[Tcl-bugs] [ tktoolkit-Bugs-220935 ] canvas dash update problem

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Bugs item #220935, was opened at 2000-11-01 02:33
Message generated for change (Comment added) made by wangnick
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Category: 05. Canvas Items
Group: obsolete: 8.4a1
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Brent B. Welch (welch)
Assigned to: Jan Nijtmans (nijtmans)
Summary: canvas dash update problem

Initial Comment:
OriginalBugID: 5997 Bug
Version: 8.4a1
SubmitDate: '2000-07-10'
LastModified: 
Severity: MED
Status: UnAssn
Submitter: techsupp
OS: Linux-Red Hat
OSVersion: see below.
Machine: Linux gitarre 2.2.15 #1 Wed May 10 22:58:59 CEST 2000 i686 unkno


Name:
Matthias Jung

Extensions:
none

CustomShell:
no.

Comments:
If other dash pattern styles are specified, e.g. {40 1}, the line IS
    updated. E.g. the above
    error can be worked around by specifying
    
    .c itemconfigure 1 -dash {40 1}
    .c itemconfigure 1 -dash {40 40}

ReproducibleScript:
canvas .c
pack .c
.c create line 1 1 300 200 -dash {15 15}
.c itemconfigure 1 -dash {40 40}

ObservedBehavior:
Line is not updated to the new dash pattern.

DesiredBehavior:
Updated dash pattern.





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Comment By: Sebastian Wangnick (wangnick)
Date: 2007-07-12 17:46

Message:
Logged In: YES 
user_id=202812
Originator: NO

Note that there is another bug hidden in the canvas dash handling
routines:

*   if ((dash->number<-1) || ((dash->number == -1) &&
(dash->pattern.array[1]!=','))) {
	char *q;
	int i = -dash->number;

        p = (i > sizeof(char *)) ? dash->pattern.pt :
dash->pattern.array;
	q = (char *) ckalloc(2*(unsigned int)i);
	i = DashConvert(q, p, i, width);
	XSetDashes(((TkCanvas *)canvas)->display, outline->gc, outline->offset,
q, i);
	ckfree(q);
    } else ...

In the line * above, it should be dash->pattern.array[0]!=','

To provoke the error, create a line item with dash, say, ",,", and then
reconfigure the dash to ".", and note that this will erroneously not change
the pattern (since the second char in the pattern array is still ",").

----------------------------------------------------------------------

Comment By: Sebastian Wangnick (wangnick)
Date: 2007-07-12 17:42

Message:
Logged In: YES 
user_id=202812
Originator: NO

This is because ANY dash setting of the form {n n} is disregarded, and
rather dash 4 is implemented. See tkCanvUtil.c:
*	if (dash->number >= 2) {
*	    gcValues->dashes = 4;
*	} else 
        if (dash->number > 0) {
	    gcValues->dashes = dash->pattern.array[0];
	} else {
	    gcValues->dashes = (char) (4 * width);
	}

and then:
    } else if ( dash->number>2 || (dash->number==2 &&
		(dash->pattern.array[0]!=dash->pattern.array[1]))) {
        p = (char *) (dash->number > sizeof(char *)) ? dash->pattern.pt :
dash->pattern.array;
	XSetDashes(((TkCanvas *)canvas)->display, outline->gc, outline->offset,
p, dash->number);
    }

To fix this problem the lines marked * above must be deleted.

----------------------------------------------------------------------

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