Re: trying to understand the run loop

[Richard Frith-Macdonald]

On 8 Mar 2006, at 02:15, Lloyd Dupont wrote:

> My application is not a GNUstep application at all.
> Yet it uses Foundationand some of AppKit classes.
> Now I'm trying to setup a framework so that everything works as  
> well as possible.
>
> Problem is, I don't have an explicit run loop, event pump in my  
> developement environment, it's all event based.
> Yet I registerer ed an event handle on the application Idle event  
> and manage to simulate a run loop with that.
>
> I try to mimic the code below in my code and, I would welcome any  
> comment, addition:
>
>
> // pseudo code of my application, am I missing something?
>
> NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
> NSUndoManager *undoManger = GetUndoManager();
> [NSApplication shared];
> [pool release];
>
> while(event = GetEvent())
> {
>    pool = [[NSAutoreleasePool alloc] init];
>
>    DoEvent(event);
>
>    GSNotifyASAP(); // no I won't use [runLoop runModeBeforeDate] it  
> mess up my application
>    GSNotifyIdle();

You don't want to be using internal API from the library ... if  
runModeBeforeDate is causing a problem you need to provide a bugfix  
(or at least sample code to allow someone to replicate the bug and  
fix it).  Current code in svn has several mingw32 cleanups and might  
work fine for you anyway.

>    while([undoManager groupingLevel] > 0)
>        [undoManager endUndoGrouping];
>
>    [pool release];
> }


There are two approaches ...
The one using standard APIs would be something like above (polling  
from within windows event handling) ...

NSUndoManager *undoManger = GetUndoManager();
NSRunLoop *loop = [NSRunLoop currentRunLoop];
NSDate *past = [NSDate distantPast];
[NSApplication shared];

while (event = GetEvent())
{
   pool = [NSAutoreleasePool new];

   DoEvent(event);

   [runLoop acceptInputForMode: NSDefaultRunLoopMode beforeDate: past];

   while ([undoManager groupingLevel] > 0)
       [undoManager endUndoGrouping];

   [pool release];
}

The alternative, running from within a runloop, requires a bit more  
setup, with a class to handle windows message callbacks ...

@implementation MyWatcher
- (void) receivedEvent: (void*)handle type: (RunLoopEventType) extra:  
(void*)extra forMode: (NSString*)mode
{
  DoEvent(extra);
}
@end

NSUndoManager *undoManger = GetUndoManager();
NSRunLoop *loop = [NSRunLoop currentRunLoop];
MyWatcher *watcher = [MyWatcher new];

[loop addEvent: NULL type: ET_WINMSG watcher: watcher forMode:  
NSDefaultRunLoopMode];
[NSApplication shared];
[loop run];



While the above relies on a GNUsterp extension to NSRunLoop, which  
may be deprecated and then removed in later releases, it will at  
least be around for a while and will not be removed without some  
equivalent being put in place.  However, the first approach (using  
only standard APIs) is probably best.