screen redraw problem

screen redraw problem

[J S]

Hi,

I have an application which has some boxes in the window. The window itself 
is scrollable. When I scroll down -  no problem, but when I scroll up the 
boxes turn into long vertical bars. This problem doesn't happen with Exceed, 
but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.

Can anyone advise me whether this is a bug, or is there some setting I need 
to add? Let me know if you need anymore information.

Thanks for any help.

JS.

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Re: screen redraw problem

[J S]

Thanks for the help I got on this from Harold and Alan. The application was 
written in-house and after I asked the client for the source code, they 
managed to find the error themselves. For some reason, this only showed up 
in XFree86 though (not Exceed or Sun X-Windows). Here's what they said:

"An XWindows Draw function was taking a clipping area as a parameter. Under 
Xfree86, depending on what you are doing, invalid clipping areas were being 
generated and so the Draw function was causing screen distortions. I have 
put a validation in which checks the clipping area and if invalid it does 
not paint. In the old days when I used to work on the Windows SDK and 
OS2/Presentation Manager we used to hit similiar problems. This fix appears 
to be working."

>JS,
>
>Can you tell us about the application - is it available anywhere so I
>can take a look too ?
>
>Alan.

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Re: screen redraw problem

[J S]

Hi Alan,

I wish I could. It's a legacy application used by my work called ISIS which 
runs on an old VAX system (not an OS I'm really familiar with). I don't 
think it's written in-house either, so getting the source code is probably a 
no-no too. In fact, the same applies to most X apps we have at my work! I'll 
check it out on Monday though. Thanks for your interest.

JS.


>JS,
>
>Can you tell us about the application - is it available anywhere so I
>can take a look too ?
>
>Alan.

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Re: screen redraw problem

[Alan Hourihane]

JS,

Can you tell us about the application - is it available anywhere so I
can take a look too ?

Alan.

Re: screen redraw problem

[Harold L Hunt II]

JS,

J S wrote:

> Harold,
> 
> Many thanks for email. I have created an XFree debug build now and a 
> symbolic link from /usr/X11R6_suffix/lib/X11/fonts to 
> /usr/X11R6/lib/X11/fonts.

That is a good idea.  I never thought of just creating a symlink.  Doh!

> In order to debug this though, what's the best approach?
> For example, should I use any flags on the xwin command line? Do you use 
> gdb to do the debugging? If so, could you just give me a clue as to 
> where I might want to set the breakpoint given the nature of the problem?

Boy... this is really tough to say.  I think you're going to have to 
look at the client code (to understand what happens when the window is 
scrolled), the Xlib code (to understand what it does when the window is 
scrolled), and the server code (to see whether the requested operation 
is successful and performed correctly).

Actually, a good first start would be some experimentation with your app 
(assuming you have the source and it compiles on Cygwin/X):

1) Compile the app against the Cygwin/X libs and headers.

2) Run the app under XWin.exe (you have done this, I know).

3) Run the app under Exceed (you said you did this too).  At this point, 
it is still linked to our libs, so correct operation would mean the 
problem is in XWin.exe, not in Xlib.

4) If you have access to Solaris machines that are running Sun's X 
Server, recompile the app on them and launch it locally.  Also, launch 
the app through ssh and display it in XWin.exe.  Proper display on 
Solaris when run locally would be interesting.  Proper display in 
XWin.exe would mean that the app is probably using Xlib in a slightly 
broken manner which works for some platforms but not all platforms.  In 
that case, it will be better to fix the app.


The next steps after this are to read the code as I described above and 
figure out where to stick your breakpoint.  I can't really tell you more 
than that since I don't know what functions your code is calling (and I 
don't have your code).

You should be able to figure it out.  Feel free to continue asking 
questions.

Harold

Re: screen redraw problem

[J S]

Harold,

Many thanks for email. I have created an XFree debug build now and a 
symbolic link from /usr/X11R6_suffix/lib/X11/fonts to 
/usr/X11R6/lib/X11/fonts.

In order to debug this though, what's the best approach?
For example, should I use any flags on the xwin command line? Do you use gdb 
to do the debugging? If so, could you just give me a clue as to where I 
might want to set the breakpoint given the nature of the problem?

Sorry to ask for spoon-feeding on this!! Thanks again though.

JS.


