diff --git a/scintilla/README b/scintilla/README
index e71982012..9884bc414 100644
--- a/scintilla/README
+++ b/scintilla/README
@@ -2,4 +2,4 @@ This is only a repository to track Scintilla (https://sourceforge.net/p/scintill
 resp. (http://hg.code.sf.net/p/scintilla/code)
 resp. GitHub Mirror: (https://github.com/missdeer/scintilla)
 changes for Notepad3 (https://github.com/rizonesoft/Notepad3) development.
- 
+
diff --git a/scintilla/doc/ScintillaDoc.html b/scintilla/doc/ScintillaDoc.html
index 30411853e..0b8594f79 100644
--- a/scintilla/doc/ScintillaDoc.html
+++ b/scintilla/doc/ScintillaDoc.html
@@ -7982,7 +7982,7 @@ sptr_t CallScintilla(unsigned int iMessage, uptr_t wParam, sptr_t lParam){
 
     <p><b id="SCI_SETLAYOUTTHREADS">SCI_SETLAYOUTTHREADS(int threads)</b><br />
      <b id="SCI_GETLAYOUTTHREADS">SCI_GETLAYOUTTHREADS &rarr; int</b><br />
-     The time taken to measure text runs on wide lines can be improved by performing the task
+     The time taken to measure text runs on wide lines or when wrapping can be improved by performing the task
      concurrently on multiple threads when
      <a class="seealso" href="#SCI_SUPPORTSFEATURE">SCI_SUPPORTSFEATURE(SC_SUPPORTS_THREAD_SAFE_MEASURE_WIDTHS)</a>
      is available.
diff --git a/scintilla/doc/ScintillaDownload.html b/scintilla/doc/ScintillaDownload.html
index 7316834a3..f66689698 100644
--- a/scintilla/doc/ScintillaDownload.html
+++ b/scintilla/doc/ScintillaDownload.html
@@ -26,9 +26,9 @@
     <table bgcolor="#CCCCCC" width="100%" cellspacing="0" cellpadding="8" border="0">
       <tr>
         <td>
-          <font size="4"> <a href="https://www.scintilla.org/scintilla533.zip">
+          <font size="4"> <a href="https://www.scintilla.org/scintilla534.zip">
 	Windows</a>&nbsp;&nbsp;
-	<a href="https://www.scintilla.org/scintilla533.tgz">
+	<a href="https://www.scintilla.org/scintilla534.tgz">
           GTK/Linux</a>&nbsp;&nbsp;
 	</font>
         </td>
@@ -42,7 +42,7 @@
       containing very few restrictions.
     </p>
     <h3>
-       Release 5.3.3
+       Release 5.3.4
     </h3>
     <h4>
        Source Code
@@ -50,8 +50,8 @@
        The source code package contains all of the source code for Scintilla but no binary
 	executable code and is available in
        <ul>
-       <li><a href="https://www.scintilla.org/scintilla533.zip">zip format</a> (1.4M) commonly used on Windows</li>
-       <li><a href="https://www.scintilla.org/scintilla533.tgz">tgz format</a> (1.3M) commonly used on Linux and compatible operating systems</li>
+       <li><a href="https://www.scintilla.org/scintilla534.zip">zip format</a> (1.4M) commonly used on Windows</li>
+       <li><a href="https://www.scintilla.org/scintilla534.tgz">tgz format</a> (1.3M) commonly used on Linux and compatible operating systems</li>
        </ul>
        Instructions for building on both Windows and Linux are included in the readme file.
     <h4>
diff --git a/scintilla/doc/ScintillaHistory.html b/scintilla/doc/ScintillaHistory.html
index 7e544789c..1d9222cea 100644
--- a/scintilla/doc/ScintillaHistory.html
+++ b/scintilla/doc/ScintillaHistory.html
@@ -584,7 +584,10 @@
     </h3>
     <ul>
 	<li>
-	Released 8 February 2023.
+	Released 8 March 2023.
+	</li>
+	<li>
+	Add multithreaded wrap to significantly improve performance of wrapping large files.
 	</li>
 	<li>
 	More typesafe bindings of *Full APIs in ScintillaCall.
diff --git a/scintilla/doc/index.html b/scintilla/doc/index.html
index 4cb270530..646c4cb63 100644
--- a/scintilla/doc/index.html
+++ b/scintilla/doc/index.html
@@ -9,7 +9,7 @@
     <meta name="keywords" content="Scintilla, SciTE, Editing Component, Text Editor" />
     <meta name="Description"
     content="www.scintilla.org is the home of the Scintilla editing component and SciTE text editor application." />
-    <meta name="Date.Modified" content="20230208" />
+    <meta name="Date.Modified" content="20230308" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <style type="text/css">
         #versionlist {
@@ -56,8 +56,8 @@
           GTK, and macOS</font>
         </td>
         <td width="40%" align="right">
-          <font color="#FFCC99" size="3"> Release version 5.3.3<br />
-           Site last modified February 8 2023</font>
+          <font color="#FFCC99" size="3"> Release version 5.3.4<br />
+           Site last modified March 8 2023</font>
         </td>
         <td width="20%">
           &nbsp;
@@ -72,12 +72,12 @@
       </tr>
     </table>
     <ul id="versionlist">
+      <li>Version 5.3.4 adds multithreaded wrapping.</li>
       <li>Version 5.3.3 fixes minor bugs in APIs and platform layers.</li>
       <li>Version 5.3.2 adds SCI_REPLACETARGETMINIMAL to modify text without marking unchanged start and end text in change history.</li>
       <li>Version 5.3.1 can represent invisible text with a character to simplify editing and provide summarized views.</li>
       <li>Version 5.3.0 adds change history.</li>
       <li>Version 5.2.4 fixes failures on GTK with multi-threaded layout.</li>
-      <li>Version 5.2.3 adds 64-bit safe APIs and fixes scrollbar on GTK with Xorg.</li>
     </ul>
     <ul id="menu">
       <li id="remote1"><a href="https://www.scintilla.org/SciTEImage.html">Screenshot</a></li>
diff --git a/scintilla/scripts/CheckMentioned.py b/scintilla/scripts/CheckMentioned.py
index 0cf8aefa4..72b6b49f4 100644
--- a/scintilla/scripts/CheckMentioned.py
+++ b/scintilla/scripts/CheckMentioned.py
@@ -161,7 +161,7 @@ def checkDocumentation():
 		#~ if api not in headers:
 			#~ print("No header for ", api)
 
