Subject: FVWM: FvwmPager goes crazy?

From: Gert Brinkmann <[email-masked]>
Date: Sun, 02 Feb 2003 22:33:24 +0100

Hello,

while experimenting with fvwm i have found a funny thing:

I do have an empty .fvwm2rc file (0 bytes of size) for my fvwm 2.5.5. 
Now i do the following things:

Choose "Issue FVWM Commands" from the default menu.
Enter the following 2 lines:

   Module FvwmPager
   Style FvwmPager sticky

Open up an xterm on each page.

Use the right mouse button to scroll around the screen in the 3x3 Pager
of Desk 0.

The Result is not as expected (The screen should exactly follow the
mouse). Instead the screen drives around in circles and bezier-like
curves even if i move the mouse on a linear way. The faster i move the
mouse, the more crazy the pager becomes.

Sometimes this does not happen right from the start but i have to click 
on the xterm windows before and play with the pager a little bit.

What can this be?

Thanks,

Gert

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From: Marcus Lundblad <[email-masked]>
Date: Sun, 2 Feb 2003 22:42:54 +0100 (CET)

> mouse, the more crazy the pager becomes.

Is mouse acceleration enabled?
Maybe this could be the cause the movement isn't even.

//Marcus

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From: Gert Brinkmann <[email-masked]>
Date: Sat, 08 Feb 2003 14:14:52 +0100

> Maybe this could be the cause the movement isn't even.

"xset q" tells me

Pointer Control:
   acceleration:  2/1    threshold:  4

but i think this is not the problem. The movement is not only un-even. 
The grey box that displays the screen-location in the pager moves around 
in circles and other none-linear moving-paths even if i move the 
mouse-cursor linear. Strange.

Is nobody able to reproduce this?

Gert

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From: Dan Espen <[email-masked]>
Date: Sat, 08 Feb 2003 14:27:23 -0500

> Is nobody able to reproduce this?

I think I figured out what you are talking about, but I don't see
a problem.

I'm not sure I  can move a mouse in  a perfectly linear way (always at
right angles).  So maybe I'm not appreciating some subtlety of
whats happening.

On my system, Fvwm lags behind the mouse (as I think it would be
expected to) and I think X is throwing away some of the X traffic
which might be what you are seeing.

Fvwm doesn't attempt to keep the screen updating synchonous, and
you wouldn't like it if it did.  The effect would probably be a lot
worse.

If you think I'm missing something, or this is causing a problem,
feel free to provide more details.

-- 
Dan Espen                           E-mail: [email-masked]

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From: Gert Brinkmann <[email-masked]>
Date: Mon, 10 Feb 2003 14:07:17 +0100

Dan Espen wrote:

Thank you, for your answer.

> which might be what you are seeing.

Hmm, as i understand you, this would result in a slightly 
stottering/uneven moving of the grey screen-box, but it still follows 
the way of the mouse correctly.

> feel free to provide more details.

It is hard to describe this in english, but i try to describe how i move 
the mouse and how the screen is moving:

I number the desktop pages as follows:

0 3 6
1 4 7
2 5 8

I e.g. start the mouse movement in page 8 and move it in a normal speed 
on a linear way to page 0. This takes approx. about 1 second, i guess, 
maybe 1,5.

At the beginning the grey screen box (i call it "the screen" from now 
on, because the whole screen moves the same way as the screen-box of the 
pager) lays under the mouse cursor on page 8. It starts moving into the 
correct direction and in the beginning follows the mouse. This may be a 
little stottering and uneven but the screen does keep the correct direction.

Approx. when entering page 4, the screen starts moving in small circles 
around the still linear moving mouse cursor (mostly clockwise). At the 
end of page 4 the screen rotates through the pages 0,3,6,7,8,5,2,1, etc. 
and sometimes stucks in an edge-page. Sometimes the movement of the 
screen is not circular, but it moves to the left and right in a 
direction of 90 degrees to the mouse movement.

Well, i could try to draw a small png image that displays an example of 
the movement and post it here if i am allowed.

Somewhere in the fvwm-docs i have read that you should not start a 
module using "Module", but add it to the start-function. Can the 
starting of FvwmPager with "Module" be the problem?

Thanks,

Gert

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From: Dan Espen <[email-masked]>
Date: Mon, 10 Feb 2003 08:38:52 -0500

> the movement and post it here if i am allowed.

No need, using these instructions, I see it now.

> starting of FvwmPager with "Module" be the problem?

Nope.

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From: Gert Brinkmann <[email-masked]>
Date: Fri, 14 Feb 2003 21:57:38 +0100

> No need, using these instructions, I see it now.

Great. So is there a chance for a soon fix? Or do i have to submit this 
issue into an bug tracker of fvwm before?

Ciao,

Gert

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From: Dan Espen <[email-masked]>
Date: Sat, 15 Feb 2003 21:58:45 -0500

> issue into an bug tracker of fvwm before?

I've committed a fix for this in the 2.5.x branch.
Let me know if you can test it.
If the fix seems OK, I'll put it in the 2.4.x branch too.

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From: Gert Brinkmann <[email-masked]>
Date: Mon, 17 Feb 2003 15:46:50 +0100

> I've committed a fix for this in the 2.5.x branch.

If have tested the todays CVS version which includes:

2003-02-16  Dan Espen  <[email-masked]>

* FvwmPager/x_pager.c (DispatchEvent): Fix compilation problems...

Well, the pager's behaviour is different than before, but still not 
correct. With the current version the screen does move into the same 
direction as the mouse does, but you have to move the mouse just a few 
pixels to move the screen all over the pager. So the screen does move 
much faster than the mouse pointer. It feels a little bit like an 
accelerated screen. It is very difficult to handle this.

(I hope there is nothing wrong with my fvwm installation, because i did 
not know how to install the CVS version on my debian machine correctly: 
First i did remove my own fvwm-2.5.5-package that i had installed using 
the tool 'checkinstall'. After this i again used checkinstall to install 
the CVS version.)

Gert

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From: Dan Espen <[email-masked]>
Date: Mon, 17 Feb 2003 09:59:11 -0500

> the tool 'checkinstall'. After this i again used checkinstall to install 

Thanks for the feedback.
I think your install is OK.
I'll look again.

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From: Dan Espen <[email-masked]>
Date: Mon, 17 Feb 2003 11:37:34 -0500

> accelerated screen. It is very difficult to handle this.

Thanks for the description.  It led me right to the problem.
It seems to work pretty well for me now.
If you have the time, try it out and let us know if you see
anything else.

Thanks.