Feature [feature-requests:#1402]. Unify colour type with ColourAlpha.

Change ColourDesired to ColourAlpha in styles.
Remove ColourDesired.

16 files changed, 251 insertions, 272 deletions

diff --git a/src/CallTip.cxx b/src/CallTip.cxx
index f9f3ce7f7..56cf3c2fd 100644
--- a/src/CallTip.cxx
+++ b/src/CallTip.cxx
@@ -54,15 +54,15 @@ CallTip::CallTip() noexcept {
 
 #ifdef __APPLE__
 	// proper apple colours for the default
-	colourBG = ColourDesired(0xff, 0xff, 0xc6);
-	colourUnSel = ColourDesired(0, 0, 0);
+	colourBG = ColourAlpha(0xff, 0xff, 0xc6);
+	colourUnSel = ColourAlpha(0, 0, 0);
 #else
-	colourBG = ColourDesired(0xff, 0xff, 0xff);
-	colourUnSel = ColourDesired(0x80, 0x80, 0x80);
+	colourBG = ColourAlpha(0xff, 0xff, 0xff);
+	colourUnSel = ColourAlpha(0x80, 0x80, 0x80);
 #endif
-	colourSel = ColourDesired(0, 0, 0x80);
-	colourShade = ColourDesired(0, 0, 0);
-	colourLight = ColourDesired(0xc0, 0xc0, 0xc0);
+	colourSel = ColourAlpha(0, 0, 0x80);
+	colourShade = ColourAlpha(0, 0, 0);
+	colourLight = ColourAlpha(0xc0, 0xc0, 0xc0);
 	codePage = 0;
 	clickPlace = 0;
 }
@@ -93,7 +93,7 @@ constexpr bool IsArrowCharacter(char ch) noexcept {
 	return (ch == 0) || (ch == '\001') || (ch == '\002');
 }
 
-void DrawArrow(Scintilla::Surface *surface, const PRectangle &rc, bool upArrow, ColourDesired colourBG, ColourDesired colourUnSel) {
+void DrawArrow(Scintilla::Surface *surface, const PRectangle &rc, bool upArrow, ColourAlpha colourBG, ColourAlpha colourUnSel) {
 	surface->FillRectangle(rc, colourBG);
 	const PRectangle rcClientInner = Clamp(rc.Inset(1), Edge::right, rc.right - 2);
 	surface->FillRectangle(rcClientInner, colourUnSel);
@@ -348,7 +348,7 @@ bool CallTip::UseStyleCallTip() const noexcept {
 
 // It might be better to have two access functions for this and to use
 // them for all settings of colours.
-void CallTip::SetForeBack(const ColourDesired &fore, const ColourDesired &back) noexcept {
+void CallTip::SetForeBack(const ColourAlpha &fore, const ColourAlpha &back) noexcept {
 	colourBG = back;
 	colourUnSel = fore;
 }
diff --git a/src/CallTip.h b/src/CallTip.h
index f1358a94a..78518a995 100644
--- a/src/CallTip.h
+++ b/src/CallTip.h
@@ -44,11 +44,11 @@ public:
 	Window wDraw;
 	bool inCallTipMode;
 	Sci::Position posStartCallTip;
-	ColourDesired colourBG;
-	ColourDesired colourUnSel;
-	ColourDesired colourSel;
-	ColourDesired colourShade;
-	ColourDesired colourLight;
+	ColourAlpha colourBG;
+	ColourAlpha colourUnSel;
+	ColourAlpha colourSel;
+	ColourAlpha colourShade;
+	ColourAlpha colourLight;
 	int codePage;
 	int clickPlace;
 
@@ -91,7 +91,7 @@ public:
 	bool UseStyleCallTip() const noexcept;
 
 	// Modify foreground and background colours
-	void SetForeBack(const ColourDesired &fore, const ColourDesired &back) noexcept;
+	void SetForeBack(const ColourAlpha &fore, const ColourAlpha &back) noexcept;
 };
 
 }
diff --git a/src/EditView.cxx b/src/EditView.cxx
index c5e3a3726..fbb6f8b5c 100644
--- a/src/EditView.cxx
+++ b/src/EditView.cxx
@@ -820,20 +820,20 @@ Sci::Position EditView::StartEndDisplayLine(Surface *surface, const EditModel &m
 	return posRet;
 }
 
-static ColourDesired SelectionBackground(const ViewStyle &vsDraw, bool main, bool primarySelection) noexcept {
+static ColourAlpha SelectionBackground(const ViewStyle &vsDraw, bool main, bool primarySelection) noexcept {
 	return main ?
-		(primarySelection ? vsDraw.selColours.back : vsDraw.selBackground2) :
+		(primarySelection ? vsDraw.selColours.back.value() : vsDraw.selBackground2) :
 		vsDraw.selAdditionalBackground;
 }
 
-static ColourDesired TextBackground(const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
-	ColourOptional background, int inSelection, bool inHotspot, int styleMain, Sci::Position i) noexcept {
+static ColourAlpha TextBackground(const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
+	std::optional<ColourAlpha> background, int inSelection, bool inHotspot, int styleMain, Sci::Position i) noexcept {
 	if (inSelection == 1) {
-		if (vsDraw.selColours.back.isSet && (vsDraw.selAlpha == SC_ALPHA_NOALPHA)) {
+		if (vsDraw.selColours.back && (vsDraw.selAlpha == SC_ALPHA_NOALPHA)) {
 			return SelectionBackground(vsDraw, true, model.primarySelection);
 		}
 	} else if (inSelection == 2) {
-		if (vsDraw.selColours.back.isSet && (vsDraw.selAdditionalAlpha == SC_ALPHA_NOALPHA)) {
+		if (vsDraw.selColours.back && (vsDraw.selAdditionalAlpha == SC_ALPHA_NOALPHA)) {
 			return SelectionBackground(vsDraw, false, model.primarySelection);
 		}
 	} else {
@@ -841,11 +841,11 @@ static ColourDesired TextBackground(const EditModel &model, const ViewStyle &vsD
 			(i >= ll->edgeColumn) &&
 			(i < ll->numCharsBeforeEOL))
 			return vsDraw.theEdge.colour;
-		if (inHotspot && vsDraw.hotspotColours.back.isSet)
-			return vsDraw.hotspotColours.back;
+		if (inHotspot && vsDraw.hotspotColours.back)
+			return vsDraw.hotspotColours.back.value();
 	}
-	if (background.isSet && (styleMain != STYLE_BRACELIGHT) && (styleMain != STYLE_BRACEBAD)) {
-		return background;
+	if (background && (styleMain != STYLE_BRACELIGHT) && (styleMain != STYLE_BRACEBAD)) {
+		return background.value();
 	} else {
 		return vsDraw.styles[styleMain].back;
 	}
@@ -859,14 +859,14 @@ void EditView::DrawIndentGuide(Surface *surface, Sci::Line lineVisible, int line
 		highlight ? *pixmapIndentGuideHighlight : *pixmapIndentGuide);
 }
 
-static void SimpleAlphaRectangle(Surface *surface, PRectangle rc, ColourDesired fill, int alpha) {
+static void SimpleAlphaRectangle(Surface *surface, PRectangle rc, ColourAlpha fill, int alpha) {
 	if (alpha != SC_ALPHA_NOALPHA) {
 		surface->FillRectangleAligned(rc, ColourAlpha(fill, alpha));
 	}
 }
 
 static void DrawTextBlob(Surface *surface, const ViewStyle &vsDraw, PRectangle rcSegment,
-	std::string_view text, ColourDesired textBack, ColourDesired textFore, bool fillBackground) {
+	std::string_view text, ColourAlpha textBack, ColourAlpha textFore, bool fillBackground) {
 	if (rcSegment.Empty())
 		return;
 	if (fillBackground) {
@@ -890,7 +890,7 @@ static void DrawTextBlob(Surface *surface, const ViewStyle &vsDraw, PRectangle r
 		textBack, textFore);
 }
 
-static void DrawFrame(Surface *surface, ColourDesired colour, int alpha, PRectangle rcFrame) {
+static void DrawFrame(Surface *surface, ColourAlpha colour, int alpha, PRectangle rcFrame) {
 	if (alpha != SC_ALPHA_NOALPHA) {
 		surface->AlphaRectangle(rcFrame, 0, FillStroke(ColourAlpha(colour, alpha)));
 	} else {
@@ -924,7 +924,7 @@ static void DrawCaretLineFramed(Surface *surface, const ViewStyle &vsDraw, const
 
 void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
 	PRectangle rcLine, Sci::Line line, Sci::Position lineEnd, int xStart, int subLine, XYACCUMULATOR subLineStart,
-	ColourOptional background) {
+	std::optional<ColourAlpha> background) {
 