-	# Examine  definitions
+	# Examine definitions
 	#<b id="SCI_SETLAYOUTCACHE">SCI_SETLAYOUTCACHE(int cacheMode)</b>
 	defPattern = re.compile(r'<b id="([A-Z_0-9]+)">([A-Z][A-Za-z0-9_() *#\"=<>/&;,\n-]+?)</b>')
 	for api, sig in re.findall(defPattern, docs):
@@ -201,7 +201,7 @@ def checkDocumentation():
 	with open(outName, "wt") as docFile:
 		docFile.write(docs)
 
-	# Examine  constant definitions
+	# Examine constant definitions
 	#<code>SC_CARETSTICKY_WHITESPACE</code> (2)
 	constPattern = re.compile(r'<code>(\w+)</code> *\((\w+)\)')
 	for name, val in re.findall(constPattern, docs):
diff --git a/scintilla/scripts/LexGen.py b/scintilla/scripts/LexGen.py
index fba9f6631..a999621d6 100644
--- a/scintilla/scripts/LexGen.py
+++ b/scintilla/scripts/LexGen.py
@@ -34,7 +34,7 @@ def UpdateVersionNumbers(sci, root):
     UpdateLineInFile(root / "doc/ScintillaDownload.html", "       Release",
         "       Release " + sci.versionDotted)
     ReplaceREInFile(root / "doc/ScintillaDownload.html",
-        r"/www.scintilla.org/([a-zA-Z]+)\d\d\d",
+        r"/www.scintilla.org/([a-zA-Z]+)\d{3,5}",
         r"/www.scintilla.org/\g<1>" +  sci.version,
         0)
     UpdateLineInFile(root / "doc/index.html",
diff --git a/scintilla/scripts/ScintillaData.py b/scintilla/scripts/ScintillaData.py
index 355b5d471..857da7dd5 100644
--- a/scintilla/scripts/ScintillaData.py
+++ b/scintilla/scripts/ScintillaData.py
@@ -49,8 +49,8 @@ class ScintillaData:
     def __init__(self, scintillaRoot):
         # Discover version information
         self.version = (scintillaRoot / "version.txt").read_text().strip()
-        self.versionDotted = self.version[0] + '.' + self.version[1] + '.' + \
-            self.version[2]
+        self.versionDotted = self.version[0:-2] + '.' + self.version[-2] + '.' + \
+            self.version[-1]
         self.versionCommad = self.versionDotted.replace(".", ", ") + ', 0'
 
