[xmonad] Patch: fix focus when user is moving the mouse

[Spencer Janssen]

On Wed, Apr 09, 2008 at 02:13:39PM -0500, Klaus Weidner wrote:
> Hello,
> 
> the attached patch fixes an issue that had been bugging me - in
> focus-follows-mouse mode, the input focus sometimes lagged behind the
> mouse pointer, and as a result I was closing or typing into the wrong
> window.
> 
> Let me know in case there's a better way to approach this, I'm still new
> to haskell and xmonad.
> 
> I'll send a related patch to the UpdatePointer contrib module separately.
> 
> -Klaus
> 
> Remember if focus changes were caused by mouse actions or by key commands.
>  
>  If the user used the mouse to change window focus (moving into or clicking on a
>  window), this should be handled differently than focus changes due to keyboard
>  commands. Specifically, it's inappropriate to discard window enter/leave events
>  while the mouse is moving. This fixes the bug where a fast mouse motion across
>  multiple windows resulted in the wrong window keeping focus.
>  
>  It's also helpful information for contrib modules such as UpdatePointer - it's
>  supposed to move the mouse pointer only in response to keyboard actions, not if
>  the user was moving the mouse.

First, a minor nitpick: if you want this patch to be applied, please change all
identifiers to camelCase for consistency with the rest of xmonad.

I foresee some problems with this patch.  Consider the following sequence of
events, starting from an empty workspace in the Tall layout:

 - increment nmaster to three
 - create three xterms
 - focus the second window with the mouse.  At this time mouse_focus
   will be set to True
 - position the mouse such that it occupies the upper half of the second window
 - close the second window without using an xmonad keybinding (typing 'exit' in
   an xterm will suffice)
 - the windows will shuffle about, and xmonad will set focus to the last window
   as usual.  Also, the first window will now be under the mouse pointer, and
   an entry event will be generated.

In the old system, this entry event is removed and all is well.  With your
proposed changes the entry event will not be removed, and focus will be changed
to the first window -- not good!


Cheers,
Spencer Janssen