5 files changed, 46 insertions, 1 deletions
diff --git a/src/Editor.cxx b/src/Editor.cxx
index db7e2366e..bd2742539 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -117,7 +117,7 @@ static constexpr bool IsAllSpacesOrTabs(std::string_view sv) noexcept {
 	return true;
 }
 
-Editor::Editor() : durationWrapOneByte(0.000001, 0.0000001, 0.00001) {
+Editor::Editor() : durationWrapOneByte(0.000001, 0.00000001, 0.00001) {
 	ctrlID = 0;
 
 	stylesValid = false;
@@ -5748,6 +5748,9 @@ void Editor::StyleSetMessage(Message iMessage, uptr_t wParam, sptr_t lParam) {
 	case Message::StyleSetHotSpot:
 		vs.styles[wParam].hotspot = lParam != 0;
 		break;
+	case Message::StyleSetCheckMonospaced:
+		vs.styles[wParam].checkMonospaced = lParam != 0;
+		break;
 	default:
 		break;
 	}
@@ -5787,6 +5790,8 @@ sptr_t Editor::StyleGetMessage(Message iMessage, uptr_t wParam, sptr_t lParam) {
 		return vs.styles[wParam].changeable ? 1 : 0;
 	case Message::StyleGetHotSpot:
 		return vs.styles[wParam].hotspot ? 1 : 0;
+	case Message::StyleGetCheckMonospaced:
+		return vs.styles[wParam].checkMonospaced ? 1 : 0;
 	default:
 		break;
 	}
@@ -7202,6 +7207,7 @@ sptr_t Editor::WndProc(Message iMessage, uptr_t wParam, sptr_t lParam) {
 	case Message::StyleSetVisible:
 	case Message::StyleSetChangeable:
 	case Message::StyleSetHotSpot:
+	case Message::StyleSetCheckMonospaced:
 		StyleSetMessage(iMessage, wParam, lParam);
 		break;
 
@@ -7220,6 +7226,7 @@ sptr_t Editor::WndProc(Message iMessage, uptr_t wParam, sptr_t lParam) {
 	case Message::StyleGetVisible:
 	case Message::StyleGetChangeable:
 	case Message::StyleGetHotSpot:
+	case Message::StyleGetCheckMonospaced:
 		return StyleGetMessage(iMessage, wParam, lParam);
 
 	case Message::StyleResetDefault:
diff --git a/src/PositionCache.cxx b/src/PositionCache.cxx
index 714937dc1..fda736cc7 100644
--- a/src/PositionCache.cxx
+++ b/src/PositionCache.cxx
@@ -377,6 +377,14 @@ constexpr size_t AlignUp(size_t value, size_t alignment) noexcept {
 
 constexpr size_t alignmentLLC = 20;
 
+constexpr bool GraphicASCII(char ch) noexcept {
+	return ch >= ' ' && ch <= '~';
+}
+
+bool AllGraphicASCII(std::string_view text) noexcept {
+	return std::all_of(text.cbegin(), text.cend(), GraphicASCII);
+}
+
 }
 
 
@@ -895,6 +903,14 @@ void PositionCache::MeasureWidths(Surface *surface, const ViewStyle &vstyle, uns
 			probe = probe2;
 		}
 	}
+	if (vstyle.styles[styleNumber].monospaceASCII) {
+		if (AllGraphicASCII(sv)) {
+			for (size_t i = 0; i < sv.length(); i++) {
+				positions[i] = vstyle.styles[styleNumber].aveCharWidth * (i+1);
+			}
+			return;
+		}
+	}
 	const Font *fontStyle = vstyle.styles[styleNumber].font.get();
 	surface->MeasureWidths(fontStyle, sv, positions);
 	if (probe < pces.size()) {
diff --git a/src/Style.cxx b/src/Style.cxx
index d71b62d97..3a57d1a08 100644
--- a/src/Style.cxx
+++ b/src/Style.cxx
@@ -57,6 +57,7 @@ void FontMeasurements::ClearMeasurements() noexcept {
 	capitalHeight = 1;
 	aveCharWidth = 1;
 	spaceWidth = 1;
+	monospaceASCII = false;
 	sizeZoomed = 2;
 }
 
diff --git a/src/Style.h b/src/Style.h
index 8153d156e..087b13b2f 100644
--- a/src/Style.h
+++ b/src/Style.h
@@ -17,6 +17,7 @@ struct FontSpecification {
 	int size;
 	Scintilla::CharacterSet characterSet;
 	Scintilla::FontQuality extraFontFlag;
+	bool checkMonospaced = false;
 	FontSpecification() noexcept :
 		fontName(nullptr),
 		weight(Scintilla::FontWeight::Normal),
@@ -35,6 +36,7 @@ struct FontMeasurements {
 	XYPOSITION capitalHeight;	// Top of capital letter to baseline: ascent - internal leading
 	XYPOSITION aveCharWidth;
 	XYPOSITION spaceWidth;
+	bool monospaceASCII = false;
 	int sizeZoomed;
 	FontMeasurements() noexcept;
 	void ClearMeasurements() noexcept;
diff --git a/src/ViewStyle.cxx b/src/ViewStyle.cxx
index 33b861445..47f76d357 100644
--- a/src/ViewStyle.cxx
+++ b/src/ViewStyle.cxx
@@ -18,6 +18,7 @@
 #include <optional>
 #include <algorithm>
 #include <memory>
+#include <numeric>
 
 #include "ScintillaTypes.h"
 
@@ -64,6 +65,24 @@ void FontRealised::Realise(Surface &surface, int zoomLevel, Technology technolog
 	capitalHeight = surface.Ascent(font.get()) - surface.InternalLeading(font.get());
 	aveCharWidth = surface.AverageCharWidth(font.get());
 	spaceWidth = surface.WidthText(font.get(), " ");
+
+	if (fs.checkMonospaced) {
+		std::string allASCIIGraphic("Ayfi");	// "Ay" is normally strongly kerned and "fi" may be a ligature
+		for (unsigned char ch = 0x20; ch <= 0x7E; ch++) {
+			allASCIIGraphic.push_back(ch);
+		}
+		std::vector<XYPOSITION> positions(allASCIIGraphic.length());
+		surface.MeasureWidths(font.get(), allASCIIGraphic, positions.data());
+		std::adjacent_difference(positions.begin(), positions.end(), positions.begin());
+		const XYPOSITION maxWidth = *std::max_element(positions.begin(), positions.end());
+		const XYPOSITION minWidth = *std::min_element(positions.begin(), positions.end());
+		const XYPOSITION variance = maxWidth - minWidth;
+		const XYPOSITION scaledVariance = variance / aveCharWidth;
+		constexpr XYPOSITION monospaceWidthEpsilon = 0.000001;	// May need tweaking if monospace fonts vary more
+		monospaceASCII = scaledVariance < monospaceWidthEpsilon;
+	} else {
+		monospaceASCII = false;
+	}
 }
 
 ViewStyle::ViewStyle() : markers(MarkerMax + 1), indicators(static_cast<size_t>(IndicatorNumbers::Max) + 1) {