>JS,
>
>Start here:
>http://xfree86.cygwin.com/docs/cg/prog-obtaining-source.html
>
>Then read how to compile:
>http://xfree86.cygwin.com/docs/cg/prog-build-native.html
>
>Notice that towards the bottom of the above section it tells how to do a 
>"Standard Build" and a "Debug Build".  The debug build uses the "makeg" 
>script, so you don't have to edit any Imakefiles or config files.
>
>Finally, read how to move your current X installation safely out of the way 
>before installing your local build:
>http://xfree86.cygwin.com/docs/cg/prog-build-native.html#prog-compiling-install
>
>As an absolute last step, if you created a host.def file that said not to 
>build fonts (look at xf86site.def for an example), then you need to cut and 
>paste C:\cygwin\usr\X11R6_suffix\lib\X11\fonts to 
>C:\cygwin\usr\X11R6\lib\X11\fonts.  Cutting and pasting is an instantaneous 
>operation.  Copying the files would take up to an hour, as there are around 
>20,000 font files.  Just be sure that you cut and paste that fonts folder 
>into another folder before you delete one of your test installations.  You 
>don't want to end up deleting that folder... you would be in a world of 
>hurt.
>
>Harold
>
>J S wrote:
>
>>Ha ! OK I'll try to be that guy! What's the best way to do this? Recompile 
>>XWin with the -g flag? Is there anything to change in the Makefile? 
>>Haven't done this before so would appreciate any pointers.
>>
>>Thanks a lot.
>>
>>
>>
>>>JS,
>>>
>>>Looks like you have found a generic problem with X or one of the 
>>>libraries you are using.  It is going to take a lot of debugging... you 
>>>are going to have to be that guy.
>>>
>>>Harold
>>>
>>>J S wrote:
>>>
>>>>Is there anymore information I need to add to this post? I would really 
>>>>like to get some help with it. The logs don't seem to be showing 
>>>>anything. I've tried setting different color depths, and screen 
>>>>resolutions but to no avail.
>>>>
>>>>Hi,
>>>>
>>>>I have an application which has some boxes in the window. The window 
>>>>itself
>>>>is scrollable. When I scroll down -  no problem, but when I scroll up 
>>>>the
>>>>boxes turn into long vertical bars. This problem doesn't happen with 
>>>>Exceed,
>>>>but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.
>>>>
>>>>Can anyone advise me whether this is a bug, or is there some setting I 
>>>>need
>>>>to add? Let me know if you need anymore information.
>>>>
>>>>Thanks for any help.
>>>>
>>>>JS.
>>>>
>>>>_________________________________________________________________
>>>>Stay in touch with absent friends - get MSN Messenger 
>>>>http://www.msn.co.uk/messenger
>>>>
>>>
>>
>>_________________________________________________________________
>>It's fast, it's easy and it's free. Get MSN Messenger today! 
>>http://www.msn.co.uk/messenger
>>
>

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Re: screen redraw problem

[Harold L Hunt II]

JS,

Start here:
http://xfree86.cygwin.com/docs/cg/prog-obtaining-source.html

Then read how to compile:
http://xfree86.cygwin.com/docs/cg/prog-build-native.html

Notice that towards the bottom of the above section it tells how to do a 
"Standard Build" and a "Debug Build".  The debug build uses the "makeg" 
script, so you don't have to edit any Imakefiles or config files.

Finally, read how to move your current X installation safely out of the 
way before installing your local build:
http://xfree86.cygwin.com/docs/cg/prog-build-native.html#prog-compiling-install

As an absolute last step, if you created a host.def file that said not 
to build fonts (look at xf86site.def for an example), then you need to 
cut and paste C:\cygwin\usr\X11R6_suffix\lib\X11\fonts to 
C:\cygwin\usr\X11R6\lib\X11\fonts.  Cutting and pasting is an 
instantaneous operation.  Copying the files would take up to an hour, as 
there are around 20,000 font files.  Just be sure that you cut and paste 
that fonts folder into another folder before you delete one of your test 
installations.  You don't want to end up deleting that folder... you 
would be in a world of hurt.

