Preparatory changes for fix in next commit. Does not change Scintilla behaviour.

Add tests for contiguous deletions in forward and backward directions.
Use symbolic edition values.
Rename InsertionSpan to ChangeSpan and insertions to changes as holds both
insertions and deletions.
Add ChangeStack::Check.
Add comments.

1 files changed, 29 insertions, 13 deletions

diff --git a/src/ChangeHistory.cxx b/src/ChangeHistory.cxx
index 7295f89af..704f3f1c9 100644
--- a/src/ChangeHistory.cxx
+++ b/src/ChangeHistory.cxx
@@ -30,7 +30,7 @@ namespace Scintilla::Internal {
 
 void ChangeStack::Clear() noexcept {
 	steps.clear();
-	insertions.clear();
+	changes.clear();
 }
 
 void ChangeStack::AddStep() {
@@ -39,12 +39,12 @@ void ChangeStack::AddStep() {
 
 void ChangeStack::PushDeletion(Sci::Position positionDeletion, int edition) {
 	steps.back()++;
-	insertions.push_back({ positionDeletion, 0, edition, InsertionSpan::Direction::deletion });
+	changes.push_back({ positionDeletion, 0, edition, ChangeSpan::Direction::deletion });
 }
 
 void ChangeStack::PushInsertion(Sci::Position positionInsertion, Sci::Position length, int edition) {
 	steps.back()++;
-	insertions.push_back({ positionInsertion, length, edition, InsertionSpan::Direction::insertion });
+	changes.push_back({ positionInsertion, length, edition, ChangeSpan::Direction::insertion });
 }
 
 size_t ChangeStack::PopStep() noexcept {
@@ -53,21 +53,33 @@ size_t ChangeStack::PopStep() noexcept {
 	return spans;
 }
 
-InsertionSpan ChangeStack::PopSpan() noexcept {
-	const InsertionSpan span = insertions.back();
-	insertions.pop_back();
+ChangeSpan ChangeStack::PopSpan() noexcept {
+	const ChangeSpan span = changes.back();
+	changes.pop_back();
 	return span;
 }
 
 void ChangeStack::SetSavePoint() noexcept {
 	// Switch changeUnsaved to changeSaved
-	for (InsertionSpan &x : insertions) {
+	for (ChangeSpan &x : changes) {
 		if (x.edition == changeModified) {
 			x.edition = changeSaved;
 		}
 	}
 }
 
+void ChangeStack::Check() const noexcept {
+#ifdef _DEBUG
+	// Ensure count in steps same as insertions;
+	size_t sizeSteps = 0;
+	for (const size_t c : steps) {
+		sizeSteps += c;
+	}
+	const size_t sizeInsertions = changes.size();
+	assert(sizeSteps == sizeInsertions);
+#endif
+}
+
 void ChangeLog::Clear(Sci::Position length) {
 	changeStack.Clear();
 	insertEdition.DeleteAll();
@@ -167,13 +179,16 @@ void ChangeLog::PopDeletion(Sci::Position position, Sci::Position deleteLength)
 	editions->pop_back();
 	const size_t inserts = changeStack.PopStep();
 	for (size_t i = 0; i < inserts; i++) {
-		const InsertionSpan span = changeStack.PopSpan();
-		if (span.direction == InsertionSpan::Direction::insertion) {
+		const ChangeSpan span = changeStack.PopSpan();
+		if (span.direction == ChangeSpan::Direction::insertion) {
 			insertEdition.FillRange(span.start, span.edition, span.length);
 		} else {
 			assert(editions);
 			assert(editions->back() == span.edition);
 			editions->pop_back();
+			// Iterating backwards (pop) through changeStack, reverse order of insertion
+			// and original deletion list.
+			// Therefore need to insert at front to recreate original order.
 			InsertFrontDeletionAt(span.start, span.edition);
 		}
 	}
@@ -242,6 +257,7 @@ size_t ChangeLog::DeletionCount(Sci::Position start, Sci::Position length) const
 
 void ChangeLog::Check() const noexcept {
 	assert(insertEdition.Length() == deleteEdition.Length());
+	changeStack.Check();
 }
 
 ChangeHistory::ChangeHistory(Sci::Position length) {
@@ -270,7 +286,7 @@ void ChangeHistory::DeleteRange(Sci::Position position, Sci::Position deleteLeng
 	if (changeLogReversions) {
 		changeLogReversions->DeleteRangeSavingHistory(position, deleteLength);
 		if (reverting) {
-			changeLogReversions->PushDeletionAt(position, 1);
+			changeLogReversions->PushDeletionAt(position, changeRevertedOriginal);
 		}
 	}
 	Check();
@@ -349,9 +365,9 @@ int ChangeHistory::EditionAt(Sci::Position pos) const noexcept {
 	if (changeLogReversions) {
 		const int editionReversion = changeLogReversions->insertEdition.ValueAt(pos);
 		if (editionReversion) {
-			if (edition < 0)
-				return 1;
-			return edition ? 4 : 1;
+			if (edition < 0)	// Historical revision
+				return changeRevertedOriginal;
+			return edition ? changeRevertedToChange : changeRevertedOriginal;
 		}
 	}
 	return edition;