Add support for red text and highlighted text in markdown

lib/sequence-diagram-web.js

@@ -60,8 +60,58 @@
 			// No-op
 		}
 
-		addDefs() {
-			// No-op
+		addDefs(builder, textBuilder) {
+			// Thanks, https://stackoverflow.com/a/12263962/1180785
+			// https://bugs.chromium.org/p/chromium/issues/detail?id=603157
+			// https://bugzilla.mozilla.org/show_bug.cgi?id=917766
+			textBuilder('highlight', () => this.svg.el('filter')
+				.add(
+					// Morph makes characters consistent
+					this.svg.el('feMorphology').attrs({
+						'in': 'SourceAlpha',
+						'operator': 'dilate',
+						'radius': '4',
+					}),
+					// Blur+thresh makes edges smooth
+					this.svg.el('feGaussianBlur').attrs({
+						'edgeMode': 'none',
+						'stdDeviation': '3, 1.5',
+					}),
+					this.svg.el('feComponentTransfer').add(
+						this.svg.el('feFuncA').attrs({
+							'intercept': -70,
+							'slope': 100,
+							'type': 'linear',
+						})
+					),
+					// Add colour
+					this.svg.el('feComponentTransfer').add(
+						this.svg.el('feFuncR').attrs({
+							'intercept': 1,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncG').attrs({
+							'intercept': 0.9375,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncB').attrs({
+							'intercept': 0.09375,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncA').attrs({
+							'slope': 0.7,
+							'type': 'linear',
+						})
+					),
+					// Draw text on top
+					this.svg.el('feMerge').add(
+						this.svg.el('feMergeNode'),
+						this.svg.el('feMergeNode').attr('in', 'SourceGraphic')
+					)
+				));
 		}
 
 		getTitleAttrs() {
@@ -3837,7 +3887,7 @@
 			start: /"/y,
 		},
 		{baseToken: {v: '...'}, start: /\.\.\./y},
-		{end: /(?=[ \t\r\n:+~\-*!<>,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<>,])/y},
+		{end: /(?=[ \t\r\n:+~\-*!<,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<,])/y},
 		{
 			end: /(?=[^~\-<>x])|[-~]x|[<>](?=x)|$/y,
 			includeEnd: true,
@@ -4109,28 +4159,36 @@
 	const STYLES = [
 		{
 			attrs: {'font-style': 'italic'},
-			begin: /[\s_~`]\*(?=\S)/g,
-			end: /\S\*(?=[\s_~`])/g,
+			begin: {matcher: /[\s_~`>]\*(?=\S)/g, skip: 1},
+			end: {matcher: /\S\*(?=[\s_~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-style': 'italic'},
-			begin: /[\s*~`]_(?=\S)/g,
-			end: /\S_(?=[\s*~`])/g,
+			begin: {matcher: /[\s*~`>]_(?=\S)/g, skip: 1},
+			end: {matcher: /\S_(?=[\s*~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-weight': 'bolder'},
-			begin: /[\s_~`]\*\*(?=\S)/g,
-			end: /\S\*\*(?=[\s_~`])/g,
+			begin: {matcher: /[\s_~`>]\*\*(?=\S)/g, skip: 1},
+			end: {matcher: /\S\*\*(?=[\s_~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-weight': 'bolder'},
-			begin: /[\s*~`]__(?=\S)/g,
-			end: /\S__(?=[\s*~`])/g,
+			begin: {matcher: /[\s*~`>]__(?=\S)/g, skip: 1},
+			end: {matcher: /\S__(?=[\s*~`<])/g, skip: 1},
 		}, {
 			attrs: {'text-decoration': 'line-through'},
-			begin: /[\s_*`]~(?=\S)/g,
-			end: /\S~(?=[\s_*`])/g,
+			begin: {matcher: /[\s_*`>]~(?=\S)/g, skip: 1},
+			end: {matcher: /\S~(?=[\s_*`<])/g, skip: 1},
 		}, {
 			attrs: {'font-family': 'Courier New,Liberation Mono,monospace'},
-			begin: /[\s_*~.]`(?=\S)/g,
-			end: /\S`(?=[\s_*~.])/g,
+			begin: {matcher: /[\s_*~.>]`(?=\S)/g, skip: 1},
+			end: {matcher: /\S`(?=[\s_*~.<])/g, skip: 1},
+		}, {
+			attrs: {'fill': '#DD0000'},
+			begin: {matcher: /<red>/g, skip: 0},
+			end: {matcher: /<\/red>/g, skip: 0},
+		}, {
+			attrs: {'filter': 'highlight'},
+			begin: {matcher: /<highlight>/g, skip: 0},
+			end: {matcher: /<\/highlight>/g, skip: 0},
 		},
 	];
 
