RE: drag manager strange behavior

Well… I managed to put a break point in TrackDrag for finder, and it seems Finder is creating another drag.

Could the reason be something I’m doing, or is it a bug in Carbon/Finder.

From: Bryan Prusha [mailto:email@hidden]
Sent: Tuesday, October 30, 2007 7:42 PM
To: Yaron Tadmor
Cc: David A. Lyons; carbon-dev List
Subject: Re: drag manager strange behavior

Are you sure Track Drag isn't being accidentally invoked within your app? There's definitely another DragRef being used with the extra tracking calls. It would be worth setting a breakpoint on TrackDrag in Finder too, just in case it's managing to invoke another call somehow as well.

On Oct 30, 2007, at 2:36 AM, Yaron Tadmor wrote:

I’m dragging a file from the Finder, so I have no control over the code initiating the dragging. I’m just handling the track and receive in my app.

From: David A. Lyons [mailto:email@hidden]
Sent: Tuesday, October 30, 2007 11:23 AM
To: Yaron Tadmor; carbon-dev List
Cc: Bryan Prusha
Subject: Re: drag manager strange behavior

Where are you dragging from? Do you control the code that calls TrackDrag? If so, check if it's being called twice.

I have seen a situation where a Carbon application was creating+tracking a drag in response to a kEventMouseDragged Carbon event. This event means "the mouse moved while the button was down." It turned out to be perfectly possible to receive more than one kEventMouseDragged event even if the application called TrackDrag in response to the first one. The solution was to add a small amount of logic so that following each kEventMouseDown for our view, we would only start a drag in response to one kEventMouseDragged.

Cheers,

--Dave

On Oct 30, 2007, at 1:18 AM, Yaron Tadmor wrote:

Hi,

Checking what you asked I see a second drag reference is created. This is the print out from the start and end of the drag track and receive handlers:

track handler: 0x58000000

end track

track handler: 0x58000000

end track

recieve handler: 0x58000000

end recieve

track handler: 0x58000000

end track

track handler: 0x58000000

end track

track handler: 0x5c000000

end track

track handler: 0x5c000000

end track

track handler: 0x5c000000

end track

track handler: 0x5c000000

end track

recieve handler: 0x5c000000

end recieve

track handler: 0x5c000000

end track

track handler: 0x5c000000

end track

This seems like a Carbon bug to me.

From: Bryan Prusha [mailto:email@hidden]
Sent: Tuesday, October 23, 2007 7:47 PM
To: Yaron Tadmor
Cc: email@hidden
Subject: Re: drag manager strange behavior

Does the DragRef have the same value for both sets of receive calls? Perhaps a second drag is being accidentally created after the first drop. It would be interesting if you could identify the full backtraces for the receive calls.

On Oct 23, 2007, at 10:05 AM, Yaron Tadmor wrote:

Hi,

I installed a track and a receive handler for drag and drop support.

The track handler simply redraws some part of the window to let the user know where the drag is going to fall, and returns noErr.

The receive handler loads the image from a file that was dragged and adds it to the window, then returns noErr (an error is returned if it’s not an image file).

In most situations the drag works perfectly fine.

However, when the track handler takes a little more time, a strange thing happens. My receive handler gets called twice!

Tracing the code I added printouts in both track and receive handlers start and end, and I get the following print:

…

enter track

end track

enter track

end track

enter receive

end receive

enter track

end track

enter track

end track

enter receive

end receive

enter track

end track

enter track

end track

I’m not really sure what is going on, but it seems like when the release happens while in the track functions, I get 2 calls to receive.

Is this a known issue? Has anyone seen this?

Thanx

Yaron Tadmor

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