Pointer grabs causing accessibility issues! Why not deprecate them?

Daniel Stone daniel at fooishbar.org
Mon Apr 28 05:38:37 PDT 2008

On Mon, Apr 28, 2008 at 02:23:48PM +0200, Francesco Fumanti wrote:
> Daniel Stone wrote:
>  >> In fact, the purpose of this email is to make the xorg developer
>  >> aware of the issue and ask them to consider whether deprecating
>  >> the pointer grabbing functionality from the X server would make
>  >> any sense and be feasible?
>  >
>  > It would not be at all feasible.
> Could you please expand on the main reasons why it is not feasible?
> For example, in what situations are the pointer grabs really unavoidable 
> and unreplacable by other techniques?

Which other techniques? Right now, pointer grabs are used for drag and
drop, popup menus, selection of other windows (e.g. when taking a
screenshot in the GIMP), and also confining the pointer to certain
bounds, as well as in security-sensitive applications such as
screensavers and lock dialogs.  Oh, and all keyboard shortcuts and mouse
actions (e.g. Alt-drag in your window manager).

> Matthew Garrett wrote:
>  > Accessibility is a
>  > difficult field, and it's not practical to ask every application
>  > developer to support every possible accessible input method in their
>  > dialogs - what would you do for people who want to use Dasher rather
>  > than an on-screen keyboard, for instance?
> That is what I had in mind: if possible, would it not be better to try 
> to solve the problem at the source, instead of passing the issues to the 
> application developers!?

Grabs are hard, but X's input model is really quite fundamentally based
on them, so getting rid of them would be next to impossible.  It's not
really worth discussing without any mention of the alternate solutions,
and so far there haven't really been any.

Anyway, the PolicyKit people want to prevent people from typing their
password into another, untrusted application (it could just be skimming
the password and then moving it on to the PolicyKit dialog box, hence
the concern).  If it's in-process, then the process can and should take
care of these issues.  If it's out-of-process, then they need to work
out how to trust out-of-process windows.  Neither of these problems are
solved by eliminating grabs.

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