal panels under 10.2.8

FROM : Tim Hewett
DATE : Fri Nov 19 18:11:20 2004

Hello,

A while back I reported being unable to get buttons and other
controls to call their action methods when those controls were
located in a NSDrawer attached to a modal NSPanel under
10.2.8. Clicking the button/slider/matrix etc just caused a system
beep with the action method not being called at all.

This was kludged by subclassing the control and providing a
mouseDown replacement which handled all the highlighting
of the button, and the calling of the action method on the target.
Worked fine, but now my app needs to have a NSSlider call an
action method continuously while sliding, which resulted in a
hail of system beep "bullets" like a machine gun... Overloading
mouseDown for NSSlider was getting complex since it is more
than just a button so a different way was found (now I'm a little
further a long the learning curve since last time) by overloading
the sendAction:to: NSControl method instead.

This turns out to be a generic solution for all NSControls that
won't work in modal panel drawers, and doesn't disrupt behaviour
under 10.3 either. This is the code sample:

@implementation MyButton    // inherits from NSButton

- (BOOL)sendAction:(SEL)theAction to:(id)theTarget
{
    if ( !theAction || !theTarget )
        return FALSE;

    objc_msgSend( theTarget, theAction, self );
    return TRUE;
}

@end

It lacks one feature of the normal implementation, where the target
can be nil leading to a search algorithm being triggered to find an
object which supports the particular selector. There are possible
other things missing too, but it works well enough for me.

BTW I don't know why objc_msgSend() has to be used instead of
performSelector:withObject:afterDelay: but it does.

Note that if this is used for NSMatrix then for some reason theAction
and theTarget are always received as nil, so instead do:

    objc_msgSend( [self target], [self action], self );

Works great.

HTH,

Tim Hewett.