[ubuntu-uk] Mouse accessibility problem

Jim Price d1version at hotmail.com
Tue Apr 10 12:25:42 UTC 2018

Discussion inline - see below:

On 09/04/18 21:06, J Fernyhough wrote:
> On 09/04/18 17:50, Jim Price wrote:
>> Getting the mouse button down and up in a short
>> time is as difficult as getting a reliable double click it would seem.
> After doing some more digging the libinput "DragLockButtons" option may
> help with this:

Thanks, will investigate.

> http://manpages.ubuntu.com/manpages/xenial/man4/libinput.4.html

The "TappingDrag" setting might be worth looking at too. The overall 
problem is similar to the problem some people have with using 
tap-to-click on touchpads, but this setting enables dragging to be 
disabled between button-down and button-up, if I understand it correctly.

> However, it also seems as though you're trying to address
> mutually-exclusive issues. On the one hand, you want to allow a
> single-click-then-move to trigger drag-and-drop behaviour, while at the
> same time you want to prevent a single-click-and-move from triggering
> drag-and-drop behaviour.

Maybe I didn't explain it very well. The idea is to eliminate 
drag-and-drop altogether in the case of a single click. Normally the 
drag would occur between button-down and button-up, and the user pretty 
much can't avoid dragging between button-down and button-up. With double 
clicks (assuming the first single click worked), the interval between 
the first click and the end of the second click unavoidably includes 
movement, which causes all kinds of unwanted behaviour. Again, disabling 
movement in the double click timeout period would at least allow a 
double click to be executed in the same place, albeit at the expense of 
jettisoning drag-n-drop.

> The only way to address this is to separate cursor movement from
> clicking and so allow independent control over both activities. This can
> not be accomplished with a single mouse - you either need to look again
> at larger trackballs (with a central ball, Expert or Orbit-style), or
> some other input device, for example a trackpad, trackpoint/joystick,
> dedicated "click" key/button, or breath controller.

I'd still like to try the disabling of all dragging and dropping by 
disabling movement during a double click timeout, as many desktops can 
be operated without drag and drop altogether. I have not ruled out other 
hardware solutions, but the trackballs and trackpads tried so far have 
not worked out. The trackpad was the most promising, but getting hold of 
a suitably large trackpad has proven difficult. There have been some 
fairly large ones made, but the best looking candidates have been 
discontinued (thanks Logitec). A graphics tablet would be large enough, 
so that might be another possibility.


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