Cleanup folding method. Avoids header flags on lines which shouldn't …

…really have them. Seems to fix the mentioned issue.

Components/ScintEdit.pas

@@ -451,8 +451,8 @@   TScintCustomStyler = class(TComponent)
     function ConsumeString(const Chars: TScintRawCharSet): TScintRawString;
     function CurCharIn(const Chars: TScintRawCharSet): Boolean;
     function CurCharIs(const C: AnsiChar): Boolean;
-    procedure GetFoldLevel(const LineState: TScintLineState; var Level: Integer;
-      var Header: Boolean); virtual; abstract;
+    procedure GetFoldLevel(const LineState, NextLineState: TScintLineState;
+      var Level: Integer; var Header: Boolean); virtual; abstract;
     procedure GetStyleAttributes(const Style: Integer;
       var Attributes: TScintStyleAttributes); virtual; abstract;
     function LineTextSpans(const S: TScintRawString): Boolean; virtual;
@@ -1843,26 +1843,11 @@ procedure TScintEdit.StyleNeeded(const EndPos: Integer);
       FStyler.FStyleStr := '';
       FStyler.FText := '';
     end;
-
-    var FoldLevel: Integer;
-    var FoldHeader: Boolean;
-    FStyler.GetFoldLevel(FStyler.FLineState, FoldLevel, FoldHeader);
-    Inc(FoldLevel, SC_FOLDLEVELBASE);
-    if FoldHeader then
-      FoldLevel := FoldLevel or SC_FOLDLEVELHEADERFLAG;
-    { Setting SC_FOLDLEVELWHITEFLAG on empty lines causes a problem: when
-      Scintilla auto expands a contracted section (for example after removing ']'
-      from a section header) all the empty lines stay invisible, even any which
-      are in the middle of the section. }
-
+
     for var I := FirstLine to LastLine do begin
       var OldState := FLines.GetState(I);
       if FStyler.FLineState <> OldState then
         Call(SCI_SETLINESTATE, I, FStyler.FLineState);
-      { To display/debug fold levels use: FoldFlags := [sffLevelNumbers]; }
-      var OldLevel := Call(SCI_GETFOLDLEVEL, I, 0);
-      if FoldLevel <> OldLevel then
-        Call(SCI_SETFOLDLEVEL, I, FoldLevel);
     end;
 
     Result := LastLine;
@@ -1878,6 +1863,29 @@ procedure TScintEdit.StyleNeeded(const EndPos: Integer);
     Call(SCI_SETSTYLINGEX, Length(StyleStr), LPARAM(PAnsiChar(StyleStr)));
   end;
 
+  procedure FoldLine(const Line, EndLine: Integer);
+  begin
+    var LineState := FLines.GetState(Line);
+    var NextLineState: TScintLineState := 0;
+    if Line < EndLine then
+      NextLineState := FLines.GetState(Line+1);
+
+    var FoldLevel: Integer;
+    var FoldHeader: Boolean;
+    FStyler.GetFoldLevel(LineState, NextLineState, FoldLevel, FoldHeader);
+    Inc(FoldLevel, SC_FOLDLEVELBASE);
+    if FoldHeader then
+      FoldLevel := FoldLevel or SC_FOLDLEVELHEADERFLAG;
+    { Setting SC_FOLDLEVELWHITEFLAG on empty lines causes a problem: when
+      Scintilla auto expands a contracted section (for example after removing ']'
+      from a section header) all the empty lines stay invisible, even any which
+      are in the middle of the section. }
+
+    var OldLevel := Call(SCI_GETFOLDLEVEL, Line, 0);
+    if FoldLevel <> OldLevel then
+      Call(SCI_SETFOLDLEVEL, Line, FoldLevel);
+  end;
+
 var
   StartPos, StartLine, EndLine, Line: Integer;
 begin
@@ -1915,6 +1923,14 @@ procedure TScintEdit.StyleNeeded(const EndPos: Integer);
       DefaultStyleLine(Line);
     Inc(Line);
   end;
+
+  if Assigned(FStyler) then begin
+    Line := StartLine;
+    while Line <= EndLine do begin
+      FoldLine(Line, EndLine);
+      Inc(Line);
+    end;
+  end;
 end;
 
 procedure TScintEdit.SysColorChange(const Message: TMessage);

Components/ScintStylerInnoSetup.pas

@@ -105,8 +105,8 @@   TInnoSetupStyler = class(TScintCustomStyler)
     procedure SetISPPInstalled(const Value: Boolean);
   protected
     procedure CommitStyle(const Style: TInnoSetupStylerStyle);
-    procedure GetFoldLevel(const LineState: TScintLineState; var Level: Integer;
-      var Header: Boolean); override;
+    procedure GetFoldLevel(const LineState, NextLineState: TScintLineState;
+      var Level: Integer; var Header: Boolean); override;
     procedure GetStyleAttributes(const Style: Integer;
       var Attributes: TScintStyleAttributes); override;
     function LineTextSpans(const S: TScintRawString): Boolean; override;
@@ -937,31 +937,22 @@ function TInnoSetupStyler.GetFlagsWordList(Section: TInnoSetupStylerSection): An
   Result := FFlagsWordList[Section];
 end;
 
-procedure TInnoSetupStyler.GetFoldLevel(const LineState: TScintLineState;
+procedure TInnoSetupStyler.GetFoldLevel(const LineState, NextLineState: TScintLineState;
   var Level: Integer; var Header: Boolean);
 begin
-  { Set folding per section. To keep our code as simple as possible we simply
-    give all lines outside of a section (=lines at the start of the document and
-    section tags and section end tags and lines after section end tags) a header
-    flag. This avoids having to look at the previous line. Doesn't mean
-    Scintilla will display folding markers on all these header lines: it only
-    does that when there is something to fold, so when the header line is
-    followed a by non-header line which is only the case for a section tag line
-    followed by a section line.
-
-    Did notice an issue (Scintilla automatic folding bug?): Add a section with
-    some lines. Contract it. Break the section header for example by removing ']'.
-    Scintialla now auto expands the section and removes the fold mark.
-    Retype the ']'. Scintilla now displays the old fold mark to expand the
-    section but it's already expanded.  }
+  { Set folding per section. Lines outside of a section (=lines at the start of
+    the document and section tags and section end tags and lines after section
+    end tags) get level 0 with header flags for section tags. Other lines
+    (=lines inside a section) get level 1. }
 
   var Section := TInnoSetupStyler.GetSectionFromLineState(LineState);
-  if Section <> scNone then begin
+  if Section = scNone then begin
+    Level := 0;
+    var NextSection := TInnoSetupStyler.GetSectionFromLineState(NextLineState);
+    Header := NextSection <> scNone;
+  end else begin
     Level := 1;
     Header := False;
-  end else begin
-    Level := 0;
-    Header := True;
   end;
 end;