Fix Python folding collapse isuue

Fix Python folding collapse isuue by using a fold level stack.

Fix #1898, close #5131

PowerEditor/src/ScitillaComponent/ScintillaEditView.cpp

@@ -1949,8 +1949,80 @@ void ScintillaEditView::bufferUpdated(Buffer * buffer, int mask)
 	}
 }
 
+bool ScintillaEditView::isFoldIndentationBased() const
+{
+	const auto lexer = execute(SCI_GETLEXER);
+	// search IndentAmount in scintilla\lexers folder
+	return lexer == SCLEX_PYTHON
+		|| lexer == SCLEX_COFFEESCRIPT
+		|| lexer == SCLEX_HASKELL
+		|| lexer == SCLEX_NIMROD
+		|| lexer == SCLEX_VB
+		|| lexer == SCLEX_YAML
+	;
+}
+
+namespace {
+
+struct FoldLevelStack
+{
+	int levelCount = 0; // 1-based level number
+	int levelStack[MAX_FOLD_COLLAPSE_LEVEL]{};
+
+	void push(int level)
+	{
+		while (levelCount != 0 && level <= levelStack[levelCount - 1])
+		{
+			--levelCount;
+		}
+		levelStack[levelCount++] = level;
+	}
+};
+
+}
+
+void ScintillaEditView::collapseFoldIndentationBased(int level2Collapse, bool mode)
+{
+	execute(SCI_COLOURISE, 0, -1);
+
+	FoldLevelStack levelStack;
+	++level2Collapse; // 1-based level number
+
+	const int maxLine = static_cast<int32_t>(execute(SCI_GETLINECOUNT));
+	int line = 0;
+
+	while (line < maxLine)
+	{
+		int level = static_cast<int32_t>(execute(SCI_GETFOLDLEVEL, line));
+		if (level & SC_FOLDLEVELHEADERFLAG)
+		{
+			level &= SC_FOLDLEVELNUMBERMASK;
+			// don't need the actually level number, only the relationship.
+			levelStack.push(level);
+			if (level2Collapse == levelStack.levelCount)
+			{
+				if (isFolded(line) != mode)
+				{
+					fold(line, mode);
+				}
+				// skip all children lines, required to avoid buffer overrun.
+				line = static_cast<int32_t>(execute(SCI_GETLASTCHILD, line, -1));
+			}
+		}
+		++line;
+	}
+
+	runMarkers(true, 0, true, false);
+}
+
 void ScintillaEditView::collapse(int level2Collapse, bool mode)
 {
+	if (isFoldIndentationBased())
+	{
+		collapseFoldIndentationBased(level2Collapse, mode);
+		return;
+	}
+
 	execute(SCI_COLOURISE, 0, -1);
 
 	int maxLine = static_cast<int32_t>(execute(SCI_GETLINECOUNT));

PowerEditor/src/ScitillaComponent/ScintillaEditView.h

@@ -98,6 +98,7 @@ const int CP_GREEK = 1253;
 
 const bool fold_uncollapse = true;
 const bool fold_collapse = false;
+#define MAX_FOLD_COLLAPSE_LEVEL	8
 
 enum TextCase : UCHAR
 {
@@ -559,6 +560,8 @@ public:
 			::MessageBox(_hSelf, TEXT("This function needs a newer OS version."), TEXT("Change Case Error"), MB_OK | MB_ICONHAND);
 	};
 
+	bool isFoldIndentationBased() const;
+	void collapseFoldIndentationBased(int level2Collapse, bool mode);
 	void collapse(int level2Collapse, bool mode);
 	void foldAll(bool mode);
 	void fold(size_t line, bool mode);