         with (scintillaRoot / "doc" / "index.html").open() as f:
diff --git a/scintilla/src/CaseConvert.cxx b/scintilla/src/CaseConvert.cxx
index 601432f14..f5513ab90 100644
--- a/scintilla/src/CaseConvert.cxx
+++ b/scintilla/src/CaseConvert.cxx
@@ -605,7 +605,6 @@ class CaseConverter : public ICaseConverter {
 			return character < other.character;
 		}
 	};
-	CaseConversion conversion;
 	typedef std::vector<CharacterConversion> CharacterToConversion;
 	CharacterToConversion characterToConversion;
 	// The parallel arrays
@@ -613,8 +612,7 @@ class CaseConverter : public ICaseConverter {
 	std::vector<ConversionString> conversions;
 
 public:
-	explicit CaseConverter(CaseConversion conversion_) : conversion(conversion_) {
-	};
+	CaseConverter() noexcept = default;
 	// Deleted so CaseConverter objects can not be copied.
 	CaseConverter(const CaseConverter &) = delete;
 	CaseConverter(CaseConverter &&) = delete;
@@ -690,15 +688,13 @@ public:
 		// Empty the original calculated data completely
 		CharacterToConversion().swap(characterToConversion);
 	}
-	void AddSymmetric(int lower, int upper);
-	void SetupConversions();
+	void AddSymmetric(CaseConversion conversion, int lower, int upper);
+	void SetupConversions(CaseConversion conversion);
 };
 
-CaseConverter caseConvFold(CaseConversion::fold);
-CaseConverter caseConvUp(CaseConversion::upper);
-CaseConverter caseConvLow(CaseConversion::lower);
+CaseConverter caseConvList[3];
 
-void CaseConverter::AddSymmetric(int lower, int upper) {
+void CaseConverter::AddSymmetric(CaseConversion conversion, int lower, int upper) {
 	const int character = (conversion == CaseConversion::upper) ? lower : upper;
 	const int source = (conversion == CaseConversion::upper) ? upper : lower;
 	char converted[maxConversionLength+1]{};
@@ -720,7 +716,7 @@ std::string_view NextField(std::string_view &view) {
 	return field;
 }
 
-void CaseConverter::SetupConversions() {
+void CaseConverter::SetupConversions(CaseConversion conversion) {
 	// First initialize for the symmetric ranges
 	for (size_t i=0; i<std::size(symmetricCaseConversionRanges);) {
 		const int lower = symmetricCaseConversionRanges[i++];
@@ -728,14 +724,14 @@ void CaseConverter::SetupConversions() {
 		const int length = symmetricCaseConversionRanges[i++];
 		const int pitch = symmetricCaseConversionRanges[i++];
 		for (int j=0; j<length*pitch; j+=pitch) {
-			AddSymmetric(lower+j, upper+j);
+			AddSymmetric(conversion, lower+j, upper+j);
 		}
 	}
 	// Add the symmetric singletons
 	for (size_t i=0; i<std::size(symmetricCaseConversions);) {
 		const int lower = symmetricCaseConversions[i++];
 		const int upper = symmetricCaseConversions[i++];
-		AddSymmetric(lower, upper);
+		AddSymmetric(conversion, lower, upper);
 	}
 	// Add the complex cases
 	std::string_view sComplex = complexCaseConversions;
@@ -768,21 +764,11 @@ void CaseConverter::SetupConversions() {
 }
 
