#1799 Expanding folds when merging two collapsed blocks

[Markus Nißl]

In our Scintilla based editor, we support folding of consecutive comment lines, i.e. lines that only consists of line comments, e.g.:

// line 1
// line 2

This means that two separate blocks can be merged by either deleting the separating line or by making the separating line a line comment as well:

// line 1 of block 1
// line 2 of block 1

// line 1 of block 2
// line 2 of block 2

If the two blocks are collapsed, Scintilla by default doesn't handle the merging correctly regarding the fold state: the two blocks need to be expanded. The attached patch implements this behaviour in Editor::FoldChanged().

[Neil Hodgson]

Starting with this C document:

a {
b
}
c {
d
}

where structure 'a' is collapsed, the patch will expand 'a' when the '{' after 'c' is removed.

[Markus Nißl]

The attached patch fixes this. The previous block may only be expanded if the fold levels are the same.

[Neil Hodgson]

Its the second hunk in the patch that triggers for the "adding characters in the line" case such as when using Perl in SciTE with fold.compact=0 and this document when a '#' is added to line 3:

##
##

##
##

Is there an example that triggers the FoldLine in hunk 1?

Are there any circumstyances in which FoldLines in the patch should collapse? If not then SC_FOLDACTION_EXPAND should be used instead of SC_FOLDACTION_TOGGLE.

Scintilla must still build with with C++03 so auto for declarations is not possible.

[Markus Nißl]

My bad: I mixed up the two comments.

The new patch fixes the comments and states the cases more precisely. I added one more comment that handles the case "Combining two blocks where the second one is collapsed". I also replaced the auto keyword with the data types.

Yes, the folds should always expand, never collapse.

BTW: what's the difference between Editor::FoldLine(line, SC_FOLDACTION_EXPAND) and Editor::FoldExpand(line, SC_FOLDACTION_EXPAND, level)?

[Neil Hodgson]

I haven't found a case where this breaks but I suspect this line needs to mask the levels with SC_FOLDLEVELNUMBERMASK:

    if (prevLineLevel == levelNow && !cs.GetVisible(prevLine))

may change to

    if (((prevLineLevel & SC_FOLDLEVELNUMBERMASK) == 
              (levelNow & SC_FOLDLEVELNUMBERMASK)) &&
           !cs.GetVisible(prevLine))

[Markus Nißl]

Yes, your suggestion will be safer as from a logical point of view, we only want to compare the depth of folding, not taking into account any additional flags.

[Neil Hodgson]

Fix committed as [def6d8]. SciTE version in [21ad2b].

[Neil Hodgson]

There are problems with this change mentioned in [#1896]. Making this change more selective may avoid it failing as described.