[Bug 145956] New: Kompare displays wrong line numbers in target file after applying a change

[Olivier Vitrat]

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http://bugs.kde.org/show_bug.cgi?id=145956         
           Summary: Kompare displays wrong line numbers in target file after
                    applying a change
           Product: kompare
           Version: unspecified
          Platform: Debian stable
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: kompare-devel kde org
        ReportedBy: ovit.debian gmail com


Version:            (using KDE KDE 3.5.5)
Installed from:    Debian stable Packages

Reported in Debian BTS at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=364881

Create two example files to reproduce the bug:

a.txt:

1a
2a
- new line inserted here -
- new line inserted here -
- new line inserted here -
- new line inserted here -
3a
4a
5a - modified -
6a - modified -
7a - modified -
8a

b.txt:

1a
2a
3a
4a
5a
6a
7a
8a

Then compare them: kompare a.txt b.txt
Apply the first difference (inserted lines).
Line numbers will be wrong in the target file.
Apply the second difference (modified lines).
Line numbers of modified lines will be copied
from the source file (a.txt). This behaviour
causes very strange line numbering in the target
file.

This bug is usually harmless, but causes problems
when you try to remember positions by target line
numbers to be able to do changes later. You will
easily write down wrong line numbers and will not
be able to locate these positions in the merged
target file in the source code editor later.
This is especially flustrating when merging fixes
between code bases of similar applications.

In my opinion, kompare should renumber target lines
after applying each difference from the source file
and ensure that line numbers are continuous as usual.
The difference graphics will show the source of such
lines, so copying source line numbers is rather a
wrong idea than a feature.