 CaseConverter *ConverterForConversion(CaseConversion conversion) {
-	CaseConverter *pCaseConv = &caseConvFold;
-	switch (conversion) {
-	case CaseConversion::fold:
-		pCaseConv = &caseConvFold;
-		break;
-	case CaseConversion::upper:
-		pCaseConv = &caseConvUp;
-		break;
-	case CaseConversion::lower:
-	default:
-		pCaseConv = &caseConvLow;
-		break;
-	}
+	const unsigned index = static_cast<unsigned>(conversion);
+	assert(index < std::size(caseConvList));
+	CaseConverter *pCaseConv = &caseConvList[index];
 	if (!pCaseConv->Initialised()) {
-		pCaseConv->SetupConversions();
+		pCaseConv->SetupConversions(conversion);
 	}
 	return pCaseConv;
 }
diff --git a/scintilla/src/Document.cxx b/scintilla/src/Document.cxx
index 54547a149..7a3352a72 100644
--- a/scintilla/src/Document.cxx
+++ b/scintilla/src/Document.cxx
@@ -448,6 +448,10 @@ Sci_Position SCI_METHOD Document::LineStart(Sci_Position line) const noexcept {
 	return cb.LineStart(line);
 }
 
+Range Document::LineRange(Sci::Line line) const noexcept {
+	return {cb.LineStart(line), cb.LineStart(line + 1)};
+}
+
 bool Document::IsLineStartPosition(Sci::Position position) const {
 	return LineStart(LineFromPosition(position)) == position;
 }
diff --git a/scintilla/src/Document.h b/scintilla/src/Document.h
index d2801f7c5..cdac2276b 100644
--- a/scintilla/src/Document.h
+++ b/scintilla/src/Document.h
@@ -54,6 +54,10 @@ public:
 		return start == end;
 	}
 
+	[[nodiscard]] Sci::Position Length() const noexcept {
+		return (start <= end) ? (end - start) : (start - end);
+	}
+
 	Sci::Position First() const noexcept {
 		return (start <= end) ? start : end;
 	}
@@ -454,6 +458,7 @@ public:
 	int MarkerNumberFromLine(Sci::Line line, int which) const noexcept;
 	int MarkerHandleFromLine(Sci::Line line, int which) const noexcept;
 	Sci_Position SCI_METHOD LineStart(Sci_Position line) const noexcept override;
+	[[nodiscard]] Range LineRange(Sci::Line line) const noexcept;
 	bool IsLineStartPosition(Sci::Position position) const;
 	Sci_Position SCI_METHOD LineEnd(Sci_Position line) const noexcept override;
 	Sci::Position LineEndPosition(Sci::Position position) const;
diff --git a/scintilla/src/EditView.cxx b/scintilla/src/EditView.cxx
index 3bc7289b0..e39339125 100644
--- a/scintilla/src/EditView.cxx
+++ b/scintilla/src/EditView.cxx
@@ -397,7 +397,7 @@ void LayoutSegments(IPositionCache *pCache,
 * Copy the given @a line and its styles from the document into local arrays.
 * Also determine the x position at which each character starts.
 */
-void EditView::LayoutLine(const EditModel &model, Surface *surface, const ViewStyle &vstyle, LineLayout *ll, int width) {
+void EditView::LayoutLine(const EditModel &model, Surface *surface, const ViewStyle &vstyle, LineLayout *ll, int width, bool callerMultiThreaded) {
 	if (!ll)
 		return;
 
@@ -494,7 +494,7 @@ void EditView::LayoutLine(const EditModel &model, Surface *surface, const ViewSt
 
 			const size_t threadsForLength = std::max(1, numCharsInLine / bytesPerLayoutThread);
 			size_t threads = std::min<size_t>({ segments.size(), threadsForLength, maxLayoutThreads });
-			if (!surface->SupportsFeature(Supports::ThreadSafeMeasureWidths)) {
+			if (!surface->SupportsFeature(Supports::ThreadSafeMeasureWidths) || callerMultiThreaded) {
 				threads = 1;
 			}
 