 	const Sci::Position posLineStart = model.pdoc->LineStart(line);
 	PRectangle rcSegment = rcLine;
@@ -941,7 +941,7 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 	if (virtualSpace > 0.0f) {
 		rcSegment.left = xEol + xStart;
 		rcSegment.right = xEol + xStart + virtualSpace;
-		surface->FillRectangleAligned(rcSegment, Fill(background.isSet ? background : vsDraw.styles[ll->styles[ll->numCharsInLine]].back));
+		surface->FillRectangleAligned(rcSegment, Fill(background ? background.value() : vsDraw.styles[ll->styles[ll->numCharsInLine]].back));
 		if (!hideSelection && ((vsDraw.selAlpha == SC_ALPHA_NOALPHA) || (vsDraw.selAdditionalAlpha == SC_ALPHA_NOALPHA))) {
 			const SelectionSegment virtualSpaceRange(SelectionPosition(model.pdoc->LineEnd(line)),
 				SelectionPosition(model.pdoc->LineEnd(line),
@@ -984,7 +984,7 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 			const char *ctrlChar;
 			const unsigned char chEOL = ll->chars[eolPos];
 			const int styleMain = ll->styles[eolPos];
-			const ColourDesired textBack = TextBackground(model, vsDraw, ll, background, eolInSelection, false, styleMain, eolPos);
+			const ColourAlpha textBack = TextBackground(model, vsDraw, ll, background, eolInSelection, false, styleMain, eolPos);
 			if (UTF8IsAscii(chEOL)) {
 				ctrlChar = ControlCharacterString(chEOL);
 			} else {
@@ -997,11 +997,11 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 					ctrlChar = hexits;
 				}
 			}
-			ColourDesired textFore = vsDraw.styles[styleMain].fore;
-			if (eolInSelection && vsDraw.selColours.fore.isSet) {
-				textFore = (eolInSelection == 1) ? vsDraw.selColours.fore : vsDraw.selAdditionalForeground;
+			ColourAlpha textFore = vsDraw.styles[styleMain].fore;
+			if (eolInSelection && vsDraw.selColours.fore) {
+				textFore = (eolInSelection == 1) ? vsDraw.selColours.fore.value() : vsDraw.selAdditionalForeground;
 			}
-			if (eolInSelection && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1)) {
+			if (eolInSelection && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1)) {
 				if (alpha == SC_ALPHA_NOALPHA) {
 					surface->FillRectangleAligned(rcSegment, Fill(SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection)));
 				} else {
@@ -1011,7 +1011,7 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 				surface->FillRectangleAligned(rcSegment, Fill(textBack));
 			}
 			DrawTextBlob(surface, vsDraw, rcSegment, ctrlChar, textBack, textFore, phasesDraw == PhasesDraw::one);
-			if (eolInSelection && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
+			if (eolInSelection && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
 				SimpleAlphaRectangle(surface, rcSegment, SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection), alpha);
 			}
 		}
@@ -1021,11 +1021,11 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 	rcSegment.left = xEol + xStart + virtualSpace + blobsWidth;
 	rcSegment.right = rcSegment.left + vsDraw.aveCharWidth;
 
-	if (eolInSelection && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && (alpha == SC_ALPHA_NOALPHA)) {
+	if (eolInSelection && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && (alpha == SC_ALPHA_NOALPHA)) {
 		surface->FillRectangleAligned(rcSegment, Fill(SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection)));
 	} else {
-		if (background.isSet) {
-			surface->FillRectangleAligned(rcSegment, Fill(background));
+		if (background) {
+			surface->FillRectangleAligned(rcSegment, Fill(background.value()));
 		} else if (line < model.pdoc->LinesTotal() - 1) {
 			surface->FillRectangleAligned(rcSegment, Fill(vsDraw.styles[ll->styles[ll->numCharsInLine]].back));
 		} else if (vsDraw.styles[ll->styles[ll->numCharsInLine]].eolFilled) {
@@ -1033,7 +1033,7 @@ void EditView::DrawEOL(Surface *surface, const EditModel &model, const ViewStyle
 		} else {
 			surface->FillRectangleAligned(rcSegment, Fill(vsDraw.styles[STYLE_DEFAULT].back));
 		}
-		if (eolInSelection && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
+		if (eolInSelection && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
 			SimpleAlphaRectangle(surface, rcSegment, SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection), alpha);
 		}
 	}
@@ -1215,12 +1215,12 @@ void EditView::DrawFoldDisplayText(Surface *surface, const EditModel &model, con
 	rcSegment.left = xStart + static_cast<XYPOSITION>(ll->positions[ll->numCharsInLine] - subLineStart) + virtualSpace + vsDraw.aveCharWidth;
 	rcSegment.right = rcSegment.left + static_cast<XYPOSITION>(widthFoldDisplayText);
 
-	const ColourOptional background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
-	ColourDesired textFore = vsDraw.styles[STYLE_FOLDDISPLAYTEXT].fore;
-	if (eolInSelection && (vsDraw.selColours.fore.isSet)) {
-		textFore = (eolInSelection == 1) ? vsDraw.selColours.fore : vsDraw.selAdditionalForeground;
+	const std::optional<ColourAlpha> background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
+	ColourAlpha textFore = vsDraw.styles[STYLE_FOLDDISPLAYTEXT].fore;
+	if (eolInSelection && (vsDraw.selColours.fore)) {
+		textFore = (eolInSelection == 1) ? vsDraw.selColours.fore.value() : vsDraw.selAdditionalForeground;
 	}
-	const ColourDesired textBack = TextBackground(model, vsDraw, ll, background, eolInSelection,
+	const ColourAlpha textBack = TextBackground(model, vsDraw, ll, background, eolInSelection,
 											false, STYLE_FOLDDISPLAYTEXT, -1);
 
 	if (model.trackLineWidth) {
@@ -1264,7 +1264,7 @@ void EditView::DrawFoldDisplayText(Surface *surface, const EditModel &model, con
 	}
 
 	if (FlagSet(phase, DrawPhase::selectionTranslucent)) {
-		if (eolInSelection && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && alpha != SC_ALPHA_NOALPHA) {
+		if (eolInSelection && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && alpha != SC_ALPHA_NOALPHA) {
 			SimpleAlphaRectangle(surface, rcSegment, SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection), alpha);
 		}
 	}
@@ -1342,9 +1342,9 @@ void EditView::DrawEOLAnnotationText(Surface *surface, const EditModel &model, c
 	}
 	rcSegment.right = rcSegment.left + static_cast<XYPOSITION>(widthEOLAnnotationText);
 
-	const ColourOptional background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
-	const ColourDesired textFore = vsDraw.styles[style].fore;
-	const ColourDesired textBack = TextBackground(model, vsDraw, ll, background, false,
+	const std::optional<ColourAlpha> background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
+	const ColourAlpha textFore = vsDraw.styles[style].fore;
+	const ColourAlpha textBack = TextBackground(model, vsDraw, ll, background, false,
 											false, static_cast<int>(style), -1);
 
 	if (model.trackLineWidth) {
@@ -1388,10 +1388,10 @@ void EditView::DrawEOLAnnotationText(Surface *surface, const EditModel &model, c
 			} else {
 				if (phasesDraw == PhasesDraw::one) {
 					// Draw an outline around the text
-					surface->Stadium(rcBox, FillStroke(ColourAlpha(textBack, 0), ColourAlpha(textFore), 1.0), ends);
+					surface->Stadium(rcBox, FillStroke(ColourAlpha(textBack, 0), textFore, 1.0), ends);
 				} else {
 					// Draw with a fill to fill the edges of the shape.
-					surface->Stadium(rcBox, FillStroke(ColourAlpha(textBack), ColourAlpha(textFore), 1.0), ends);
+					surface->Stadium(rcBox, FillStroke(textBack, textFore, 1.0), ends);
 				}
 			}
 		}
@@ -1451,7 +1451,7 @@ void EditView::DrawAnnotation(Surface *surface, const EditModel &model, const Vi
 		DrawStyledText(surface, vsDraw, vsDraw.annotationStyleOffset, rcText,
 			stAnnotation, start, lengthAnnotation, phase);
 		if ((FlagSet(phase, DrawPhase::back)) && (vsDraw.annotationVisible == ANNOTATION_BOXED)) {
-			const ColourDesired colourBorder = vsDraw.styles[vsDraw.annotationStyleOffset].fore;
+			const ColourAlpha colourBorder = vsDraw.styles[vsDraw.annotationStyleOffset].fore;
 			const PRectangle rcBorder = PixelAlignOutside(rcSegment, surface->PixelDivisions());
 			surface->FillRectangle(Side(rcBorder, Edge::left, 1), colourBorder);
 			surface->FillRectangle(Side(rcBorder, Edge::right, 1), colourBorder);
@@ -1466,7 +1466,7 @@ void EditView::DrawAnnotation(Surface *surface, const EditModel &model, const Vi
 }
 
 static void DrawBlockCaret(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
-	int subLine, int xStart, Sci::Position offset, Sci::Position posCaret, PRectangle rcCaret, ColourDesired caretColour) {
+	int subLine, int xStart, Sci::Position offset, Sci::Position posCaret, PRectangle rcCaret, ColourAlpha caretColour) {
 
 	const Sci::Position lineStart = ll->LineStart(subLine);
 	Sci::Position posBefore = posCaret;
@@ -1622,7 +1622,8 @@ void EditView::DrawCarets(Surface *surface, const EditModel &model, const ViewSt
 					rcCaret.left = std::round(xposCaret - caretWidthOffset);
 					rcCaret.right = rcCaret.left + vsDraw.caretWidth;
 				}
-				const ColourDesired caretColour = mainCaret ? vsDraw.caretcolour : vsDraw.additionalCaretColour;
+				const ColourAlpha caretColour = mainCaret ? vsDraw.caretcolour : vsDraw.additionalCaretColour;
+				assert(caretColour.IsOpaque());
 				if (drawBlockCaret) {
 					DrawBlockCaret(surface, model, vsDraw, ll, subLine, xStart, offset, posCaret.Position(), rcCaret, caretColour);
 				} else {
@@ -1636,10 +1637,10 @@ void EditView::DrawCarets(Surface *surface, const EditModel &model, const ViewSt
 }
 
 static void DrawWrapIndentAndMarker(Surface *surface, const ViewStyle &vsDraw, const LineLayout *ll,
-	int xStart, PRectangle rcLine, ColourOptional background, DrawWrapMarkerFn customDrawWrapMarker,
+	int xStart, PRectangle rcLine, std::optional<ColourAlpha> background, DrawWrapMarkerFn customDrawWrapMarker,
 	bool caretActive) {
 	// default bgnd here..
-	surface->FillRectangleAligned(rcLine, Fill(background.isSet ? background :
+	surface->FillRectangleAligned(rcLine, Fill(background ? background.value() :
 		vsDraw.styles[STYLE_DEFAULT].back));
 
 	if (vsDraw.IsLineFrameOpaque(caretActive, ll->containsCaret)) {
@@ -1672,7 +1673,7 @@ static void DrawWrapIndentAndMarker(Surface *surface, const ViewStyle &vsDraw, c
 
 void EditView::DrawBackground(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
 	PRectangle rcLine, Range lineRange, Sci::Position posLineStart, int xStart,
-	int subLine, ColourOptional background) const {
+	int subLine, std::optional<ColourAlpha> background) const {
 
 	const bool selBackDrawn = vsDraw.SelectionBackgroundDrawn();
 	bool inIndentation = subLine == 0;	// Do not handle indentation except on first subline.
@@ -1682,7 +1683,7 @@ void EditView::DrawBackground(Surface *surface, const EditModel &model, const Vi
 