@@ -4142,19 +4200,20 @@
 
 		STYLES.forEach(({begin, end}, ind) => {
 			const search = active[ind] ? end : begin;
-			search.lastIndex = p;
-			const m = search.exec(virtLine);
-			if(m && (
-				m.index < bestStart ||
-				(m.index === bestStart && search.lastIndex > bestEnd)
-			)) {
+			search.matcher.lastIndex = p + 1 - search.skip;
+			const m = search.matcher.exec(virtLine);
+			const beginInd = m ? (m.index + search.skip) : Number.POSITIVE_INFINITY;
+			if(
+				beginInd < bestStart ||
+				(beginInd === bestStart && search.matcher.lastIndex > bestEnd)
+			) {
 				styleIndex = ind;
-				bestStart = m.index;
-				bestEnd = search.lastIndex;
+				bestStart = beginInd;
+				bestEnd = search.matcher.lastIndex;
 			}
 		});
 
-		return {end: bestEnd - 1, start: bestStart, styleIndex};
+		return {end: bestEnd - 1, start: bestStart - 1, styleIndex};
 	}
 
 	function combineAttrs(activeCount, active) {
@@ -6776,7 +6835,9 @@
 		}
 
 		detach() {
-			this.element.parentNode.removeChild(this.element);
+			if(this.element.parentNode) {
+				this.element.parentNode.removeChild(this.element);
+			}
 			return this;
 		}
 	}
@@ -6830,11 +6891,14 @@
 			throw new Error('Invalid formatted text line: ' + formattedLine);
 		}
 		formattedLine.forEach(({text, attrs}) => {
+			let element = text;
 			if(attrs) {
-				node.add(svg.el('tspan').attrs(attrs).add(text));
-			} else {
-				node.add(text);
+				element = svg.el('tspan').attrs(attrs).add(text);
+				if(attrs.filter) {
+					element.attr('filter', svg.getTextFilter(attrs.filter));
+				}
 			}
+			node.add(element);
 		});
 	}
 
@@ -7282,12 +7346,40 @@
 			this.dom = domWrapper;
 			this.body = this.el('svg').attr('xmlns', NS).attr('version', '1.1');
 			const fn = (textSizerFactory || defaultTextSizerFactory);
+			this.textFilters = new Map();
 			this.textSizer = new TextSizerWrapper(fn(this));
 
 			this.txt = this.txt.bind(this);
 			this.el = this.el.bind(this);
 		}
 
+		resetTextFilters() {
+			this.textFilters.clear();
+		}
+
+		registerTextFilter(name, id) {
+			this.textFilters.set(name, {id, used: false});
+		}
+
+		getTextFilter(name) {
+			const filter = this.textFilters.get(name);
+			if(!filter) {
+				return 'none';
+			}
+			filter.used = true;
+			return 'url(#' + filter.id + ')';
+		}
+
+		getUsedTextFilterNames() {
+			const used = [];
+			for(const [name, filter] of this.textFilters) {
+				if(filter.used) {
+					used.push(name);
+				}
+			}
+			return used;
+		}
+
 		linearGradient(attrs, stops) {
 			return this.el('linearGradient')
 				.attrs(attrs)
@@ -7508,6 +7600,7 @@
 			this.components = components || getComponents();
 			this.svg = new SVG(new DOMWrapper(document), textSizerFactory);
 			this.knownThemeDefs = new Set();
+			this.knownTextFilterDefs = new Map();
 			this.knownDefs = new Set();
 			this.highlights = new Map();
 			this.collapsed = new Set();
@@ -7524,6 +7617,7 @@
 				this.prepareMeasurementsStage.bind(this);
 			this.renderStage = this.renderStage.bind(this);
 			this.addThemeDef = this.addThemeDef.bind(this);
+			this.addThemeTextDef = this.addThemeTextDef.bind(this);
 			this.addDef = this.addDef.bind(this);
 		}
 
