#90 'Add manual diff alignment' scrolls to the first block

[Timbojones]

Repro steps:

1) Open a two-file diff
2) Select some text in A
3) Ctrl-Y
4) Select some text in B
5) Ctrl-Y
6) Scroll down
7) Select some text in A
8) Ctrl-Y

Expected result:
Vertical scrollbar stays where it is, or moves the new alignment block to the top of the view.

Actual result:
Vertical scrollbar moves the first alignment block to the top of the view. Depending on file length, the new alignment block may be far far away, and difficult to find.

[Timbojones]

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Originator: YES

Also:
The horizontal scroll position gets reset to 0. I expect it to stay at the position I scrolled to.

These issues make it difficult to diff e.g. a verbose directory listing where files have been added.

[Wesley J. Landaker]

Here is a quick hack I did on my own copy because this was so incredibly annoying. This isn't perfect, but it's the right idea:

=== modified file 'src-QT4/pdiff.cpp'
--- src-QT4/pdiff.cpp 2009-03-03 22:39:13 +0000
+++ src-QT4/pdiff.cpp 2009-03-03 22:46:27 +0000
@@ -2241,10 +2241,14 @@
m_manualDiffHelpList.push_back( mdhe );
*/

• int saved_vscroll_value = m_pDiffVScrollBar->value();
  +
  insertManualDiffHelp( &m_manualDiffHelpList, winIdx, firstLine, lastLine );

  init( false, 0, false ); // Init without reload
  slotRefresh();
  +
  + m_pDiffVScrollBar->setValue(saved_vscroll_value);
  }
  }