 	BreakFinder bfBack(ll, &model.sel, lineRange, posLineStart, xStartVisible, selBackDrawn, model.pdoc, &model.reprs, nullptr);
 
-	const bool drawWhitespaceBackground = vsDraw.WhitespaceBackgroundDrawn() && !background.isSet;
+	const bool drawWhitespaceBackground = vsDraw.WhitespaceBackgroundDrawn() && !background;
 
 	// Background drawing loop
 	while (bfBack.More()) {
@@ -1705,13 +1706,13 @@ void EditView::DrawBackground(Surface *surface, const EditModel &model, const Vi
 
 			const int inSelection = hideSelection ? 0 : model.sel.CharacterInSelection(iDoc);
 			const bool inHotspot = (ll->hotspot.Valid()) && ll->hotspot.ContainsCharacter(iDoc);
-			ColourDesired textBack = TextBackground(model, vsDraw, ll, background, inSelection,
+			ColourAlpha textBack = TextBackground(model, vsDraw, ll, background, inSelection,
 				inHotspot, ll->styles[i], i);
 			if (ts.representation) {
 				if (ll->chars[i] == '\t') {
 					// Tab display
 					if (drawWhitespaceBackground && vsDraw.WhiteSpaceVisible(inIndentation))
-						textBack = vsDraw.whitespaceColours.back;
+						textBack = vsDraw.whitespaceColours.back.value();
 				} else {
 					// Blob display
 					inIndentation = false;
@@ -1729,7 +1730,7 @@ void EditView::DrawBackground(Surface *surface, const EditModel &model, const Vi
 									rcSegment.top,
 									ll->positions[cpos + ts.start + 1] + xStart - static_cast<XYPOSITION>(subLineStart),
 									rcSegment.bottom);
-								surface->FillRectangleAligned(rcSpace, Fill(vsDraw.whitespaceColours.back));
+								surface->FillRectangleAligned(rcSpace, Fill(vsDraw.whitespaceColours.back.value()));
 							}
 						} else {
 							inIndentation = false;
@@ -1806,7 +1807,7 @@ static void DrawTranslucentSelection(Surface *surface, const EditModel &model, c
 						const int selectionStart = static_cast<int>(portion.start.Position() - posLineStart - lineRange.start);
 						const int selectionEnd = static_cast<int>(portion.end.Position() - posLineStart - lineRange.start);
 
-						const ColourDesired background = SelectionBackground(vsDraw, r == model.sel.Main(), model.primarySelection);
+						const ColourAlpha background = SelectionBackground(vsDraw, r == model.sel.Main(), model.primarySelection);
 
 						const ScreenLine screenLine(ll, subLine, vsDraw, rcLine.right, tabWidthMinimumPixels);
 						std::unique_ptr<IScreenLineLayout> slLayout = surface->Layout(&screenLine);
@@ -1884,10 +1885,10 @@ static void DrawTranslucentLineState(Surface *surface, const EditModel &model, c
 
 void EditView::DrawForeground(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
 	Sci::Line lineVisible, PRectangle rcLine, Range lineRange, Sci::Position posLineStart, int xStart,
-	int subLine, ColourOptional background) {
+	int subLine, std::optional<ColourAlpha> background) {
 
 	const bool selBackDrawn = vsDraw.SelectionBackgroundDrawn();
-	const bool drawWhitespaceBackground = vsDraw.WhitespaceBackgroundDrawn() && !background.isSet;
+	const bool drawWhitespaceBackground = vsDraw.WhitespaceBackgroundDrawn() && !background;
 	bool inIndentation = subLine == 0;	// Do not handle indentation except on first subline.
 
 	const XYACCUMULATOR subLineStart = ll->positions[lineRange.start];
@@ -1898,7 +1899,7 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 
 	// Foreground drawing loop
 	BreakFinder bfFore(ll, &model.sel, lineRange, posLineStart, xStartVisible,
-		(((phasesDraw == PhasesDraw::one) && selBackDrawn) || vsDraw.selColours.fore.isSet), model.pdoc, &model.reprs, &vsDraw);
+		(((phasesDraw == PhasesDraw::one) && selBackDrawn) || vsDraw.selColours.fore), model.pdoc, &model.reprs, &vsDraw);
 
 	while (bfFore.More()) {
 
@@ -1913,13 +1914,13 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 		// draw strings that are completely past the right side of the window.
 		if (rcSegment.Intersects(rcLine)) {
 			const int styleMain = ll->styles[i];
-			ColourDesired textFore = vsDraw.styles[styleMain].fore;
+			ColourAlpha textFore = vsDraw.styles[styleMain].fore;
 			const Font *textFont = vsDraw.styles[styleMain].font.get();
 			//hotspot foreground
 			const bool inHotspot = (ll->hotspot.Valid()) && ll->hotspot.ContainsCharacter(iDoc);
 			if (inHotspot) {
-				if (vsDraw.hotspotColours.fore.isSet)
-					textFore = vsDraw.hotspotColours.fore;
+				if (vsDraw.hotspotColours.fore)
+					textFore = vsDraw.hotspotColours.fore.value();
 			}
 			if (vsDraw.indicatorsSetFore) {
 				// At least one indicator sets the text colour so see if it applies to this segment
@@ -1940,7 +1941,7 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 						} else {
 							if (indicator.sacNormal.style == INDIC_TEXTFORE) {
 								if (indicator.Flags() & SC_INDICFLAG_VALUEFORE)
-									textFore = ColourDesired(indicatorValue & SC_INDICVALUEMASK);
+									textFore = ColourAlpha::FromRGB(indicatorValue & SC_INDICVALUEMASK);
 								else
 									textFore = indicator.sacNormal.fore;
 							}
@@ -1949,16 +1950,16 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 				}
 			}
 			const int inSelection = hideSelection ? 0 : model.sel.CharacterInSelection(iDoc);
-			if (inSelection && (vsDraw.selColours.fore.isSet)) {
-				textFore = (inSelection == 1) ? vsDraw.selColours.fore : vsDraw.selAdditionalForeground;
+			if (inSelection && (vsDraw.selColours.fore)) {
+				textFore = (inSelection == 1) ? vsDraw.selColours.fore.value() : vsDraw.selAdditionalForeground;
 			}
-			ColourDesired textBack = TextBackground(model, vsDraw, ll, background, inSelection, inHotspot, styleMain, i);
+			ColourAlpha textBack = TextBackground(model, vsDraw, ll, background, inSelection, inHotspot, styleMain, i);
 			if (ts.representation) {
 				if (ll->chars[i] == '\t') {
 					// Tab display
 					if (phasesDraw == PhasesDraw::one) {
 						if (drawWhitespaceBackground && vsDraw.WhiteSpaceVisible(inIndentation))
-							textBack = vsDraw.whitespaceColours.back;
+							textBack = vsDraw.whitespaceColours.back.value();
 						surface->FillRectangleAligned(rcSegment, Fill(textBack));
 					}
 					if (inIndentation && vsDraw.viewIndentationGuides == IndentView::real) {
@@ -1974,8 +1975,8 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 					}
 					if (vsDraw.viewWhitespace != WhiteSpace::invisible) {
 						if (vsDraw.WhiteSpaceVisible(inIndentation)) {
-							if (vsDraw.whitespaceColours.fore.isSet)
-								textFore = vsDraw.whitespaceColours.fore;
+							if (vsDraw.whitespaceColours.fore)
+								textFore = vsDraw.whitespaceColours.fore.value();
 							const PRectangle rcTab(rcSegment.left + 1, rcSegment.top + tabArrowHeight,
 								rcSegment.right - 1, rcSegment.bottom - vsDraw.maxDescent);
 							const int segmentTop = static_cast<int>(rcSegment.top + vsDraw.lineHeight / 2);
@@ -2018,12 +2019,12 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 					for (int cpos = 0; cpos <= i - ts.start; cpos++) {
 						if (ll->chars[cpos + ts.start] == ' ') {
 							if (vsDraw.viewWhitespace != WhiteSpace::invisible) {
-								if (vsDraw.whitespaceColours.fore.isSet)
-									textFore = vsDraw.whitespaceColours.fore;
+								if (vsDraw.whitespaceColours.fore)
+									textFore = vsDraw.whitespaceColours.fore.value();
 								if (vsDraw.WhiteSpaceVisible(inIndentation)) {
 									const XYPOSITION xmid = (ll->positions[cpos + ts.start] + ll->positions[cpos + ts.start + 1]) / 2;
 									if ((phasesDraw == PhasesDraw::one) && drawWhitespaceBackground) {
-										textBack = vsDraw.whitespaceColours.back;
+										textBack = vsDraw.whitespaceColours.back.value();
 										const PRectangle rcSpace(
 											ll->positions[cpos + ts.start] + xStart - static_cast<XYPOSITION>(subLineStart),
 											rcSegment.top,
@@ -2060,8 +2061,8 @@ void EditView::DrawForeground(Surface *surface, const EditModel &model, const Vi
 				PRectangle rcUL = rcSegment;
 				rcUL.top = rcUL.top + vsDraw.maxAscent + 1;
 				rcUL.bottom = rcUL.top + 1;
-				if (vsDraw.hotspotColours.fore.isSet)
-					surface->FillRectangleAligned(rcUL, Fill(vsDraw.hotspotColours.fore));
+				if (vsDraw.hotspotColours.fore)
+					surface->FillRectangleAligned(rcUL, Fill(vsDraw.hotspotColours.fore.value()));
 				else
 					surface->FillRectangleAligned(rcUL, Fill(textFore));
 			} else if (vsDraw.styles[styleMain].underline) {
@@ -2139,7 +2140,7 @@ void EditView::DrawLine(Surface *surface, const EditModel &model, const ViewStyl
 	}
 