@@ -7582,6 +7676,15 @@
 			return namespacedName;
 		}
 
+		addThemeTextDef(name, generator) {
+			const namespacedName = this.namespace + name;
+			if(!this.knownTextFilterDefs.has(name)) {
+				const def = generator().attr('id', namespacedName);
+				this.knownTextFilterDefs.set(name, def);
+			}
+			this.svg.registerTextFilter(name, namespacedName);
+		}
+
 		addDef(name, generator) {
 			let nm = name;
 			let gen = generator;
@@ -7963,6 +8066,7 @@
 		_reset(theme) {
 			if(theme) {
 				this.knownThemeDefs.clear();
+				this.knownTextFilterDefs.clear();
 				this.themeDefs.empty();
 			}
 
@@ -8060,7 +8164,11 @@
 			this._reset(themeChanged);
 
 			this.metaCode.nodeValue = sequence.meta.code;
-			this.theme.addDefs(this.addThemeDef);
+			this.svg.resetTextFilters();
+			this.theme.addDefs(this.addThemeDef, this.addThemeTextDef);
+			for(const def of this.knownTextFilterDefs.values()) {
+				def.detach();
+			}
 
 			this.title.set({
 				attrs: Object.assign({
@@ -8094,6 +8202,10 @@
 			sequence.stages.forEach(this.renderStage);
 			const bottomY = this.checkAgentRange(['[', ']'], this.currentY);
 
+			this.svg.getUsedTextFilterNames().forEach((name) => {
+				this.themeDefs.add(this.knownTextFilterDefs.get(name));
+			});
+
 			const stagesHeight = Math.max(bottomY - this.theme.actionMargin, 0);
 			this.updateBounds(stagesHeight);
 
@@ -8962,7 +9074,7 @@
 			this.random.reset();
 		}
 
-		addDefs(builder) {
+		addDefs(builder, textBuilder) {
 			builder('sketch_font', () => {
 				const style = this.svg.el('style', null);
 				// Font must be embedded for exporting as SVG / PNG
@@ -8974,6 +9086,8 @@
 				);
 				return style;
 			});
+
+			super.addDefs(builder, textBuilder);
 		}
 
 		vary(range, centre = 0) {

lib/sequence-diagram.js

@@ -60,8 +60,58 @@
 			// No-op
 		}
 
-		addDefs() {
-			// No-op
+		addDefs(builder, textBuilder) {
+			// Thanks, https://stackoverflow.com/a/12263962/1180785
+			// https://bugs.chromium.org/p/chromium/issues/detail?id=603157
+			// https://bugzilla.mozilla.org/show_bug.cgi?id=917766
+			textBuilder('highlight', () => this.svg.el('filter')
+				.add(
+					// Morph makes characters consistent
+					this.svg.el('feMorphology').attrs({
+						'in': 'SourceAlpha',
+						'operator': 'dilate',
+						'radius': '4',
+					}),
+					// Blur+thresh makes edges smooth
+					this.svg.el('feGaussianBlur').attrs({
+						'edgeMode': 'none',
+						'stdDeviation': '3, 1.5',
+					}),
+					this.svg.el('feComponentTransfer').add(
+						this.svg.el('feFuncA').attrs({
+							'intercept': -70,
+							'slope': 100,
+							'type': 'linear',
+						})
+					),
+					// Add colour
+					this.svg.el('feComponentTransfer').add(
+						this.svg.el('feFuncR').attrs({
+							'intercept': 1,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncG').attrs({
+							'intercept': 0.9375,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncB').attrs({
+							'intercept': 0.09375,
+							'slope': 0,
+							'type': 'linear',
+						}),
+						this.svg.el('feFuncA').attrs({
+							'slope': 0.7,
+							'type': 'linear',
+						})
+					),
+					// Draw text on top
+					this.svg.el('feMerge').add(
+						this.svg.el('feMergeNode'),
+						this.svg.el('feMergeNode').attr('in', 'SourceGraphic')
+					)
+				));
 		}
 
