_DPSDiscardEvents: FlushEventsMatchingListFromQueue returned error (-50)

General
1

I have a MouseDown Event on a ContainerControl in Xojo Desktop. I wish to drag and drop the ContainerControl around a Window or (window-sized) Canvas.

I can set up the drag ok and even create a drag image of the control and it “appears” to drag.

But, regardless of the return value in this event handler I see the following in the DebugLog …

29-Jul-2015 14:55:30.096 myApp.debug[18506]: _DPSDiscardEvents: FlushEventsMatchingListFromQueue returned error (-50)

Wise thoughts and simple remedies appreciated.

Thx … Ian

2

Perhaps I should add, that following this error the event handling is quite weird. Events that should be caught initially on a control are passed through to the underlying canvas then back up to the control once the canvas has had a go …

3

[quote=203206:@Ian Ramsay]I have a MouseDown Event on a ContainerControl in Xojo Desktop. I wish to drag and drop the ContainerControl around a Window or (window-sized) Canvas.

I can set up the drag ok and even create a drag image of the control and it “appears” to drag.

But, regardless of the return value in this event handler I see the following in the DebugLog …

29-Jul-2015 14:55:30.096 myApp.debug[18506]: _DPSDiscardEvents: FlushEventsMatchingListFromQueue returned error (-50)

Wise thoughts and simple remedies appreciated.

Thx … Ian[/quote]

Mac or Windows ?

It would help greatly to be able to reproduce the error. A sample project would be great.

4

It’s happening on Mac.

A bit hard to extract this block of view code easily to create a sample. The layers of embedded / stacked controls are …

ccListBox ccRectangle (for background colour) ccCanvas (for background shadow) ContainerControl (there is an array of these embededwithin ...) bigCanvas (to enable positioning of all the ContainerControls as a group) mainWindow

  1. MouseDown on ContainerControl logs the above error then drops thru to bigCanvas then fires in ContainerControl.
  2. DragReOrderRows in the ccListBox in any of the ContainerControls works fine.
  3. Dragging a ccListBox cell out of one ContainerControl (DragRow) to another also logs the error and no drop event occurs.

This little bit of evidence may give some clues.

Cheers … Ian

5

I created a new project with a bigCanvas, and placed a CC instance on top.

Indeed if you do not return True in the Container Control MouseDown, the event goes through to the canvas. That is quite normal.

But no error.

Something else in your project must be triggering the issue.

6

Standby for better evidence … I’d best do the same and put together a little controlled experiment as you have to isolate this gremlin.

7

Results of the experiment …

So the _DPSDiscardEvents: FlushEventsMatchingListFromQueue is a reproducible debug log message that is written every time a DRAG OPERATION is initiated from a ListBox. Any drag and any ListBox.

Contrary to my earlier belief, this deeper action doesn’t seem to influence the chain of event operations ( now that I better understand and have coded the correct Boolean responses the various Events ) !

This message occurs on Xojo 2015-2.0 and 2.2 with Mac OS 10.10.4. I cannot find any documentation on this error message but somebody may wish to dig a bit deeper …

8

Its an OS issued log message
Apple’s aware of it
It’s been logged since 2001 as far as I can find

9

:slight_smile: