[xmonad] darcs patch: quick hack to avoid infinite (but breakable) loop when...

Sat May 17 06:12:49 EDT 2008

Hello, 

thanks David for taking care of this - I'm currently away from my xmonad
system and can't try to reproduce it, but your change should fix the loop. 

Is something like the following happening?

a) click on tab causes window B to be focused (with mouseFocused true)

b) mouse moves down into old window A, queueing an enter event for A

c) xmonad maps window B, appearing under the mouse pointer

d) enter event for B gets queued

e) xmonad handles enter event for A, causing it to be focused

f) xmonad maps window A, appearing under the mouse pointer

g) enter event for B gets queued

... goto (c)

The problem with my patch would then be that it keeps mouseFocused on for
all these enter events for passing to updatePointer and also uses that
same flag to decide not to clear the pending crossing events, which is
wrong.

The unpatched behaviour restored by your patch is to clear the step (b)
enter event. However, that does the wrong thing if moving the mouse
quickly across multiple windows A-B-C, in that case B keeps the focus
even though the mouse ended in window C.

Probably the right thing to do would be to clear the pending crossing
events in 'windows' whenever the layout manipulation moves/resizes/remaps
windows, and not clear it if only the focus has changed. What would be
a clean way to make that distinction?

-Klaus

On Fri, May 16, 2008 at 04:13:57PM -0400, David Roundy wrote:
> Here's a patch to core to fix a recent regression in xmonad.  Well, maybe
> it's not so recent, but I've only recently upgraded my xmonad to the latest
> darcs version.  It's a crude fix that leaves in place the whole
> isMouseFocused infrastructure and just disables its effect.  Without this
> patch, tabbed is not entirely unuseable, but requires that I train myself
> to hold the mouse very still while selecting tabs.  I'd rather just have
> the old pleasant behavior where I can select even firefox windows without
> waiting before letting my mouse drift and without annoying flashing
> effects.
> 
> David
> 
> Fri May 16 15:09:47 CDT 2008  David Roundy <droundy at darcs.net>
>   * quick hack to avoid infinite (but breakable) loop when using Tabbed.
>   
>   The isMouseFocused hack introduced a race condition where if you click on a
>   tab to select a window, and then move the mouse down before the new window
>   is selected, the focus will alternate between the previously-focused and
>   newly-focused windows in an infinite loop.  This loop can be broken by
>   moving the mouse up to the tab area, but it's pretty unpleasant.  This race
>   condition is easily triggered on my laptop (and presumably on any older
>   computer running bloated applications like firefox).
>   
>   I've disabled the responsible behavior in a minimal way, since it seems
>   likely that someone may wish to reimplement this behavior, but without the
>   race condition.
> 

Content-Description: A darcs patch for your repository!
> 
> New patches:
> 
> [quick hack to avoid infinite (but breakable) loop when using Tabbed.
> David Roundy <droundy at darcs.net>**20080516200947
>  
>  The isMouseFocused hack introduced a race condition where if you click on a
>  tab to select a window, and then move the mouse down before the new window
>  is selected, the focus will alternate between the previously-focused and
>  newly-focused windows in an infinite loop.  This loop can be broken by
>  moving the mouse up to the tab area, but it's pretty unpleasant.  This race
>  condition is easily triggered on my laptop (and presumably on any older
>  computer running bloated applications like firefox).
>  
>  I've disabled the responsible behavior in a minimal way, since it seems
>  likely that someone may wish to reimplement this behavior, but without the
>  race condition.
> ] hunk ./XMonad/Operations.hs 169
>      mapM_ (flip setWMState withdrawnState) (W.allWindows old \\ W.allWindows ws)
>  
>      isMouseFocused <- asks mouseFocused
> -    unless isMouseFocused $ clearEvents enterWindowMask
> +    unless (isMouseFocused && False) $ clearEvents enterWindowMask
>  
>  -- | setWMState.  set the WM_STATE property
>  setWMState :: Window -> Int -> X ()
> 
> Context:
> 
> [add currentTag convenience function
> Devin Mullins <me at twifkak.com>**20080511224258] 
> [Make Mirror a newtype
> Spencer Janssen <sjanssen at cse.unl.edu>**20080508104640] 
> [Comments
> Spencer Janssen <sjanssen at cse.unl.edu>**20080507013122] 
> [Break long line
> Spencer Janssen <sjanssen at cse.unl.edu>**20080507012608] 
> [Style
> Spencer Janssen <sjanssen at cse.unl.edu>**20080507012519] 
> [Simplify
> Spencer Janssen <sjanssen at cse.unl.edu>**20080507011309] 
> [Overhaul Choose, fixes issue 183
> Spencer Janssen <sjanssen at cse.unl.edu>**20080506220809] 
> [Remember if focus changes were caused by mouse actions or by key commands
> Klaus Weidner <kweidner at pobox.com>**20080502175603
>  
>  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.
> ] 
> [Wibble
> Spencer Janssen <sjanssen at cse.unl.edu>**20080506203840] 
> [Added doShift function for more user-friendly hooks
> Ivan N. Veselov <veselov at gmail.com>**20080506185757] 
> [use named colours. fixes startup failure on the XO
> Don Stewart <dons at galois.com>**20080502210149] 
> [Set focus *after* revealing windows
> Spencer Janssen <sjanssen at cse.unl.edu>**20080407222559] 
> [Reveal windows after moving/resizing them.
> Spencer Janssen <sjanssen at cse.unl.edu>**20080407220756
>  This should reduce the number of repaints for newly visible windows.
> ] 
> [Hide newly created but non-visible windows (fixes bug #172)
> Spencer Janssen <sjanssen at cse.unl.edu>**20080430014012] 
> [formatting, eta expansion
> Don Stewart <dons at galois.com>**20080418184337] 
> [XMonad.ManageHook: add 'appName', another name for 'resource'
> Lukas Mai <l.mai at web.de>**20080406012006] 
> [XMonad.ManageHook: make 'title' locale-aware; haddock cleanup
> Lukas Mai <l.mai at web.de>**20080406011338
>  
>  The code for 'title' was stolen from getname.patch (bug #44).
> ] 
> [XMonad.Main: call setlocale on startup
> Lukas Mai <l.mai at web.de>**20080406011234] 
> [floats always use current screen (with less bugs)
> robreim at bobturf.org**20080405135009] 
> [XMonad.Operations: applySizeHint reshuffle
> Lukas Mai <l.mai at web.de>**20080404215615
>  
>  Make applySizeHints take window borders into account. Move old functionality
>  to applySizeHintsContents. Add new mkAdjust function that generates a custom
>  autohinter for a window.
> ] 
> [XMonad.Layout: documentation cleanup
> Lukas Mai <l.mai at web.de>**20080404215444] 
> [Remove gaps from the example config
> Spencer Janssen <sjanssen at cse.unl.edu>**20080329232959] 
> [Remove gaps
> Spencer Janssen <sjanssen at cse.unl.edu>**20080325091526] 
> [TAG 0.7
> Spencer Janssen <sjanssen at cse.unl.edu>**20080329210249] 
> Patch bundle hash:
> f3efdbe61ee5bcdbb219553c7229617caae51b17

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