Bug 13808

Summary: mouse sensitivity setting (for acceleration disabled)
Product: xorg Reporter: Javeed Shaikh <syscrash2k>
Component: Server/Input/CoreAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: trivial    
Priority: highest CC: brice.goglin, peter.hutterer
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Patch to fix mouse acceleration none

Description Javeed Shaikh 2007-12-24 10:23:18 UTC 
Older versions of the X server would (implicitly) allow one to do, for example
xset m 1/8 1
to disable mouse acceleration. The '1/8' could be tweaked to change the
mouse sensitivity under these non-accelerated conditions.

In the latest versions of the X server, the code has been (significantly?)
cleaned up. Unfortunately, the above no longer works properly. Try it; the mouse
pointer will not move unless the mouse is moved very rapidly.

It would be nice if there was a (driver-independent?) way to set the mouse
sensitivity.

The old way was consistent, in the sense that
(1) xset m 2 1
doubles the mouse speed but still disables acceleration, and that
(2) xset m 1/8 1
decreases the mouse speed by some amount.

I have no idea how to re-implement the old model. The current code appears to
be correct; it multiplies the mouse delta by 1/8, and for small movements, the
mouse delta can be (1, 1); (1/8)*(1, 1) = (0, 0), and so this results in no
pointer motion.

Can this be "fixed" so that even without acceleration, one can use fractional
values like '1/8' to modify the mouse sensitivity?
Comment 1 Javeed Shaikh 2007-12-24 10:24:43 UTC 
I forgot to mention that (1) still works in the new model. Thus
xset m 2 1
will currently "double" the pointer speed, as expected.
Comment 2 Javeed Shaikh 2007-12-24 11:10:39 UTC 
I believe I have found the source of the issue.
include/inputstr.h:    int                   dxremaind, dyremaind; /* for acceleration */

Those should be floats.
I'm going to recompile and test that, of course...
Comment 3 Javeed Shaikh 2007-12-24 11:40:08 UTC 
Indeed, changing
include/inputstr.h:    int                   dxremaind, dyremaind; /* for
acceleration */
to
include/inputstr.h:    float                   dxremaind, dyremaind; /* for
acceleration */

fixes the issue.
Comment 4 Javeed Shaikh 2008-01-18 15:16:19 UTC 
This seems to be fixed in newer versions.
Comment 5 Javeed Shaikh 2008-01-19 18:29:54 UTC 
False alarm. It's still broken.

I'm not sure what caused me to think that it was fixed.
I swear I saw inputstr.h no longer exist, with the code fixed
in another file or something...

I'll attach a patch in a minute.
Comment 6 Javeed Shaikh 2008-01-19 18:32:07 UTC 
Created attachment 13806 [details] [review]
Patch to fix mouse acceleration
Comment 7 Peter Hutterer 2008-01-22 15:56:43 UTC 
*** Bug 14205 has been marked as a duplicate of this bug. ***
Comment 8 Peter Hutterer 2008-01-22 16:03:57 UTC 
(In reply to comment #6)
> Created an attachment (id=13806) [details]
> Patch to fix mouse acceleration
> 

this patch breaks the ABI, so we can't put it in before 1.5.
Comment 9 Peter Hutterer 2008-06-28 03:43:34 UTC 
Was commited to git master as 0050165a67bb462e0bf644a11644ad9d587c62bb.

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