 	// See if something overrides the line background colour.
-	const ColourOptional background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
+	const std::optional<ColourAlpha> background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
 
 	const Sci::Position posLineStart = model.pdoc->LineStart(line);
 
@@ -2445,19 +2446,19 @@ void EditView::FillLineRemainder(Surface *surface, const EditModel &model, const
 			alpha = (eolInSelection == 1) ? vsDraw.selAlpha : vsDraw.selAdditionalAlpha;
 		}
 
-		const ColourOptional background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
+		const std::optional<ColourAlpha> background = vsDraw.Background(model.pdoc->GetMark(line), model.caret.active, ll->containsCaret);
 
-		if (eolInSelection && vsDraw.selEOLFilled && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && (alpha == SC_ALPHA_NOALPHA)) {
+		if (eolInSelection && vsDraw.selEOLFilled && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && (alpha == SC_ALPHA_NOALPHA)) {
 			surface->FillRectangleAligned(rcArea, Fill(SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection)));
 		} else {
-			if (background.isSet) {
-				surface->FillRectangleAligned(rcArea, Fill(background));
+			if (background) {
+				surface->FillRectangleAligned(rcArea, Fill(background.value()));
 			} else if (vsDraw.styles[ll->styles[ll->numCharsInLine]].eolFilled) {
 				surface->FillRectangleAligned(rcArea, Fill(vsDraw.styles[ll->styles[ll->numCharsInLine]].back));
 			} else {
 				surface->FillRectangleAligned(rcArea, Fill(vsDraw.styles[STYLE_DEFAULT].back));
 			}
-			if (eolInSelection && vsDraw.selEOLFilled && vsDraw.selColours.back.isSet && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
+			if (eolInSelection && vsDraw.selEOLFilled && vsDraw.selColours.back && (line < model.pdoc->LinesTotal() - 1) && (alpha != SC_ALPHA_NOALPHA)) {
 				SimpleAlphaRectangle(surface, rcArea, SelectionBackground(vsDraw, eolInSelection == 1, model.primarySelection), alpha);
 			}
 		}
@@ -2466,18 +2467,18 @@ void EditView::FillLineRemainder(Surface *surface, const EditModel &model, const
 // Space (3 space characters) between line numbers and text when printing.
 #define lineNumberPrintSpace "   "
 
-static ColourDesired InvertedLight(ColourDesired orig) noexcept {
+static ColourAlpha InvertedLight(ColourAlpha orig) noexcept {
 	unsigned int r = orig.GetRed();
 	unsigned int g = orig.GetGreen();
 	unsigned int b = orig.GetBlue();
 	const unsigned int l = (r + g + b) / 3; 	// There is a better calculation for this that matches human eye
 	const unsigned int il = 0xff - l;
 	if (l == 0)
-		return ColourDesired(0xff, 0xff, 0xff);
+		return ColourAlpha(0xff, 0xff, 0xff);
 	r = r * il / l;
 	g = g * il / l;
 	b = b * il / l;
-	return ColourDesired(std::min(r, 0xffu), std::min(g, 0xffu), std::min(b, 0xffu));
+	return ColourAlpha(std::min(r, 0xffu), std::min(g, 0xffu), std::min(b, 0xffu));
 }
 
 Sci::Position EditView::FormatRange(bool draw, const Sci_RangeToFormat *pfr, Surface *surface, Surface *surfaceMeasure,
@@ -2504,12 +2505,12 @@ Sci::Position EditView::FormatRange(bool draw, const Sci_RangeToFormat *pfr, Sur
 	// If this ever gets changed, cached pixmap would need to be recreated if technology != SC_TECHNOLOGY_DEFAULT
 	vsPrint.viewIndentationGuides = IndentView::none;
 	// Don't show the selection when printing
-	vsPrint.selColours.back.isSet = false;
-	vsPrint.selColours.fore.isSet = false;
+	vsPrint.selColours.back.reset();
+	vsPrint.selColours.fore.reset();
 	vsPrint.selAlpha = SC_ALPHA_NOALPHA;
 	vsPrint.selAdditionalAlpha = SC_ALPHA_NOALPHA;
-	vsPrint.whitespaceColours.back.isSet = false;
-	vsPrint.whitespaceColours.fore.isSet = false;
+	vsPrint.whitespaceColours.back.reset();
+	vsPrint.whitespaceColours.fore.reset();
 	vsPrint.showCaretLineBackground = false;
 	vsPrint.alwaysShowCaretLineBackground = false;
 	// Don't highlight matching braces using indicators
@@ -2522,19 +2523,19 @@ Sci::Position EditView::FormatRange(bool draw, const Sci_RangeToFormat *pfr, Sur
 			vsPrint.styles[sty].fore = InvertedLight(vsPrint.styles[sty].fore);
 			vsPrint.styles[sty].back = InvertedLight(vsPrint.styles[sty].back);
 		} else if (printParameters.colourMode == SC_PRINT_BLACKONWHITE) {
-			vsPrint.styles[sty].fore = ColourDesired(0, 0, 0);
-			vsPrint.styles[sty].back = ColourDesired(0xff, 0xff, 0xff);
+			vsPrint.styles[sty].fore = ColourAlpha(0, 0, 0);
+			vsPrint.styles[sty].back = ColourAlpha(0xff, 0xff, 0xff);
 		} else if (printParameters.colourMode == SC_PRINT_COLOURONWHITE) {
-			vsPrint.styles[sty].back = ColourDesired(0xff, 0xff, 0xff);
+			vsPrint.styles[sty].back = ColourAlpha(0xff, 0xff, 0xff);
 		} else if (printParameters.colourMode == SC_PRINT_COLOURONWHITEDEFAULTBG) {
 			if (sty <= STYLE_DEFAULT) {
-				vsPrint.styles[sty].back = ColourDesired(0xff, 0xff, 0xff);
+				vsPrint.styles[sty].back = ColourAlpha(0xff, 0xff, 0xff);
 			}
 		}
 	}
 	// White background for the line numbers if SC_PRINT_SCREENCOLOURS isn't used
 	if (printParameters.colourMode != SC_PRINT_SCREENCOLOURS)
-		vsPrint.styles[STYLE_LINENUMBER].back = ColourDesired(0xff, 0xff, 0xff);
+		vsPrint.styles[STYLE_LINENUMBER].back = ColourAlpha(0xff, 0xff, 0xff);
 
 	// Printing uses different margins, so reset screen margins
 	vsPrint.leftMarginWidth = 0;
diff --git a/src/EditView.h b/src/EditView.h
index 91a925f4a..add58065b 100644
--- a/src/EditView.h
+++ b/src/EditView.h
@@ -131,7 +131,7 @@ public:
 	void DrawIndentGuide(Surface *surface, Sci::Line lineVisible, int lineHeight, XYPOSITION start, PRectangle rcSegment, bool highlight);
 	void DrawEOL(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll, PRectangle rcLine,
 		Sci::Line line, Sci::Position lineEnd, int xStart, int subLine, XYACCUMULATOR subLineStart,
-		ColourOptional background);
+		std::optional<ColourAlpha> background);
 	void DrawFoldDisplayText(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
 		Sci::Line line, int xStart, PRectangle rcLine, int subLine, XYACCUMULATOR subLineStart, DrawPhase phase);
 	void DrawEOLAnnotationText(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
@@ -142,10 +142,10 @@ public:
 		int xStart, PRectangle rcLine, int subLine) const;
 	void DrawBackground(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll, PRectangle rcLine,
 		Range lineRange, Sci::Position posLineStart, int xStart,
-		int subLine, ColourOptional background) const;
+		int subLine, std::optional<ColourAlpha> background) const;
 	void DrawForeground(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll, Sci::Line lineVisible,
 		PRectangle rcLine, Range lineRange, Sci::Position posLineStart, int xStart,
-		int subLine, ColourOptional background);
+		int subLine, std::optional<ColourAlpha> background);
 	void DrawIndentGuidesOverEmpty(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll,
 		Sci::Line line, Sci::Line lineVisible, PRectangle rcLine, int xStart, int subLine);
 	void DrawLine(Surface *surface, const EditModel &model, const ViewStyle &vsDraw, const LineLayout *ll, Sci::Line line,
diff --git a/src/Editor.cxx b/src/Editor.cxx
index 208a075aa..f241bf346 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -5692,10 +5692,10 @@ void Editor::StyleSetMessage(unsigned int iMessage, uptr_t wParam, sptr_t lParam
 	vs.EnsureStyle(wParam);
 	switch (iMessage) {
 	case SCI_STYLESETFORE:
-		vs.styles[wParam].fore = ColourDesired(static_cast<int>(lParam));
+		vs.styles[wParam].fore = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		break;
 	case SCI_STYLESETBACK:
-		vs.styles[wParam].back = ColourDesired(static_cast<int>(lParam));
+		vs.styles[wParam].back = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		break;
 	case SCI_STYLESETBOLD:
 		vs.styles[wParam].weight = lParam != 0 ? SC_WEIGHT_BOLD : SC_WEIGHT_NORMAL;
@@ -5747,9 +5747,9 @@ sptr_t Editor::StyleGetMessage(unsigned int iMessage, uptr_t wParam, sptr_t lPar
 	vs.EnsureStyle(wParam);
 	switch (iMessage) {
 	case SCI_STYLEGETFORE:
-		return vs.styles[wParam].fore.AsInteger();
+		return vs.styles[wParam].fore.OpaqueRGB();
 	case SCI_STYLEGETBACK:
-		return vs.styles[wParam].back.AsInteger();
+		return vs.styles[wParam].back.OpaqueRGB();
 	case SCI_STYLEGETBOLD:
 		return vs.styles[wParam].weight > SC_WEIGHT_NORMAL;
 	case SCI_STYLEGETWEIGHT:
@@ -6939,19 +6939,19 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 
 	case SCI_MARKERSETFORE:
 		if (wParam <= MARKER_MAX)
-			vs.markers[wParam].fore = ColourDesired(static_cast<int>(lParam));
+			vs.markers[wParam].fore = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		InvalidateStyleData();
 		RedrawSelMargin();
 		break;
 	case SCI_MARKERSETBACK:
 		if (wParam <= MARKER_MAX)
-			vs.markers[wParam].back = ColourDesired(static_cast<int>(lParam));
+			vs.markers[wParam].back = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		InvalidateStyleData();
 		RedrawSelMargin();
 		break;
 	case SCI_MARKERSETBACKSELECTED:
 		if (wParam <= MARKER_MAX)
-			vs.markers[wParam].backSelected = ColourDesired(static_cast<int>(lParam));
+			vs.markers[wParam].backSelected = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		InvalidateStyleData();
 		RedrawSelMargin();
 		break;
@@ -7118,14 +7118,14 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 
 	case SCI_SETMARGINBACKN:
 		if (ValidMargin(wParam)) {
-			vs.ms[wParam].back = ColourDesired(static_cast<int>(lParam));
+			vs.ms[wParam].back = ColourAlpha::FromRGB(static_cast<int>(lParam));
 			InvalidateStyleRedraw();
 		}
 		break;
 
