[Tcl-bugs] [ tktoolkit-Bugs-833627 ] TIP 155 text widget crashes and panics.

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Bugs item #833627, was opened at 2003-10-31 13:43
Message generated for change (Comment added) made by patthoyts
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Category: 18. [text]
Group: 8.5a0
Status: Closed
Resolution: Fixed
Priority: 9
Submitted By: Pat Thoyts (patthoyts)
Assigned to: Vince Darley (vincentdarley)
Summary: TIP 155 text widget crashes and panics.

Initial Comment:
I ran the new TIP 155 text widget with tkchat and it
raised a Tk panic with the message
 "LayoutDLine couldn't place any characters on a line"

This is due to the presence of elided text in the
widget. I am hiding the entry messages and if I have
these to be shown then it doesn't panic.

While trying to produce a minimal example I get a crash
from the following tcl code. (This is Win2k Tcl and Tk
HEAD).

  pack [text .t]
  .t insert 0.0 HELLO
  .t tag configure HIDE -elide 1
  .t tag add HIDE 0.0 end


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>Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-08 21:24

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tkchat seems to be happy with this now. Congratulations!

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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-08 17:22

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Ok, try once more.  I finally think I have this correct.  It
was much more complex than I imagined!


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Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-08 01:05

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The last fix seemed to work, but it eventually happened
again. This time it reduces to:

 package require Tk
 pack [text .txt]

 .txt tag configure WELCOME -elide 1
 .txt tag configure SYSTEM -elide 0
 .txt tag configure TRAFFIC -elide 1

 .txt insert end "\n" {SYSTEM TRAFFIC}
 .txt insert end "\n" WELCOME

If the SYSTEM tag is defined after the TRAFFIC tag then the
panic doesn't occur. Also it seems all three tags are
required and both of the insert commands.


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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-07 12:08

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Ok, applied one more fix, solving the latest neat example! 
This fix seems to address a more general issue than the
previous fixes, so could perhaps solve all the tkchat problems.



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Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-05 22:59

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As of tkTextDisp.c rev. 1.22 the problems below are ok, but
the following code will produce the panic.

 package require Tk
 pack [text .txt]
 .txt tag configure SYSTEM -elide 0
 .txt tag configure TRAFFIC -elide 1
 .txt insert end "\n" {SYSTEM TRAFFIC}

I noticed that the order of the two tags is important. It
works fine if the second tag is -elide 0.

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Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-05 15:01

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It looks like we require two elided tags to make this fail
and the newlines. (very slightly simpler):

 package require Tk
 pack [text .txt]
 .txt tag config WELCOME -elide 1
 .txt tag config HELP -elide 1
 .txt insert end "test\n" WELCOME
 .txt insert end "test\n" HELP


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Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-05 14:55

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That was a great suggestion. I have trimmed down the log
results and the final failing set of commands is:

 package require Tk
 pack [text .txt]
 .txt tag config WELCOME -elide 1
 .txt tag config HELP -elide 1
 .txt insert end "\n" {WELCOME NICK}
 .txt insert end "\n" {HELP NICK}


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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-05 08:50

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Can you try to use:

set logfile [open textlog w]
trace add execution .textwidget after log
proc log {args} { puts $::logfile $args }

or something like that to trace the set of tkchat text
widget actions to produce at least an example that doesn't
require a whole application?


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Comment By: Pat Thoyts (patthoyts)
Date: 2003-11-04 23:30

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Sorry. Re-opened because the fault is still present.

I have been unable to produce a minimal demonstration, but
it's easy enough to produce with tkchat.

You need to have tkchat configured with the various system
messages hidden (esp. the Welcome messages). Then when you
connect and it fetches the messages file (not the history,
just the current active chat)  then it panics when it comes
across a message to be hidden.

You will need a chat login to do this, although the chat
data can be obtained from http://mini.net/tchat/messages and
this could be piped into the tkchat app -- however, it is
probably simpler just to use it as-is.

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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-03 16:14

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Ok, fixed the panic too.


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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-03 10:27

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I tried to source tkchat into wish and didn't get a crash. 
Note, however, that I've never used tkchat, have no
'id/password' or anything.  If you can post exact
instructions for how to reproduce from that situation, I can
try to debug...


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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-02 22:13

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I've checked this patch in, then, but can you provide a test
case for the 'panic', please?


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Comment By: Pat Thoyts (patthoyts)
Date: 2003-10-31 22:24

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Your patch here fixes the crash for this code sample but I
still get a panic when starting tkchat in LayoutDLine.

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Comment By: Vince Darley (vincentdarley)
Date: 2003-10-31 14:06

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I see a crash with this example (thanks for such a quick
example!), but it's different to what you get (no panic,
just a segfault).  I can fix this by changing the first few
lines of DlineIndexOfX (in tkTextDisp.c) to:

    TextDInfo *dInfoPtr = textPtr->dInfoPtr;
    register TkTextDispChunk *chunkPtr;

    /*
     * Scan through the line's chunks to find the one that
contains
     * the desired x-coordinate.  Before doing this,
translate the
     * x-coordinate from the coordinate system of the window
to the
     * coordinate system of the line (to take account of
x-scrolling).
     */

    *indexPtr = dlPtr->index;
    x = x - dInfoPtr->x + dInfoPtr->curXPixelOffset;
    chunkPtr = dlPtr->chunkPtr;

    if (chunkPtr == NULL) {
	/* 
	 * This may occur if everything is elided
	 */
	return;
    }

    for (; x >= (chunkPtr->x + chunkPtr->width);

Can you test this please?


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