From e5f0fad791b6de839d1b62c8b0a1ac624b8a2025 Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Fri, 17 May 2019 09:02:10 +1000
Subject: Backport: Optimize InsertLines and DeleteLines for ContractionState
 if no folds contracted.

Backport of changeset 7500:c4db961b46ab.
---
 doc/ScintillaHistory.html |  4 ++++
 src/ContractionState.cxx  | 16 ++++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index c1e9f5fc9..d3eae6697 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -554,6 +554,10 @@
 	<a href="https://sourceforge.net/p/scintilla/feature-requests/1280/">Feature #1280</a>.
 	</li>
 	<li>
+	Improved performance of line folding code on large files when no folds are contracted.
+	This improves the time taken to open or close large files.
+	</li>
+	<li>
 	Fix bug where changing identifier sets in lexers preserved previous identifiers.
 	</li>
 	<li>
diff --git a/src/ContractionState.cxx b/src/ContractionState.cxx
index 47f345ada..ebbf9aefe 100644
--- a/src/ContractionState.cxx
+++ b/src/ContractionState.cxx
@@ -209,16 +209,24 @@ Sci::Line ContractionState<LINE>::DocFromDisplay(Sci::Line lineDisplay) const {
 
 template <typename LINE>
 void ContractionState<LINE>::InsertLines(Sci::Line lineDoc, Sci::Line lineCount) {
-	for (Sci::Line l = 0; l < lineCount; l++) {
-		InsertLine(lineDoc + l);
+	if (OneToOne()) {
+		linesInDocument += static_cast<LINE>(lineCount);
+	} else {
+		for (Sci::Line l = 0; l < lineCount; l++) {
+			InsertLine(lineDoc + l);
+		}
 	}
 	Check();
 }
 
 template <typename LINE>
 void ContractionState<LINE>::DeleteLines(Sci::Line lineDoc, Sci::Line lineCount) {
-	for (Sci::Line l = 0; l < lineCount; l++) {
-		DeleteLine(lineDoc);
+	if (OneToOne()) {
+		linesInDocument -= static_cast<LINE>(lineCount);
+	} else {
+		for (Sci::Line l = 0; l < lineCount; l++) {
+			DeleteLine(lineDoc);
+		}
 	}
 	Check();
 }
-- 
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