Harold

J S wrote:

> Ha ! OK I'll try to be that guy! What's the best way to do this? 
> Recompile XWin with the -g flag? Is there anything to change in the 
> Makefile? Haven't done this before so would appreciate any pointers.
> 
> Thanks a lot.
> 
> 
> 
>> JS,
>>
>> Looks like you have found a generic problem with X or one of the 
>> libraries you are using.  It is going to take a lot of debugging... 
>> you are going to have to be that guy.
>>
>> Harold
>>
>> J S wrote:
>>
>>> Is there anymore information I need to add to this post? I would 
>>> really like to get some help with it. The logs don't seem to be 
>>> showing anything. I've tried setting different color depths, and 
>>> screen resolutions but to no avail.
>>>
>>> Hi,
>>>
>>> I have an application which has some boxes in the window. The window 
>>> itself
>>> is scrollable. When I scroll down -  no problem, but when I scroll up 
>>> the
>>> boxes turn into long vertical bars. This problem doesn't happen with 
>>> Exceed,
>>> but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.
>>>
>>> Can anyone advise me whether this is a bug, or is there some setting 
>>> I need
>>> to add? Let me know if you need anymore information.
>>>
>>> Thanks for any help.
>>>
>>> JS.
>>>
>>> _________________________________________________________________
>>> Stay in touch with absent friends - get MSN Messenger 
>>> http://www.msn.co.uk/messenger
>>>
>>
> 
> _________________________________________________________________
> It's fast, it's easy and it's free. Get MSN Messenger today! 
> http://www.msn.co.uk/messenger
> 

Re: screen redraw problem

[J S]

Ha ! OK I'll try to be that guy! What's the best way to do this? Recompile 
XWin with the -g flag? Is there anything to change in the Makefile? Haven't 
done this before so would appreciate any pointers.

Thanks a lot.



>JS,
>
>Looks like you have found a generic problem with X or one of the libraries 
>you are using.  It is going to take a lot of debugging... you are going to 
>have to be that guy.
>
>Harold
>
>J S wrote:
>
>>Is there anymore information I need to add to this post? I would really 
>>like to get some help with it. The logs don't seem to be showing anything. 
>>I've tried setting different color depths, and screen resolutions but to 
>>no avail.
>>
>>Hi,
>>
>>I have an application which has some boxes in the window. The window 
>>itself
>>is scrollable. When I scroll down -  no problem, but when I scroll up the
>>boxes turn into long vertical bars. This problem doesn't happen with 
>>Exceed,
>>but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.
>>
>>Can anyone advise me whether this is a bug, or is there some setting I 
>>need
>>to add? Let me know if you need anymore information.
>>
>>Thanks for any help.
>>
>>JS.
>>
>>_________________________________________________________________
>>Stay in touch with absent friends - get MSN Messenger 
>>http://www.msn.co.uk/messenger
>>
>

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Re: screen redraw problem

[Harold L Hunt II]

JS,

Looks like you have found a generic problem with X or one of the 
libraries you are using.  It is going to take a lot of debugging... you 
are going to have to be that guy.

Harold

J S wrote:

> Is there anymore information I need to add to this post? I would really 
> like to get some help with it. The logs don't seem to be showing 
> anything. I've tried setting different color depths, and screen 
> resolutions but to no avail.
> 
> Hi,
> 
> I have an application which has some boxes in the window. The window itself
> is scrollable. When I scroll down -  no problem, but when I scroll up the
> boxes turn into long vertical bars. This problem doesn't happen with 
> Exceed,
> but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.
> 
> Can anyone advise me whether this is a bug, or is there some setting I need
> to add? Let me know if you need anymore information.
> 
> Thanks for any help.
> 
> JS.
> 
> _________________________________________________________________
> Stay in touch with absent friends - get MSN Messenger 
> http://www.msn.co.uk/messenger
> 

screen redraw problem

[J S]

Is there anymore information I need to add to this post? I would really like 
to get some help with it. The logs don't seem to be showing anything. I've 
tried setting different color depths, and screen resolutions but to no 
avail.

Hi,

I have an application which has some boxes in the window. The window itself
is scrollable. When I scroll down -  no problem, but when I scroll up the
boxes turn into long vertical bars. This problem doesn't happen with Exceed,
but on XFree86 (both Linux XFree86 and Cygwin-XFree) it does.

Can anyone advise me whether this is a bug, or is there some setting I need
to add? Let me know if you need anymore information.

Thanks for any help.

JS.

_________________________________________________________________
Stay in touch with absent friends - get MSN Messenger 
http://www.msn.co.uk/messenger