@Torsten: Can you merge stable to default?  I tried to do so, but there were conflicts during the merge and I don't know the code well enough to choose the correct piece of code to keep for the 3-way merge.

From my tests, the remaining issue is in qscintilla's way to search in selections. Since we already have a workaround for another issue in this case, I decided to drop the use of findFirstInSelection () and handle the search in a given selection by gui's code. The related changeset
http://hg.savannah.gnu.org/hgweb/octave/rev/fbe46901ae62
was pushed to the default branch, since this is a complete redesign of the search & replace in selected text. As a positive side effect, we can drop a configuration test for Qt's abilities.

I leave the report open since I would like to cherry-pick this patch into stable is there are no complains about side effects I was missing during my tests.

With the example from comment #3 I can confirm the issue.

Also the weird effect that replacing A in AAA results in DAD.

I can confirm the issue with the following content in a file:

AAA
BBB
AAA
AAA

If I first select the 3 first lines, press Ctrl+F, and try to replace AAA by CCC, whether I use the Replace button repeatedly or the Replace All button, all 3 occurrences of AAA in the file are replaced while only two of them were initially in the selection.

In short, selecting a region of text prior to Ctrl+F has no effect, whatever the options chosen in the Search dialog.

When the Search+Replace widget of the editor is used to delete certain strings inside a selection, deletion occurs in the whole document instead.

Steps to reproduce:

1. In the editor, mark a piece of code
2. press Ctrl-F
3. In "search for" enter any string that is present in the selection
4. Leave "Replace by" empty
5. Make sure to check "search in selection"
6. Press "replace all"

Result: All instances of the search pattern throughout the whole document are deleted
Expected result: Deletion should occur only in the selected part.

If the search pattern is not found in the selected region, nothing happens, as it should be. If "replace by" is not empty, everything works fine.

A possible workaround is to extend the search string with another character, which should be kept. E.g. if there are many instances of "abc" and one wants to delete "ab", one should not replace "ab" with "", but "abc" with "c".

Since I'm at it currently, two little changes to the search widget would be nice:
If the widget is open and I select a new part of the code, the tick "search in selection" gets unchecked automatically, therefore I need to re-check it again. It would be nice if it stayed checked.
Also, the "replace all" action is done in many single replacements, therefore undoing (Ctrl-Z) such an action can get quite tedious. It would be nice if all replacements could be undone in a single step.