I would use #mouse to match the internal send names like #notein, etc. :)

Actually, you can receive messages to [notein] using [r #notein] so I could imagine a similar set of mouse objects which work in the same manner ala [mouseup], [mousedown], [mousemove], & possibly [mousedrag]. We can look into the code on those objects and replicate how they work to avoid the missing receiver name.

Honestly, this should be something built in however I would first make sure there isn't any sort of major performance penalty (probably not). Chris's comment about "in 2019" is spot on...

On Mar 15, 2019, at 11:06 AM, pd-list-request@lists.iem.at wrote:

From: Jean-Yves Gratius <jyg@gumo.fr>
To: pd-list@lists.iem.at
Subject: Re: [PD] In 2019 is there a way to detect mouse down/up?
Message-ID: <cc397066-5e73-1e69-5c7e-d55713c4d275@gumo.fr>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

Not sure it can be considered as a vanilla solution, but you should edit 
tcl/pdtk_canvas.tcl file and add one line in the proc 
pdtk_canvas_mouseup (line 216) :

proc pdtk_canvas_mouseup {tkcanvas x y b} {
    set mytoplevel [winfo toplevel $tkcanvas]
    pdsend "$mytoplevel mouseup [$tkcanvas canvasx $x] [$tkcanvas 
canvasy $y] $b"
    pdsend "MOUSE mouseup [$tkcanvas canvasx $x] [$tkcanvas canvasy $y] $b"
}
(see attachment)

Then you'll always need to have a receiver (named "MOUSE") in your 
patch, else you will receive error messages in pd console.
If you click on a bang object in your patch, you can then listen to the 
MOUSE receiver and wait for the message "mouseup"

--------
Dan Wilcox
@danomatika
danomatika.com
robotcowboy.com