@@ -502,6 +502,7 @@ void EditView::LayoutLine(const EditModel &model, Surface *surface, const ViewSt
 
 			const bool textUnicode = CpUtf8 == model.pdoc->dbcsCodePage;
 			const bool multiThreaded = threads > 1;
+			const bool multiThreadedContext = multiThreaded || callerMultiThreaded;
 			IPositionCache *pCache = posCache.get();
 
 			// If only 1 thread needed then use the main thread, else spin up multiple
@@ -511,8 +512,8 @@ void EditView::LayoutLine(const EditModel &model, Surface *surface, const ViewSt
 			for (size_t th = 0; th < threads; th++) {
 				// Find relative positions of everything except for tabs
 				std::future<void> fut = std::async(policy,
-					[pCache, surface, &vstyle, &ll, &segments, &nextIndex, textUnicode, multiThreaded]() {
-					LayoutSegments(pCache, surface, vstyle, ll, segments, nextIndex, textUnicode, multiThreaded);
+					[pCache, surface, &vstyle, &ll, &segments, &nextIndex, textUnicode, multiThreadedContext]() {
+					LayoutSegments(pCache, surface, vstyle, ll, segments, nextIndex, textUnicode, multiThreadedContext);
 				});
 				futures.push_back(std::move(fut));
 			}
diff --git a/scintilla/src/EditView.h b/scintilla/src/EditView.h
index 833fbca20..ce44db2cc 100644
--- a/scintilla/src/EditView.h
+++ b/scintilla/src/EditView.h
@@ -119,7 +119,7 @@ public:
 
 	std::shared_ptr<LineLayout> RetrieveLineLayout(Sci::Line lineNumber, const EditModel &model);
 	void LayoutLine(const EditModel &model, Surface *surface, const ViewStyle &vstyle,
-		LineLayout *ll, int width);
+		LineLayout *ll, int width, bool callerMultiThreaded=false);
 
 	static void UpdateBidiData(const EditModel &model, const ViewStyle &vstyle, LineLayout *ll);
 
diff --git a/scintilla/src/Editor.cxx b/scintilla/src/Editor.cxx
index 95d86f372..be83b3fb5 100644
--- a/scintilla/src/Editor.cxx
+++ b/scintilla/src/Editor.cxx
@@ -25,6 +25,9 @@
 #include <iterator>
 #include <memory>
 #include <chrono>
+#include <atomic>
+#include <thread>
+#include <future>
 
 #include "ScintillaTypes.h"
 #include "ScintillaMessages.h"
@@ -274,6 +277,11 @@ Sci::Line Editor::TopLineOfMain() const noexcept {
 		return topLine;
 }
 
+Point Editor::ClientSize() const {
+	const PRectangle rcClient = GetClientRectangle();
+	return Point(rcClient.Width(), rcClient.Height());
+}
+
 PRectangle Editor::GetClientRectangle() const {
 	return wMain.GetClientPosition();
 }
@@ -290,8 +298,8 @@ PRectangle Editor::GetTextRectangle() const {
 }
 
 Sci::Line Editor::LinesOnScreen() const {
-	const PRectangle rcClient = GetClientRectangle();
-	const int htClient = static_cast<int>(rcClient.bottom - rcClient.top);
+	const Point sizeClient = ClientSize();
+	const int htClient = static_cast<int>(sizeClient.y);
 	//Platform::DebugPrintf("lines on screen = %d\n", htClient / lineHeight + 1);
 	return htClient / vs.lineHeight;
 }
@@ -1468,6 +1476,130 @@ bool Editor::WrapOneLine(Surface *surface, Sci::Line lineToWrap) {
 	return pcs->SetHeight(lineToWrap, linesWrapped);
 }
 
