Hello,
earlier this day I posted a mail with a list of bugs that I think should
be fixed before we close 3.7. For one of these bugs, no fix has
been proposed so far.

I am therefore really happy to offer a problem analysis and a fix for
the bug that is registered under BFAV archive ID 14350,
posted at Nov 26, 2003.
For quite a time, I was only able to hack around a problem that I did
not understand, but now I think I have found was goes wrong.
Here is the bug description again:
( from the cited bug report)

>In an MVC project, open a file list and select a text file.
>Place the cursor into the text view (at the beginning of the text)
>and scroll down with the down arrow.
>When you reach the end of the text, you will get a notifier
>with the message as soon as you release the 'arrow down' key:

>MessageNotUnderstood: UndefinedObject>>first

>This comes from
>ParagraphEditor>>sameColumn:newLine:forward:,


And here is an analysis of the bug:

In method

ParagraphEditor>>sameColumn: start newLine: lineBlock forward: isForward

we read:


 targetLineNumber _ ((lineBlock value: currentLineNumber) max: 1)
                                min: lines size.

where lines is a temporary variable of the method. Under some
circumstances, the method  fetches the lines from the paragraph
that is edited. (The paragraph is an instance of Paragraph in
MVC and an instance of NewParagraph in Morphic)
Under different circumstances, sameColumn:lineBlock:forward:
computes an array of lines (this is done by ParagraphEditor>>lines).


In NewParagraph, 'lines' is used under an exact fit policy:
For a paragraph that is composed to be displayed in  n
lines, the size of the array is  n .

In a Paragraph, 'lines' is an array of TextLineIntervals.
In Paragraph, the array 'lines' is used under a "keep
additional space" policy and the correct number of lines
is stored in instance variable 'lastLine' and can be
accessed with the method Paragraph>>numberOfLines

When sameColumn:lineBlock:forward:  computes an array
of lines, it can use 'lines size' to obtain the number of lines, but
when it uses the lines from the paragraph, it has to use
'paragraph numberOfLines' to obtain the number of lines.

Solution:

To handle both cases, I use an additional instance variable
to keep the number of lines.

I would be glad to see this fix in the final 3.7 (if that is
still possible), so can some fellow with an interest in
MVC please review my proposal? 

Thank you a lot!
Boris
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