 	case SCI_GETMARGINBACKN:
 		if (ValidMargin(wParam))
-			return vs.ms[wParam].back.AsInteger();
+			return vs.ms[wParam].back.OpaqueRGB();
 		else
 			return 0;
 
@@ -7187,7 +7187,7 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		break;
 
 	case SCI_GETELEMENTCOLOUR:
-		return vs.ElementColour(static_cast<int>(wParam)).value_or(ColourAlpha()).AsInteger();
+		return vs.ElementColour(static_cast<int>(wParam)).value_or(ColourAlpha()).OpaqueRGB();
 
 	case SCI_RESETELEMENTCOLOUR:
 		vs.elementColours[static_cast<int>(wParam)].reset();
@@ -7247,9 +7247,9 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		InvalidateStyleRedraw();
 		break;
 	case SCI_GETCARETLINEBACK:
-		return vs.caretLineBackground.AsInteger();
+		return vs.caretLineBackground.OpaqueRGB();
 	case SCI_SETCARETLINEBACK:
-		vs.caretLineBackground = ColourDesired(static_cast<int>(wParam));
+		vs.caretLineBackground = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 	case SCI_GETCARETLINEBACKALPHA:
@@ -7404,14 +7404,14 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		return LinesOnScreen();
 
 	case SCI_SETSELFORE:
-		vs.selColours.fore = ColourOptional(wParam, lParam);
-		vs.selAdditionalForeground = ColourDesired(static_cast<int>(lParam));
+		vs.selColours.fore = OptionalColour(wParam, lParam);
+		vs.selAdditionalForeground = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETSELBACK:
-		vs.selColours.back = ColourOptional(wParam, lParam);
-		vs.selAdditionalBackground = ColourDesired(static_cast<int>(lParam));
+		vs.selColours.back = OptionalColour(wParam, lParam);
+		vs.selAdditionalBackground = ColourAlpha::FromRGB(static_cast<int>(lParam));
 		InvalidateStyleRedraw();
 		break;
 
@@ -7433,22 +7433,22 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		break;
 
 	case SCI_SETWHITESPACEFORE:
-		vs.whitespaceColours.fore = ColourOptional(wParam, lParam);
+		vs.whitespaceColours.fore = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETWHITESPACEBACK:
-		vs.whitespaceColours.back = ColourOptional(wParam, lParam);
+		vs.whitespaceColours.back = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETCARETFORE:
-		vs.caretcolour = ColourDesired(static_cast<int>(wParam));
+		vs.caretcolour = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_GETCARETFORE:
-		return vs.caretcolour.AsInteger();
+		return vs.caretcolour.OpaqueRGB();
 
 	case SCI_SETCARETSTYLE:
 		if (wParam <= (CARETSTYLE_BLOCK | CARETSTYLE_OVERSTRIKE_BLOCK | CARETSTYLE_BLOCK_AFTER))
@@ -7497,14 +7497,14 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 
 	case SCI_INDICSETFORE:
 		if (wParam <= INDICATOR_MAX) {
-			vs.indicators[wParam].sacNormal.fore = ColourDesired(static_cast<int>(lParam));
-			vs.indicators[wParam].sacHover.fore = ColourDesired(static_cast<int>(lParam));
+			vs.indicators[wParam].sacNormal.fore = ColourAlpha::FromRGB(static_cast<int>(lParam));
+			vs.indicators[wParam].sacHover.fore = ColourAlpha::FromRGB(static_cast<int>(lParam));
 			InvalidateStyleRedraw();
 		}
 		break;
 
 	case SCI_INDICGETFORE:
-		return (wParam <= INDICATOR_MAX) ? vs.indicators[wParam].sacNormal.fore.AsInteger() : 0;
+		return (wParam <= INDICATOR_MAX) ? vs.indicators[wParam].sacNormal.fore.OpaqueRGB() : 0;
 
 	case SCI_INDICSETHOVERSTYLE:
 		if (wParam <= INDICATOR_MAX) {
@@ -7518,13 +7518,13 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 
 	case SCI_INDICSETHOVERFORE:
 		if (wParam <= INDICATOR_MAX) {
-			vs.indicators[wParam].sacHover.fore = ColourDesired(static_cast<int>(lParam));
+			vs.indicators[wParam].sacHover.fore = ColourAlpha::FromRGB(static_cast<int>(lParam));
 			InvalidateStyleRedraw();
 		}
 		break;
 
 	case SCI_INDICGETHOVERFORE:
-		return (wParam <= INDICATOR_MAX) ? vs.indicators[wParam].sacHover.fore.AsInteger() : 0;
+		return (wParam <= INDICATOR_MAX) ? vs.indicators[wParam].sacHover.fore.OpaqueRGB() : 0;
 
 	case SCI_INDICSETFLAGS:
 		if (wParam <= INDICATOR_MAX) {
@@ -7775,10 +7775,10 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		break;
 
 	case SCI_GETEDGECOLOUR:
-		return vs.theEdge.colour.AsInteger();
+		return vs.theEdge.colour.OpaqueRGB();
 
 	case SCI_SETEDGECOLOUR:
-		vs.theEdge.colour = ColourDesired(static_cast<int>(wParam));
+		vs.theEdge.colour = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
@@ -8012,30 +8012,30 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		break;
 
 	case SCI_SETFOLDMARGINCOLOUR:
-		vs.foldmarginColour = ColourOptional(wParam, lParam);
+		vs.foldmarginColour = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETFOLDMARGINHICOLOUR:
-		vs.foldmarginHighlightColour = ColourOptional(wParam, lParam);
+		vs.foldmarginHighlightColour = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETHOTSPOTACTIVEFORE:
-		vs.hotspotColours.fore = ColourOptional(wParam, lParam);
+		vs.hotspotColours.fore = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_GETHOTSPOTACTIVEFORE:
-		return vs.hotspotColours.fore.AsInteger();
+		return vs.hotspotColours.fore.value_or(ColourAlpha()).OpaqueRGB();
 
 	case SCI_SETHOTSPOTACTIVEBACK:
-		vs.hotspotColours.back = ColourOptional(wParam, lParam);
+		vs.hotspotColours.back = OptionalColour(wParam, lParam);
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_GETHOTSPOTACTIVEBACK:
-		return vs.hotspotColours.back.AsInteger();
+		return vs.hotspotColours.back.value_or(ColourAlpha()).OpaqueRGB();
 
 	case SCI_SETHOTSPOTACTIVEUNDERLINE:
 		vs.hotspotUnderline = wParam != 0;
@@ -8405,12 +8405,12 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		return virtualSpaceOptions;
 
 	case SCI_SETADDITIONALSELFORE:
-		vs.selAdditionalForeground = ColourDesired(static_cast<int>(wParam));
+		vs.selAdditionalForeground = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_SETADDITIONALSELBACK:
-		vs.selAdditionalBackground = ColourDesired(static_cast<int>(wParam));
+		vs.selAdditionalBackground = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
@@ -8423,12 +8423,12 @@ sptr_t Editor::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) {
 		return vs.selAdditionalAlpha;
 
 	case SCI_SETADDITIONALCARETFORE:
-		vs.additionalCaretColour = ColourDesired(static_cast<int>(wParam));
+		vs.additionalCaretColour = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_GETADDITIONALCARETFORE:
-		return vs.additionalCaretColour.AsInteger();
+		return vs.additionalCaretColour.OpaqueRGB();
 
 	case SCI_ROTATESELECTION:
 		sel.RotateMain();
diff --git a/src/Geometry.h b/src/Geometry.h
index ed158c081..b4d10f496 100644
--- a/src/Geometry.h
+++ b/src/Geometry.h
@@ -158,25 +158,33 @@ PRectangle PixelAlign(const PRectangle &rc, int pixelDivisions) noexcept;
 PRectangle PixelAlignOutside(const PRectangle &rc, int pixelDivisions) noexcept;
 
 /**
- * Holds an RGB colour with 8 bits for each component.
- */
+* Holds an RGBA colour with 8 bits for each component.
+*/
 constexpr const float componentMaximum = 255.0f;
-class ColourDesired {
+class ColourAlpha {
 	int co;
 public:
-	constexpr explicit ColourDesired(int co_=0) noexcept : co(co_) {
+	constexpr explicit ColourAlpha(int co_ = 0) noexcept : co(co_) {
 	}
 