+namespace {
+
+// Lines less than lengthToMultiThread are laid out in blocks in parallel.
+// Longer lines are multi-threaded inside LayoutLine.
+// This allows faster processing when lines differ greatly in length and thus time to lay out.
+constexpr Sci::Position lengthToMultiThread = 4000;
+
+}
+
+bool Editor::WrapBlock(Surface *surface, Sci::Line lineToWrap, Sci::Line lineToWrapEnd) {
+
+	const size_t linesBeingWrapped = static_cast<size_t>(lineToWrapEnd - lineToWrap);
+
+	std::vector<int> linesAfterWrap(linesBeingWrapped);
+
+	size_t threads = std::min<size_t>({ linesBeingWrapped, view.maxLayoutThreads });
+	if (!surface->SupportsFeature(Supports::ThreadSafeMeasureWidths)) {
+		threads = 1;
+	}
+
+	const bool multiThreaded = threads > 1;
+
+	ElapsedPeriod epWrapping;
+
+	// Wrap all the short lines in multiple threads
+
+	// If only 1 thread needed then use the main thread, else spin up multiple
+	const std::launch policy = multiThreaded ? std::launch::async : std::launch::deferred;
+
+	std::atomic<size_t> nextIndex = 0;
+
+	// Lines that are less likely to be re-examined should not be read from or written to the cache.
+	const SignificantLines significantLines {
+		pdoc->SciLineFromPosition(sel.MainCaret()),
+		pcs->DocFromDisplay(topLine),
+		LinesOnScreen() + 1,
+		view.llc.GetLevel(),
+	};
+
+	// Protect the line layout cache from being accessed from multiple threads simultaneously
+	std::mutex mutexRetrieve;
+
+	std::vector<std::future<void>> futures;
+	for (size_t th = 0; th < threads; th++) {
+		std::future<void> fut = std::async(policy,
+			[=, &surface, &nextIndex, &linesAfterWrap, &mutexRetrieve]() {
+			// llTemporary is reused for non-significant lines, avoiding allocation costs.
+			std::shared_ptr<LineLayout> llTemporary = std::make_shared<LineLayout>(-1, 200);
+			while (true) {
+				const size_t i = nextIndex.fetch_add(1, std::memory_order_acq_rel);
+				if (i >= linesBeingWrapped) {
+					break;
+				}
+				const Sci::Line lineNumber = lineToWrap + i;
+				const Range rangeLine = pdoc->LineRange(lineNumber);
+				const Sci::Position lengthLine = rangeLine.Length();
+				if (lengthLine < lengthToMultiThread) {
+					std::shared_ptr<LineLayout> ll;
+					if (significantLines.LineMayCache(lineNumber)) {
+						std::lock_guard<std::mutex> guard(mutexRetrieve);
+						ll = view.RetrieveLineLayout(lineNumber, *this);
+					} else {
+						ll = llTemporary;
+						ll->ReSet(lineNumber, lengthLine);
+					}
+					view.LayoutLine(*this, surface, vs, ll.get(), wrapWidth, multiThreaded);
+					linesAfterWrap[i] = ll->lines;
+				}
+			}
+		});
+		futures.push_back(std::move(fut));
+	}
+	for (const std::future<void> &f : futures) {
+		f.wait();
+	}
+	// End of multiple threads
+
+	// Multiply duration by number of threads to produce (near) equivalence to duration if single threaded
+	const double durationShortLines = epWrapping.Duration(true);
+	const double durationShortLinesThreads = durationShortLines * threads;
+
+	// Wrap all the long lines in the main thread.
+	// LayoutLine may then multi-thread over segments in each line.
+
+	std::shared_ptr<LineLayout> llLarge = std::make_shared<LineLayout>(-1, 200);
+	for (size_t indexLarge = 0; indexLarge < linesBeingWrapped; indexLarge++) {
+		const Sci::Line lineNumber = lineToWrap + indexLarge;
+		const Range rangeLine = pdoc->LineRange(lineNumber);
+		const Sci::Position lengthLine = rangeLine.Length();
+		if (lengthLine >= lengthToMultiThread) {
+			std::shared_ptr<LineLayout> ll;
+			if (significantLines.LineMayCache(lineNumber)) {
+				ll = view.RetrieveLineLayout(lineNumber, *this);
+			} else {
+				ll = llLarge;
+				ll->ReSet(lineNumber, lengthLine);
+			}
+			view.LayoutLine(*this, surface, vs, ll.get(), wrapWidth);
+			linesAfterWrap[indexLarge] = ll->lines;
+		}
+	}
+
+	const double durationLongLines = epWrapping.Duration();
+	const size_t bytesBeingWrapped = pdoc->LineStart(lineToWrap + linesBeingWrapped) - pdoc->LineStart(lineToWrap);
+
+	size_t wrapsDone = 0;
+
+	for (size_t i = 0; i < linesBeingWrapped; i++) {
+		const Sci::Line lineNumber = lineToWrap + i;
+		int linesWrapped = linesAfterWrap[i];
+		if (vs.annotationVisible != AnnotationVisible::Hidden) {
+			linesWrapped += pdoc->AnnotationLines(lineNumber);
+		}
+		if (pcs->SetHeight(lineNumber, linesWrapped)) {
+			wrapsDone++;
+		}
+		wrapPending.Wrapped(lineNumber);
+	}
+
+	durationWrapOneByte.AddSample(bytesBeingWrapped, durationShortLinesThreads + durationLongLines);
+
+	return wrapsDone > 0;
+}
+
 // Perform  wrapping for a subset of the lines needing wrapping.
 // wsAll: wrap all lines which need wrapping in this single call
 // wsVisible: wrap currently visible lines
@@ -1549,16 +1681,7 @@ bool Editor::WrapLines(WrapScope ws) {
 			if (surface) {
 //Platform::DebugPrintf("Wraplines: scope=%0d need=%0d..%0d perform=%0d..%0d\n", ws, wrapPending.start, wrapPending.end, lineToWrap, lineToWrapEnd);
 
