[Tcl-bugs] [ tktoolkit-Bugs-628863 ] tab incorrect with lmargin1

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Bugs item #628863, was opened at 2002-10-25 22:18
Message generated for change (Comment added) made by tm386
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=112997&aid=628863&group_id=12997

Category: 18. [text]
Group: obsolete: 8.4.1
Status: Open
Resolution: None
Priority: 9
Submitted By: Tao Ma (tm386)
Assigned to: Jeffrey Hobbs (hobbs)
Summary: tab incorrect with lmargin1

Initial Comment:
in the latest 8.4.1 with the following code:

text .text
.text tag configure text -lmargin1 30 -font {Courier 10}
.text insert 1.0 "a\n\tb\tc"
.text tag add text 0.0 end
pack .text

the distance between a,b is not the same as
the distance between b,c. the first tabstop seems
to be caculated wrong, this seems to be caused
by the -lmargin1 parameter, 

the following diff in tkTextDisp.c seems to fix the
problem:
320c320
<                           TkTextDispChunk *chunkPtr));
---
>                           TkTextDispChunk *chunkPtr, int 
tabOrigin));
379c379
<                           int maxX));
---
>                           int maxX, int tabOrigin));
800a801
>     int tabOrigin;
880a882
>     tabOrigin = 0;
958a961
>           tabOrigin = x;
1060c1063
<               AdjustForTab(textPtr, tabArrayPtr, tabIndex, 
tabChunkPtr);
---
>               AdjustForTab(textPtr, tabArrayPtr, tabIndex, 
tabChunkPtr, tabOrigin);
1065c1068
<           tabSize = SizeOfTab(textPtr, tabArrayPtr, 
tabIndex, x, maxX);
---
>           tabSize = SizeOfTab(textPtr, tabArrayPtr, 
tabIndex, x, maxX, tabOrigin);
1131c1134
<       AdjustForTab(textPtr, tabArrayPtr, tabIndex, 
tabChunkPtr);
---
>       AdjustForTab(textPtr, tabArrayPtr, tabIndex, 
tabChunkPtr, tabOrigin);
4823c4826
< AdjustForTab(textPtr, tabArrayPtr, index, chunkPtr)
---
> AdjustForTab(textPtr, tabArrayPtr, index, chunkPtr, 
tabOrigin)
4834a4838
>     int tabOrigin;
4864c4868
<       desired = NextTabStop(textPtr->tkfont, x, 0);
---
>       desired = NextTabStop(textPtr->tkfont, x, 
tabOrigin);
5005c5009
< SizeOfTab(textPtr, tabArrayPtr, index, x, maxX)
---
> SizeOfTab(textPtr, tabArrayPtr, index, x, maxX, 
tabOrigin)
5016a5021
>     int tabOrigin;
5022c5027
<       tabX = NextTabStop(textPtr->tkfont, x, 0);
---
>       tabX = NextTabStop(textPtr->tkfont, x, tabOrigin);




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>Comment By: Tao Ma (tm386)
Date: 2003-11-16 02:54

Message:
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user_id=635724

i dont understand your point of comparing word and tk.

yes you can use -tabs to align at a absolute pixel value.
but wihtout these, by default, i think tab should be
measured from the possible start of the 1st character.
this is just my personal opinon. like you said if you just 
define tab to be always measured from pixel 0 then you 
are right there is no problem at all.


 

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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-16 00:24

Message:
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I've yet to see any editor which does what you describe
(even Microsoft Word does as Tk does).  So when you say
'very natural' to you, that is hardly a "compelling
argument" for a particular behaviour.

IMHO, If you want to align things at tabs, use tabs stops --
that's what they're for.  Using 'lmargin1' is really for
indenting the first line of a paragraph for cosmetic purposes.

Finally, the purpose of tab stops is to align at the 'stops'
you specify, _not_ necessarily at equal intervals.  You can
place those stops wherever you like, and stops are, in
general, relative to the page, not to the current indent
level -- precisely to achieve the goal you are looking for
-- to enable consistent alignment. 

It seems you ought therefore to use '.text configure -tabs'
to achieve the effect you want.




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Comment By: Tao Ma (tm386)
Date: 2003-11-16 00:04

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it seems very natural to assume that tab will start
at lmargin. 

the purpose for using tab is to allign text at equal 
intervals now the use of lmargin has broken this.


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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-15 12:52

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The reporter seems to be assuming that tab stops should be
relative to lmargin1, rather than relative to the left edge
(x=0) of the widget. There is no mention of this sort of
'floating ruler' behaviour in the text widget man pages, so
I think it is really a case of misreading the documentation.

I do agree, however, that the documentation should be made
clearer on this point.

Unless I hear compelling arguments to the contrary, I'll set
about improving the documentation and then mark this as invalid.

Any comments, please?



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Comment By: Vince Darley (vincentdarley)
Date: 2003-11-12 17:52

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I'm not sure I understand what the desired behaviour is
here. I get what I would expect:

    a
          b         c

can anyone explain?


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Comment By: Donal K. Fellows (dkf)
Date: 2003-02-25 10:38

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I agree that there's work to be done in the future on
several aspects of the behaviour of tabs (Tk's default
behaviour is deeply magical, which is not good) and this
could be fixed at the same time.

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Comment By: Jeffrey Hobbs (hobbs)
Date: 2003-02-25 01:20

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Attached is a diff -u version of the patch I made, but I'm letting 
this slip to 8.5 because of the visual difference.  I think it is 
right, but I'd like to see a test, as well as define what happens 
when people fiddle with the -tabs options globally and at the 
tag level.  BTW, the simpler visual example is:

pack [text .text -font {Courier 10}]
.text tag configure margin -lmargin1 30
.text insert 1.0 "a\n\tb\tc" margin


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Comment By: Donal K. Fellows (dkf)
Date: 2003-02-25 00:22

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For future reference, unified or context diffs are easier to
review quickly...
(Patch looks possible; hard to tell without applying it.)

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