Re: issue with line break option PANGO_WRAP_CHAR

[Behdad Esfahbod <behdad behdad org>]

Thanks.  Please file a bug at bugzilla.gnome.org and attack the patch so we
don't lose this.

behdad

On 13-09-10 08:51 AM, Parth Kanungo wrote:
> Hello Behdad,
>
>  
>
> Thanks for your inputs.
>
>  
>
> I have fixed the issue by adding the a few lines of code (additional code,
> colored in blue) in the *process_item()* function of *pango_layout.c*
>
> I have tested this in English only and it works fine.
>
>  
>
> _Issue_
>
> When space is encountered at the end of the current line and it cannot be
> accommodated there,
>
> the word breaks at the previous glyph.
>
> This is because break_num_chars does not count the current glyph (i.e. space)
>
>  
>
> _Proposed Solution_
>
> In case of above scenario, increase the value of break_num_chars by 1.
>
> And also take into account the break_width.
>
>  
>
> _Modification in code_
>
> __ 
>
>     retry_break:
>
>       /* See how much of the item we can stuff in the line. */
>       width = 0;
>       for (num_chars = 0; num_chars < item->num_chars; num_chars++)
>  {
>    if (width > state->remaining_width && break_num_chars < item->num_chars)
>      break;
>
>    /* If there are no previous runs we have to take care to grab at least one
> char. */
>    if (can_break_at (layout, state->start_offset + num_chars,
> retrying_with_char_breaks) &&
>        (num_chars > 0 || line->runs))
>      {
>        break_num_chars = num_chars;
>        break_width = width;
>      }
>    else
>    {
>     if( (layout->log_attrs[state->start_offset + num_chars].is_white) &&
>       (layout->wrap == PANGO_WRAP_CHAR || layout->wrap == PANGO_WRAP_WORD_CHAR) )
>     {
>      break_num_chars = num_chars + 1;
>      break_width = width + state->log_widths[state->log_widths_offset +
> num_chars];
>     }
>    }
>
>    width += state->log_widths[state->log_widths_offset + num_chars];
>  }
>
> //
>
>  
>
> ------
>
>  
>
> Do you think that this would work fine in other languages also ?
>
>  
>
> Thanks and regards,
>
> Parth Kanungo
>
>  
>
> ------- *Original Message* -------
>
> *Sender* : Behdad Esfahbod<behdad behdad org>
>
> *Date* : Sep 09, 2013 21:44 (GMT+05:30)
>
> *Title* : Re: issue with line break option PANGO_WRAP_CHAR
>
>  
>
> On 13-09-06 08:22 AM, Parth Kanungo wrote:
> > Hello,
> >
> > I am facing an issue with a line break option - PANGO_WRAP_CHAR.
> >
> > You can see the output (image.bmp)
> >
> > for my code (main.cpp)
> >
> > It is clear that "i" can be rendered on the first line after "Th".
> >
> > However, it is coming on the second line. This is wrong.
> >
> > Is this a known bug?
>
> There's many things going on here:
>
> 1. Unicode line breaking algorithm prohibits breaking before a space.  As such
> we try to fit the space after i in the same line.  Normally, after we break
> line, we zero the width of the final space on the line (see
> pango-layout.c:zero_line_final_space).  We try to account for that when
> deciding where to break, but it's possible that we are messing things up,
>
> 2. When WRAP_CHAR, we still never break before a space, while sometimes that's
> the right thing to do no matter what Unicode says.
>
> In short, that piece of code needs some long overdue love, but I don't know
> anyone with the time and expertise to look into it right now.
>
> behdad
>
> > I further debugged and found that
> >
> > 1. can_break_at() gives false for space character.
> >
> > 2. break_width contains the width of "Th" only, when it should contain the
> > width of "The"
> >
> >  
> >
> > But, I am not sure how to fix this.
> >
> > Moreover, this problem aggravates if we introduce multiple spaces between 2 words.
> >
> >  
> >
> > Any pointers in this direction would be helpful.
> >
> >  
> >
> > Thanks and regards,
> > Parth Kanungo
> >
> >
> >
> > _______________________________________________
> > gtk-i18n-list mailing list
> > gtk-i18n-list gnome org
> > https://mail.gnome.org/mailman/listinfo/gtk-i18n-list
>
> -- 
> behdad
> http://behdad.org/
>
>  

-- 
behdad
http://behdad.org/