-				const size_t bytesBeingWrapped = pdoc->LineStart(lineToWrapEnd) - pdoc->LineStart(lineToWrap);
-				ElapsedPeriod epWrapping;
-				while (lineToWrap < lineToWrapEnd) {
-					if (WrapOneLine(surface, lineToWrap)) {
-						wrapOccurred = true;
-					}
-					wrapPending.Wrapped(lineToWrap);
-					lineToWrap++;
-				}
-				durationWrapOneByte.AddSample(bytesBeingWrapped, epWrapping.Duration());
+				wrapOccurred = WrapBlock(surface, lineToWrap, lineToWrapEnd);
 
 				goodTopLine = pcs->DisplayFromDoc(lineDocTop) + std::min(
 					subLineTop, static_cast<Sci::Line>(pcs->GetHeight(lineDocTop)-1));
diff --git a/scintilla/src/Editor.h b/scintilla/src/Editor.h
index 692073b9e..6c077b747 100644
--- a/scintilla/src/Editor.h
+++ b/scintilla/src/Editor.h
@@ -312,6 +312,7 @@ protected:	// ScintillaBase subclass needs access to much of Editor
 	Point GetVisibleOriginInMain() const override;
 	PointDocument DocumentPointFromView(Point ptView) const;  // Convert a point from view space to document
 	Sci::Line TopLineOfMain() const noexcept final;   // Return the line at Main's y coordinate 0
+	virtual Point ClientSize() const;
 	virtual PRectangle GetClientRectangle() const;
 	virtual PRectangle GetClientDrawingRectangle();
 	PRectangle GetTextRectangle() const;
@@ -403,6 +404,7 @@ protected:	// ScintillaBase subclass needs access to much of Editor
 	bool Wrapping() const noexcept;
 	void NeedWrapping(Sci::Line docLineStart=0, Sci::Line docLineEnd=WrapPending::lineLarge);
 	bool WrapOneLine(Surface *surface, Sci::Line lineToWrap);
+	bool WrapBlock(Surface *surface, Sci::Line lineToWrap, Sci::Line lineToWrapEnd);
 	enum class WrapScope {wsAll, wsVisible, wsIdle};
 	bool WrapLines(WrapScope ws);
 	void LinesJoin();
diff --git a/scintilla/src/PositionCache.cxx b/scintilla/src/PositionCache.cxx
index 569583b35..4c142d48f 100644
--- a/scintilla/src/PositionCache.cxx
+++ b/scintilla/src/PositionCache.cxx
@@ -102,6 +102,13 @@ void LineLayout::Resize(int maxLineLength_) {
 	}
 }
 