-	constexpr ColourDesired(unsigned int red, unsigned int green, unsigned int blue) noexcept :
-		co(red | (green << 8) | (blue << 16)) {
+	constexpr ColourAlpha(unsigned int red, unsigned int green, unsigned int blue, unsigned int alpha=0xff) noexcept :
+		ColourAlpha(red | (green << 8) | (blue << 16) | (alpha << 24)) {
 	}
 
-	constexpr bool operator==(const ColourDesired &other) const noexcept {
-		return co == other.co;
+	constexpr ColourAlpha(ColourAlpha cd, unsigned int alpha) noexcept :
+		ColourAlpha(cd.OpaqueRGB() | (alpha << 24)) {
 	}
 
-	constexpr int AsInteger() const noexcept {
-		return co;
+	static constexpr ColourAlpha FromRGB(int co_) noexcept {
+		return ColourAlpha(co_ | (0xffu << 24));
+	}
+
+	constexpr ColourAlpha Opaque() const noexcept {
+		return ColourAlpha(co & 0xffffff);
+	}
+
+	constexpr int OpaqueRGB() const noexcept {
+		return co & 0xffffff;
 	}
 
 	// Red, green and blue values as bytes 0..255
@@ -189,8 +197,11 @@ public:
 	constexpr unsigned char GetBlue() const noexcept {
 		return (co >> 16) & 0xff;
 	}
+	constexpr unsigned char GetAlpha() const noexcept {
+		return (co >> 24) & 0xff;
+	}
 
-	// Red, green and blue values as float 0..1.0
+	// Red, green, blue, and alpha values as float 0..1.0
 	constexpr float GetRedComponent() const noexcept {
 		return GetRed() / componentMaximum;
 	}
@@ -200,40 +211,14 @@ public:
 	constexpr float GetBlueComponent() const noexcept {
 		return GetBlue() / componentMaximum;
 	}
-};
-
-/**
-* Holds an RGBA colour.
-*/
-class ColourAlpha : public ColourDesired {
-public:
-	constexpr explicit ColourAlpha(int co_ = 0) noexcept : ColourDesired(co_) {
-	}
-
-	constexpr ColourAlpha(unsigned int red, unsigned int green, unsigned int blue, unsigned int alpha=0xff) noexcept :
-		ColourDesired(red | (green << 8) | (blue << 16) | (alpha << 24)) {
-	}
-
-	constexpr ColourAlpha(ColourDesired cd, unsigned int alpha) noexcept :
-		ColourDesired(cd.AsInteger() | (alpha << 24)) {
-	}
-
-	constexpr ColourAlpha(ColourDesired cd) noexcept :
-		ColourDesired(cd.AsInteger() | (0xffu << 24)) {
-	}
-
-	constexpr ColourDesired GetColour() const noexcept {
-		return ColourDesired(AsInteger() & 0xffffff);
-	}
-
-	constexpr unsigned char GetAlpha() const noexcept {
-		return (AsInteger() >> 24) & 0xff;
-	}
-
 	constexpr float GetAlphaComponent() const noexcept {
 		return GetAlpha() / componentMaximum;
 	}
 
+	constexpr bool operator==(const ColourAlpha &other) const noexcept {
+		return co == other.co;
+	}
+
 	constexpr bool IsOpaque() const noexcept {
 		return GetAlpha() == 0xff;
 	}
@@ -271,9 +256,6 @@ public:
 	constexpr Fill(ColourAlpha colour_) noexcept : 
 		colour(colour_) {
 	}
-	constexpr Fill(ColourDesired colour_) noexcept :
-		colour(colour_) {
-	}
 };
 
 /**
diff --git a/src/Indicator.cxx b/src/Indicator.cxx
index f65b461ef..e43027837 100644
--- a/src/Indicator.cxx
+++ b/src/Indicator.cxx
@@ -28,7 +28,7 @@ using namespace Scintilla;
 void Indicator::Draw(Surface *surface, const PRectangle &rc, const PRectangle &rcLine, const PRectangle &rcCharacter, State state, int value) const {
 	StyleAndColour sacDraw = sacNormal;
 	if (Flags() & SC_INDICFLAG_VALUEFORE) {
-		sacDraw.fore = ColourDesired(value & SC_INDICVALUEMASK);
+		sacDraw.fore = ColourAlpha::FromRGB(value & SC_INDICVALUEMASK);
 	}
 	if (state == State::hover) {
 		sacDraw = sacHover;
diff --git a/src/Indicator.h b/src/Indicator.h
index 89cf1cdc5..abceec061 100644
--- a/src/Indicator.h
+++ b/src/Indicator.h
@@ -12,10 +12,10 @@ namespace Scintilla {
 
 struct StyleAndColour {
 	int style;
-	ColourDesired fore;
+	ColourAlpha fore;
 	StyleAndColour() noexcept : style(INDIC_PLAIN), fore(0, 0, 0) {
 	}
-	StyleAndColour(int style_, ColourDesired fore_ = ColourDesired(0, 0, 0)) noexcept : style(style_), fore(fore_) {
+	StyleAndColour(int style_, ColourAlpha fore_ = ColourAlpha(0, 0, 0)) noexcept : style(style_), fore(fore_) {
 	}
 	bool operator==(const StyleAndColour &other) const noexcept {
 		return (style == other.style) && (fore == other.fore);
@@ -36,7 +36,7 @@ public:
 	XYPOSITION strokeWidth = 1.0f;
 	Indicator() noexcept : under(false), fillAlpha(30), outlineAlpha(50), attributes(0) {
 	}
-	Indicator(int style_, ColourDesired fore_=ColourDesired(0,0,0), bool under_=false, int fillAlpha_=30, int outlineAlpha_=50) noexcept :
+	Indicator(int style_, ColourAlpha fore_= ColourAlpha(0,0,0), bool under_=false, int fillAlpha_=30, int outlineAlpha_=50) noexcept :
 		sacNormal(style_, fore_), sacHover(style_, fore_), under(under_), fillAlpha(fillAlpha_), outlineAlpha(outlineAlpha_), attributes(0) {
 	}
 	void Draw(Surface *surface, const PRectangle &rc, const PRectangle &rcLine, const PRectangle &rcCharacter, State drawState, int value) const;
diff --git a/src/MarginView.cxx b/src/MarginView.cxx
index 8b6f80695..2382ce1a8 100644
--- a/src/MarginView.cxx
+++ b/src/MarginView.cxx
@@ -59,7 +59,7 @@ using namespace Scintilla;
 namespace Scintilla {
 
 void DrawWrapMarker(Surface *surface, PRectangle rcPlace,
-	bool isEndMarker, ColourDesired wrapColour) {
+	bool isEndMarker, ColourAlpha wrapColour) {
 
 	const XYPOSITION extraFinalPixel = surface->Supports(SC_SUPPORTS_LINE_DRAWS_FINAL) ? 0.0f : 1.0f;
 
@@ -132,22 +132,22 @@ void MarginView::RefreshPixMaps(Surface *surfaceWindow, const ViewStyle &vsDraw)
 		const PRectangle rcPattern = PRectangle::FromInts(0, 0, patternSize, patternSize);
 
 		// Initialize default colours based on the chrome colour scheme.  Typically the highlight is white.
-		ColourDesired colourFMFill = vsDraw.selbar;
-		ColourDesired colourFMStripes = vsDraw.selbarlight;
+		ColourAlpha colourFMFill = vsDraw.selbar;
+		ColourAlpha colourFMStripes = vsDraw.selbarlight;
 
-		if (!(vsDraw.selbarlight == ColourDesired(0xff, 0xff, 0xff))) {
+		if (!(vsDraw.selbarlight == ColourAlpha(0xff, 0xff, 0xff))) {
 			// User has chosen an unusual chrome colour scheme so just use the highlight edge colour.
 			// (Typically, the highlight colour is white.)
 			colourFMFill = vsDraw.selbarlight;
 		}
 
-		if (vsDraw.foldmarginColour.isSet) {
+		if (vsDraw.foldmarginColour) {
 			// override default fold margin colour
-			colourFMFill = vsDraw.foldmarginColour;
+			colourFMFill = vsDraw.foldmarginColour.value();
 		}
-		if (vsDraw.foldmarginHighlightColour.isSet) {
+		if (vsDraw.foldmarginHighlightColour) {
 			// override default fold margin highlight colour
-			colourFMStripes = vsDraw.foldmarginHighlightColour;
+			colourFMStripes = vsDraw.foldmarginHighlightColour.value();
 		}
 
 		pixmapSelPattern->FillRectangle(rcPattern, colourFMFill);
@@ -195,7 +195,7 @@ void MarginView::PaintMargin(Surface *surface, Sci::Line topLine, PRectangle rc,
 					surface->FillRectangle(rcSelMargin,
 						invertPhase ? *pixmapSelPattern : *pixmapSelPatternOffset1);
 				} else {
-					ColourDesired colour;
+					ColourAlpha colour;
 					switch (vs.ms[margin].style) {
 					case SC_MARGIN_BACK:
 						colour = vs.styles[STYLE_DEFAULT].back;
diff --git a/src/MarginView.h b/src/MarginView.h
index 9d74ddb5e..9e52e533b 100644
--- a/src/MarginView.h
+++ b/src/MarginView.h
@@ -10,9 +10,9 @@
 
 namespace Scintilla {
 
-void DrawWrapMarker(Surface *surface, PRectangle rcPlace, bool isEndMarker, ColourDesired wrapColour);
+void DrawWrapMarker(Surface *surface, PRectangle rcPlace, bool isEndMarker, ColourAlpha wrapColour);
 
-typedef void (*DrawWrapMarkerFn)(Surface *surface, PRectangle rcPlace, bool isEndMarker, ColourDesired wrapColour);
+typedef void (*DrawWrapMarkerFn)(Surface *surface, PRectangle rcPlace, bool isEndMarker, ColourAlpha wrapColour);
 
