Re: master 2021835326 2/3: Implement `return-frame' for DND on NS

Re: master 2021835326 2/3: Implement `return-frame' for DND on NS

[Po Lu]

Po Lu via Mailing list for Emacs changes <emacs-diffs@gnu.org> writes:

> +#ifdef NS_IMPL_COCOA
> +- (void) draggedImage: (NSImage *) dragged_image
> +	      movedTo: (NSPoint) screen_point
> +{
> +  NSInteger window_number;
> +  NSWindow *w;
> +
> +  if (dnd_mode == RETURN_FRAME_NEVER)
> +    return;
> +
> +  window_number = [NSWindow windowNumberAtPoint: [NSEvent mouseLocation]
> +		    belowWindowWithWindowNumber: 0];
> +  w = [NSApp windowWithWindowNumber: window_number];
> +
> +  if (!w || w != self)
> +    dnd_mode = RETURN_FRAME_NOW;
> +
> +  if (dnd_mode != RETURN_FRAME_NOW
> +      || ![[w delegate] isKindOfClass: [EmacsView class]])
> +    return;
> +
> +  dnd_return_frame = ((EmacsView *) [w delegate])->emacsframe;
> +
> +  /* FIXME: there must be a better way to leave the event loop.  */
> +  [NSException raise: @""
> +	      format: @"Must return DND frame"];
> +}
> +#endif

This works (and there's nothing in the documentation forbidding it), but
prints an ugly warning message to stdout every time the exception is
raised.  Does anyone know of a better way to stop an NS drag-and-drop
operation inside one of the drag source callbacks?

Re: master 2021835326 2/3: Implement `return-frame' for DND on NS

[YAMAMOTO Mitsuharu]

On Tue, 31 May 2022 22:07:23 +0900,
Po Lu wrote:
> 
> > +  /* FIXME: there must be a better way to leave the event loop.  */
> > +  [NSException raise: @""
> > +	      format: @"Must return DND frame"];
> > +}
> > +#endif
> 
> This works (and there's nothing in the documentation forbidding it), but
> prints an ugly warning message to stdout every time the exception is
> raised.  Does anyone know of a better way to stop an NS drag-and-drop
> operation inside one of the drag source callbacks?

Posting ESC KeyDown event seems to work, as long as I tested with
Emacs 29-based Mac port (in development).

BTW, I think safe_call/redisplay in -[EmacsView draggingUpdated:] is
unsafe in some situations.  This method is called from the main thread
in the context of `select' emulation if the dragging is originated
from another application.  Because `thread_select' may cause thread
switching if we have multiple Lisp threads, Lisp evaluation in another
thread might be in progress while the main thread is waiting for the
completion of the `select' emulation.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp

Re: master 2021835326 2/3: Implement `return-frame' for DND on NS

[Po Lu]

YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp> writes:

> Posting ESC KeyDown event seems to work, as long as I tested with
> Emacs 29-based Mac port (in development).

Thank you.  I am not quite sure how to do that, could you please explain
how?

> BTW, I think safe_call/redisplay in -[EmacsView draggingUpdated:] is
> unsafe in some situations.  This method is called from the main thread
> in the context of `select' emulation if the dragging is originated
> from another application.  Because `thread_select' may cause thread
> switching if we have multiple Lisp threads, Lisp evaluation in another
> thread might be in progress while the main thread is waiting for the
> completion of the `select' emulation.

Could you please suggest a fix?