+void LineLayout::ReSet(Sci::Line lineNumber_, Sci::Position maxLineLength_) {
+	lineNumber = lineNumber_;
+	Resize(static_cast<int>(maxLineLength_));
+	lines = 0;
+	Invalidate(ValidLevel::invalid);
+}
+
 void LineLayout::EnsureBidiData() {
 	if (!bidiData) {
 		bidiData = std::make_unique<BidiData>();
@@ -114,6 +121,7 @@ void LineLayout::Free() noexcept {
 	styles.reset();
 	positions.reset();
 	lineStarts.reset();
+	lenLineStarts = 0;
 	bidiData.reset();
 }
 
@@ -446,6 +454,21 @@ XYPOSITION ScreenLine::TabPositionAfter(XYPOSITION xPosition) const noexcept {
 	return (std::floor((xPosition + TabWidthMinimumPixels()) / TabWidth()) + 1) * TabWidth();
 }
 
+bool SignificantLines::LineMayCache(Sci::Line line) const noexcept {
+	switch (level) {
+	case LineCache::None:
+		return false;
+	case LineCache::Caret:
+		return line == lineCaret;
+	case LineCache::Page:
+		return (abs(line - lineCaret) < linesOnScreen) ||
+			((line >= lineTop) && (line <= (lineTop + linesOnScreen)));
+	case LineCache::Document:
+	default:
+		return true;
+	}
+}
+
 LineLayoutCache::LineLayoutCache() :
 	level(LineCache::None),
 	allInvalidated(false), styleClock(-1) {
diff --git a/scintilla/src/PositionCache.h b/scintilla/src/PositionCache.h
index 6263a07a8..64884ba0f 100644
--- a/scintilla/src/PositionCache.h
+++ b/scintilla/src/PositionCache.h
@@ -83,6 +83,7 @@ public:
 	void operator=(LineLayout &&) = delete;
 	virtual ~LineLayout();
 	void Resize(int maxLineLength_);
+	void ReSet(Sci::Line lineNumber_, Sci::Position maxLineLength_);
 	void EnsureBidiData();
 	void Free() noexcept;
 	void ClearPositions();
@@ -140,6 +141,14 @@ struct ScreenLine : public IScreenLine {
 	XYPOSITION TabPositionAfter(XYPOSITION xPosition) const noexcept override;
 };
 
+struct SignificantLines {
+	Sci::Line lineCaret;
+	Sci::Line lineTop;
+	Sci::Line linesOnScreen;
+	Scintilla::LineCache level;
+	bool LineMayCache(Sci::Line line) const noexcept;
+};
+
 /**
  */
 class LineLayoutCache {
diff --git a/scintilla/version.txt b/scintilla/version.txt
index 910fbe3bd..2d8c4cdf7 100644
--- a/scintilla/version.txt
+++ b/scintilla/version.txt
@@ -1 +1 @@
-533
+534
diff --git a/scintilla/win32/ScintRes.rc b/scintilla/win32/ScintRes.rc
index 0cb40de58..d2c2d8508 100644
--- a/scintilla/win32/ScintRes.rc
+++ b/scintilla/win32/ScintRes.rc
@@ -6,8 +6,8 @@
 
 #include <windows.h>
 
-#define VERSION_SCINTILLA "5.3.3"
-#define VERSION_WORDS 5, 3, 3, 0
+#define VERSION_SCINTILLA "5.3.4"
+#define VERSION_WORDS 5, 3, 4, 0
 
 VS_VERSION_INFO VERSIONINFO
 FILEVERSION	VERSION_WORDS