 /**
 * MarginView draws the margins.
diff --git a/src/Platform.h b/src/Platform.h
index b77fe3243..2d14da96e 100644
--- a/src/Platform.h
+++ b/src/Platform.h
@@ -357,8 +357,8 @@ public:
  */
 namespace Platform {
 
-ColourDesired Chrome();
-ColourDesired ChromeHighlight();
+ColourAlpha Chrome();
+ColourAlpha ChromeHighlight();
 const char *DefaultFont();
 int DefaultFontSize();
 unsigned int DoubleClickTime();
diff --git a/src/ScintillaBase.cxx b/src/ScintillaBase.cxx
index 72bb5f6e0..0b9e8e41c 100644
--- a/src/ScintillaBase.cxx
+++ b/src/ScintillaBase.cxx
@@ -1008,19 +1008,19 @@ sptr_t ScintillaBase::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lPara
 		break;
 
 	case SCI_CALLTIPSETBACK:
-		ct.colourBG = ColourDesired(static_cast<int>(wParam));
+		ct.colourBG = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		vs.styles[STYLE_CALLTIP].back = ct.colourBG;
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_CALLTIPSETFORE:
-		ct.colourUnSel = ColourDesired(static_cast<int>(wParam));
+		ct.colourUnSel = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		vs.styles[STYLE_CALLTIP].fore = ct.colourUnSel;
 		InvalidateStyleRedraw();
 		break;
 
 	case SCI_CALLTIPSETFOREHLT:
-		ct.colourSel = ColourDesired(static_cast<int>(wParam));
+		ct.colourSel = ColourAlpha::FromRGB(static_cast<int>(wParam));
 		InvalidateStyleRedraw();
 		break;
 
diff --git a/src/Style.cxx b/src/Style.cxx
index 83224c736..ae5fa6aa3 100644
--- a/src/Style.cxx
+++ b/src/Style.cxx
@@ -59,13 +59,13 @@ void FontMeasurements::ClearMeasurements() noexcept {
 }
 
 Style::Style() : FontSpecification() {
-	Clear(ColourDesired(0, 0, 0), ColourDesired(0xff, 0xff, 0xff),
+	Clear(ColourAlpha(0, 0, 0), ColourAlpha(0xff, 0xff, 0xff),
 	      Platform::DefaultFontSize() * SC_FONT_SIZE_MULTIPLIER, nullptr, SC_CHARSET_DEFAULT,
 	      SC_WEIGHT_NORMAL, false, false, false, CaseForce::mixed, true, true, false);
 }
 
 Style::Style(const Style &source) noexcept : FontSpecification(), FontMeasurements() {
-	Clear(ColourDesired(0, 0, 0), ColourDesired(0xff, 0xff, 0xff),
+	Clear(ColourAlpha(0, 0, 0), ColourAlpha(0xff, 0xff, 0xff),
 	      0, nullptr, 0,
 	      SC_WEIGHT_NORMAL, false, false, false, CaseForce::mixed, true, true, false);
 	fore = source.fore;
@@ -89,7 +89,7 @@ Style::~Style() {
 Style &Style::operator=(const Style &source) noexcept {
 	if (this == &source)
 		return * this;
-	Clear(ColourDesired(0, 0, 0), ColourDesired(0xff, 0xff, 0xff),
+	Clear(ColourAlpha(0, 0, 0), ColourAlpha(0xff, 0xff, 0xff),
 	      0, nullptr, SC_CHARSET_DEFAULT,
 	      SC_WEIGHT_NORMAL, false, false, false, CaseForce::mixed, true, true, false);
 	fore = source.fore;
@@ -107,7 +107,7 @@ Style &Style::operator=(const Style &source) noexcept {
 	return *this;
 }
 
-void Style::Clear(ColourDesired fore_, ColourDesired back_, int size_,
+void Style::Clear(ColourAlpha fore_, ColourAlpha back_, int size_,
         const char *fontName_, int characterSet_,
         int weight_, bool italic_, bool eolFilled_,
         bool underline_, CaseForce caseForce_,
diff --git a/src/Style.h b/src/Style.h
index d9bf96d88..8f9b1d334 100644
--- a/src/Style.h
+++ b/src/Style.h
@@ -44,8 +44,8 @@ struct FontMeasurements {
  */
 class Style : public FontSpecification, public FontMeasurements {
 public:
-	ColourDesired fore;
-	ColourDesired back;
+	ColourAlpha fore;
+	ColourAlpha back;
 	bool eolFilled;
 	bool underline;
 	enum class CaseForce {mixed, upper, lower, camel};
@@ -62,7 +62,7 @@ public:
 	~Style();
 	Style &operator=(const Style &source) noexcept;
 	Style &operator=(Style &&) = delete;
-	void Clear(ColourDesired fore_, ColourDesired back_,
+	void Clear(ColourAlpha fore_, ColourAlpha back_,
 	           int size_,
 	           const char *fontName_, int characterSet_,
 	           int weight_, bool italic_, bool eolFilled_,
diff --git a/src/ViewStyle.cxx b/src/ViewStyle.cxx
index 5645e47fc..d4de3a6f5 100644
--- a/src/ViewStyle.cxx
+++ b/src/ViewStyle.cxx
@@ -198,9 +198,9 @@ void ViewStyle::Init(size_t stylesSize_) {
 	// There are no image markers by default, so no need for calling CalcLargestMarkerHeight()
 	largestMarkerHeight = 0;
 
-	indicators[0] = Indicator(INDIC_SQUIGGLE, ColourDesired(0, 0x7f, 0));
-	indicators[1] = Indicator(INDIC_TT, ColourDesired(0, 0, 0xff));
-	indicators[2] = Indicator(INDIC_PLAIN, ColourDesired(0xff, 0, 0));
+	indicators[0] = Indicator(INDIC_SQUIGGLE, ColourAlpha(0, 0x7f, 0));
+	indicators[1] = Indicator(INDIC_TT, ColourAlpha(0, 0, 0xff));
+	indicators[2] = Indicator(INDIC_PLAIN, ColourAlpha(0xff, 0, 0));
 
 	technology = SC_TECHNOLOGY_DEFAULT;
 	indicatorsDynamic = false;
@@ -213,40 +213,40 @@ void ViewStyle::Init(size_t stylesSize_) {
 	spaceWidth = 8;
 	tabWidth = spaceWidth * 8;
 
-	selColours.fore = ColourOptional(ColourDesired(0xff, 0, 0));
-	selColours.back = ColourOptional(ColourDesired(0xc0, 0xc0, 0xc0), true);
-	selAdditionalForeground = ColourDesired(0xff, 0, 0);
-	selAdditionalBackground = ColourDesired(0xd7, 0xd7, 0xd7);
-	selBackground2 = ColourDesired(0xb0, 0xb0, 0xb0);
+	selColours.fore.reset();
+	selColours.back = ColourAlpha(0xc0, 0xc0, 0xc0);
+	selAdditionalForeground = ColourAlpha(0xff, 0, 0);
+	selAdditionalBackground = ColourAlpha(0xd7, 0xd7, 0xd7);
+	selBackground2 = ColourAlpha(0xb0, 0xb0, 0xb0);
 	selAlpha = SC_ALPHA_NOALPHA;
 	selAdditionalAlpha = SC_ALPHA_NOALPHA;
 	selEOLFilled = false;
 
-	foldmarginColour = ColourOptional(ColourDesired(0xff, 0, 0));
-	foldmarginHighlightColour = ColourOptional(ColourDesired(0xc0, 0xc0, 0xc0));
+	foldmarginColour.reset();
+	foldmarginHighlightColour.reset();
 
-	whitespaceColours.fore = ColourOptional();
-	whitespaceColours.back = ColourOptional(ColourDesired(0xff, 0xff, 0xff));
+	whitespaceColours.fore.reset();
+	whitespaceColours.back.reset();
 	controlCharSymbol = 0;	/* Draw the control characters */
 	controlCharWidth = 0;
 	selbar = Platform::Chrome();
 	selbarlight = Platform::ChromeHighlight();
-	styles[STYLE_LINENUMBER].fore = ColourDesired(0, 0, 0);
+	styles[STYLE_LINENUMBER].fore = ColourAlpha(0, 0, 0);
 	styles[STYLE_LINENUMBER].back = Platform::Chrome();
-	caretcolour = ColourDesired(0, 0, 0);
-	additionalCaretColour = ColourDesired(0x7f, 0x7f, 0x7f);
+	caretcolour = ColourAlpha(0, 0, 0);
+	additionalCaretColour = ColourAlpha(0x7f, 0x7f, 0x7f);
 	caretLineFrame = 0;
 	showCaretLineBackground = false;
 	alwaysShowCaretLineBackground = false;
-	caretLineBackground = ColourDesired(0xff, 0xff, 0);
+	caretLineBackground = ColourAlpha(0xff, 0xff, 0);
 	caretLineAlpha = SC_ALPHA_NOALPHA;
 	caretStyle = CARETSTYLE_LINE;
 	caretWidth = 1;
 	someStylesProtected = false;
 	someStylesForceCase = false;
 
-	hotspotColours.fore = ColourOptional(ColourDesired(0, 0, 0xff));
-	hotspotColours.back = ColourOptional(ColourDesired(0xff, 0xff, 0xff));
+	hotspotColours.fore.reset();
+	hotspotColours.back.reset();
 	hotspotUnderline = true;
 	hotspotSingleLine = true;
 
@@ -279,7 +279,7 @@ void ViewStyle::Init(size_t stylesSize_) {
 	braceBadLightIndicator = 0;
 
 	edgeState = EDGE_NONE;
-	theEdge = EdgeProperties(0, ColourDesired(0xc0, 0xc0, 0xc0));
+	theEdge = EdgeProperties(0, ColourAlpha(0xc0, 0xc0, 0xc0));
 
 	marginNumberPadding = 3;
 	ctrlCharPadding = 3; // +3 For a blank on front and rounded edge each side
@@ -381,8 +381,8 @@ void ViewStyle::EnsureStyle(size_t index) {
 }
 
 void ViewStyle::ResetDefaultStyle() {
-	styles[STYLE_DEFAULT].Clear(ColourDesired(0,0,0),
-	        ColourDesired(0xff,0xff,0xff),
+	styles[STYLE_DEFAULT].Clear(ColourAlpha(0,0,0),
+	        ColourAlpha(0xff,0xff,0xff),
 	        Platform::DefaultFontSize() * SC_FONT_SIZE_MULTIPLIER, fontNames.Save(Platform::DefaultFont()),
 	        SC_CHARSET_DEFAULT,
 	        SC_WEIGHT_NORMAL, false, false, false, Style::CaseForce::mixed, true, true, false);
@@ -398,8 +398,8 @@ void ViewStyle::ClearStyles() {
 	styles[STYLE_LINENUMBER].back = Platform::Chrome();
 
 	// Set call tip fore/back to match the values previously set for call tips
-	styles[STYLE_CALLTIP].back = ColourDesired(0xff, 0xff, 0xff);
-	styles[STYLE_CALLTIP].fore = ColourDesired(0x80, 0x80, 0x80);
+	styles[STYLE_CALLTIP].back = ColourAlpha(0xff, 0xff, 0xff);
+	styles[STYLE_CALLTIP].fore = ColourAlpha(0x80, 0x80, 0x80);
 }
 
 void ViewStyle::SetStyleFontName(int styleIndex, const char *name) {
@@ -464,29 +464,29 @@ bool ViewStyle::IsLineFrameOpaque(bool caretActive, bool lineContainsCaret) cons
 // display itself (as long as it's not an SC_MARK_EMPTY marker).  These are checked in order
 // with the earlier taking precedence.  When multiple markers cause background override,
 // the colour for the highest numbered one is used.
-ColourOptional ViewStyle::Background(int marksOfLine, bool caretActive, bool lineContainsCaret) const noexcept {
-	ColourOptional background;
+std::optional<ColourAlpha> ViewStyle::Background(int marksOfLine, bool caretActive, bool lineContainsCaret) const {
+	std::optional<ColourAlpha> background;
 	if (!caretLineFrame && (caretActive || alwaysShowCaretLineBackground) && showCaretLineBackground &&
 		(caretLineAlpha == SC_ALPHA_NOALPHA) && lineContainsCaret) {
-		background = ColourOptional(caretLineBackground, true);
+		background = caretLineBackground;
 	}
-	if (!background.isSet && marksOfLine) {
+	if (!background && marksOfLine) {
 		int marks = marksOfLine;
 		for (int markBit = 0; (markBit < 32) && marks; markBit++) {
 			if ((marks & 1) && (markers[markBit].markType == SC_MARK_BACKGROUND) &&
 				(markers[markBit].alpha == SC_ALPHA_NOALPHA)) {
-				background = ColourOptional(markers[markBit].back, true);
+				background = markers[markBit].back;
 			}
 			marks >>= 1;
 		}
 	}
-	if (!background.isSet && maskInLine) {
+	if (!background && maskInLine) {
 		int marksMasked = marksOfLine & maskInLine;
 		if (marksMasked) {
 			for (int markBit = 0; (markBit < 32) && marksMasked; markBit++) {
 				if ((marksMasked & 1) &&
 					(markers[markBit].alpha == SC_ALPHA_NOALPHA)) {
-					background = ColourOptional(markers[markBit].back, true);
+					background = markers[markBit].back;
 				}
 				marksMasked >>= 1;
 			}
@@ -496,12 +496,12 @@ ColourOptional ViewStyle::Background(int marksOfLine, bool caretActive, bool lin
 }
 
 bool ViewStyle::SelectionBackgroundDrawn() const noexcept {
-	return selColours.back.isSet &&
+	return selColours.back &&
 		((selAlpha == SC_ALPHA_NOALPHA) || (selAdditionalAlpha == SC_ALPHA_NOALPHA));
 }
 
 bool ViewStyle::WhitespaceBackgroundDrawn() const noexcept {
-	return (viewWhitespace != WhiteSpace::invisible) && (whitespaceColours.back.isSet);
+	return (viewWhitespace != WhiteSpace::invisible) && (whitespaceColours.back);
 }
 
 bool ViewStyle::WhiteSpaceVisible(bool inIndent) const noexcept {
@@ -510,11 +510,8 @@ bool ViewStyle::WhiteSpaceVisible(bool inIndent) const noexcept {
 		viewWhitespace == WhiteSpace::visibleAlways;
 }
 
-ColourDesired ViewStyle::WrapColour() const noexcept {
-	if (whitespaceColours.fore.isSet)
-		return whitespaceColours.fore;
-	else
-		return styles[STYLE_DEFAULT].fore;
+ColourAlpha ViewStyle::WrapColour() const noexcept {
+	return whitespaceColours.fore.value_or(styles[STYLE_DEFAULT].fore);
 }
 
 // Insert new edge in sorted order.
diff --git a/src/ViewStyle.h b/src/ViewStyle.h
index 946bd6c60..c9fe6bc98 100644
--- a/src/ViewStyle.h
+++ b/src/ViewStyle.h
@@ -15,7 +15,7 @@ namespace Scintilla {
 class MarginStyle {
 public:
 	int style;
-	ColourDesired back;
+	ColourAlpha back;
 	int width;
 	int mask;
 	bool sensitive;
@@ -50,28 +50,27 @@ typedef std::map<FontSpecification, std::unique_ptr<FontRealised>> FontMap;
 
 enum class WrapMode { none, word, character, whitespace };
 
-class ColourOptional : public ColourDesired {
-public:
-	bool isSet;
-	ColourOptional(ColourDesired colour_=ColourDesired(0,0,0), bool isSet_=false) noexcept : ColourDesired(colour_), isSet(isSet_) {
-	}
-	ColourOptional(uptr_t wParam, sptr_t lParam) noexcept : ColourDesired(static_cast<int>(lParam)), isSet(wParam != 0) {
+inline std::optional<ColourAlpha> OptionalColour(uptr_t wParam, sptr_t lParam) {
+	if (wParam) {
+		return ColourAlpha::FromRGB(static_cast<int>(lParam));
+	} else {
+		return {};
 	}
-};
+}
 
 struct ForeBackColours {
-	ColourOptional fore;
-	ColourOptional back;
+	std::optional<ColourAlpha> fore;
+	std::optional<ColourAlpha> back;
 };
 
 struct EdgeProperties {
-	int column;
-	ColourDesired colour;
-	EdgeProperties(int column_ = 0, ColourDesired colour_ = ColourDesired(0)) noexcept :
+	int column = 0;
+	ColourAlpha colour;
+	EdgeProperties(int column_ = 0, ColourAlpha colour_ = ColourAlpha::FromRGB(0)) noexcept :
 		column(column_), colour(colour_) {
 	}
 	EdgeProperties(uptr_t wParam, sptr_t lParam) noexcept :
-		column(static_cast<int>(wParam)), colour(static_cast<int>(lParam)) {
+		column(static_cast<int>(wParam)), colour(ColourAlpha::FromRGB(static_cast<int>(lParam))) {
 	}
 };
 
@@ -97,19 +96,19 @@ public:
 	XYPOSITION spaceWidth;
 	XYPOSITION tabWidth;
 	ForeBackColours selColours;
-	ColourDesired selAdditionalForeground;
-	ColourDesired selAdditionalBackground;
-	ColourDesired selBackground2;
+	ColourAlpha selAdditionalForeground;
+	ColourAlpha selAdditionalBackground;
+	ColourAlpha selBackground2;
 	int selAlpha;
 	int selAdditionalAlpha;
 	bool selEOLFilled;
 	ForeBackColours whitespaceColours;
 	int controlCharSymbol;
 	XYPOSITION controlCharWidth;
-	ColourDesired selbar;
-	ColourDesired selbarlight;
-	ColourOptional foldmarginColour;
-	ColourOptional foldmarginHighlightColour;
+	ColourAlpha selbar;
+	ColourAlpha selbarlight;
+	std::optional<ColourAlpha> foldmarginColour;
+	std::optional<ColourAlpha> foldmarginHighlightColour;
 	ForeBackColours hotspotColours;
 	bool hotspotUnderline;
 	bool hotspotSingleLine;
@@ -128,12 +127,12 @@ public:
 	int whitespaceSize;
 	IndentView viewIndentationGuides;
 	bool viewEOL;
-	ColourDesired caretcolour;
-	ColourDesired additionalCaretColour;
+	ColourAlpha caretcolour;
+	ColourAlpha additionalCaretColour;
 	int caretLineFrame;
 	bool showCaretLineBackground;
 	bool alwaysShowCaretLineBackground;
-	ColourDesired caretLineBackground;
+	ColourAlpha caretLineBackground;
 	int caretLineAlpha;
 	int caretStyle;
 	int caretWidth;
@@ -194,10 +193,10 @@ public:
 	void CalcLargestMarkerHeight() noexcept;
 	int GetFrameWidth() const noexcept;
 	bool IsLineFrameOpaque(bool caretActive, bool lineContainsCaret) const noexcept;
-	ColourOptional Background(int marksOfLine, bool caretActive, bool lineContainsCaret) const noexcept;
+	std::optional<ColourAlpha> Background(int marksOfLine, bool caretActive, bool lineContainsCaret) const;
 	bool SelectionBackgroundDrawn() const noexcept;
 	bool WhitespaceBackgroundDrawn() const noexcept;
-	ColourDesired WrapColour() const noexcept;
+	ColourAlpha WrapColour() const noexcept;
 
 	void AddMultiEdge(uptr_t wParam, sptr_t lParam);