 		getTitleAttrs() {
@@ -3837,7 +3887,7 @@
 			start: /"/y,
 		},
 		{baseToken: {v: '...'}, start: /\.\.\./y},
-		{end: /(?=[ \t\r\n:+~\-*!<>,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<>,])/y},
+		{end: /(?=[ \t\r\n:+~\-*!<,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<,])/y},
 		{
 			end: /(?=[^~\-<>x])|[-~]x|[<>](?=x)|$/y,
 			includeEnd: true,
@@ -4109,28 +4159,36 @@
 	const STYLES = [
 		{
 			attrs: {'font-style': 'italic'},
-			begin: /[\s_~`]\*(?=\S)/g,
-			end: /\S\*(?=[\s_~`])/g,
+			begin: {matcher: /[\s_~`>]\*(?=\S)/g, skip: 1},
+			end: {matcher: /\S\*(?=[\s_~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-style': 'italic'},
-			begin: /[\s*~`]_(?=\S)/g,
-			end: /\S_(?=[\s*~`])/g,
+			begin: {matcher: /[\s*~`>]_(?=\S)/g, skip: 1},
+			end: {matcher: /\S_(?=[\s*~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-weight': 'bolder'},
-			begin: /[\s_~`]\*\*(?=\S)/g,
-			end: /\S\*\*(?=[\s_~`])/g,
+			begin: {matcher: /[\s_~`>]\*\*(?=\S)/g, skip: 1},
+			end: {matcher: /\S\*\*(?=[\s_~`<])/g, skip: 1},
 		}, {
 			attrs: {'font-weight': 'bolder'},
-			begin: /[\s*~`]__(?=\S)/g,
-			end: /\S__(?=[\s*~`])/g,
+			begin: {matcher: /[\s*~`>]__(?=\S)/g, skip: 1},
+			end: {matcher: /\S__(?=[\s*~`<])/g, skip: 1},
 		}, {
 			attrs: {'text-decoration': 'line-through'},
-			begin: /[\s_*`]~(?=\S)/g,
-			end: /\S~(?=[\s_*`])/g,
+			begin: {matcher: /[\s_*`>]~(?=\S)/g, skip: 1},
+			end: {matcher: /\S~(?=[\s_*`<])/g, skip: 1},
 		}, {
 			attrs: {'font-family': 'Courier New,Liberation Mono,monospace'},
-			begin: /[\s_*~.]`(?=\S)/g,
-			end: /\S`(?=[\s_*~.])/g,
+			begin: {matcher: /[\s_*~.>]`(?=\S)/g, skip: 1},
+			end: {matcher: /\S`(?=[\s_*~.<])/g, skip: 1},
+		}, {
+			attrs: {'fill': '#DD0000'},
+			begin: {matcher: /<red>/g, skip: 0},
+			end: {matcher: /<\/red>/g, skip: 0},
+		}, {
+			attrs: {'filter': 'highlight'},
+			begin: {matcher: /<highlight>/g, skip: 0},
+			end: {matcher: /<\/highlight>/g, skip: 0},
 		},
 	];
 
@@ -4142,19 +4200,20 @@
 
 		STYLES.forEach(({begin, end}, ind) => {
 			const search = active[ind] ? end : begin;
-			search.lastIndex = p;
-			const m = search.exec(virtLine);
-			if(m && (
-				m.index < bestStart ||
-				(m.index === bestStart && search.lastIndex > bestEnd)
-			)) {
+			search.matcher.lastIndex = p + 1 - search.skip;
+			const m = search.matcher.exec(virtLine);
+			const beginInd = m ? (m.index + search.skip) : Number.POSITIVE_INFINITY;
+			if(
+				beginInd < bestStart ||
+				(beginInd === bestStart && search.matcher.lastIndex > bestEnd)
+			) {
 				styleIndex = ind;
-				bestStart = m.index;
-				bestEnd = search.lastIndex;
+				bestStart = beginInd;
+				bestEnd = search.matcher.lastIndex;
 			}
 		});
 
-		return {end: bestEnd - 1, start: bestStart, styleIndex};
+		return {end: bestEnd - 1, start: bestStart - 1, styleIndex};
 	}
 
 	function combineAttrs(activeCount, active) {
@@ -6776,7 +6835,9 @@
 		}
 
 		detach() {
-			this.element.parentNode.removeChild(this.element);
+			if(this.element.parentNode) {
+				this.element.parentNode.removeChild(this.element);
+			}
 			return this;
 		}
 	}
@@ -6830,11 +6891,14 @@
 			throw new Error('Invalid formatted text line: ' + formattedLine);
 		}
 		formattedLine.forEach(({text, attrs}) => {
+			let element = text;
 			if(attrs) {
-				node.add(svg.el('tspan').attrs(attrs).add(text));
-			} else {
-				node.add(text);
+				element = svg.el('tspan').attrs(attrs).add(text);
+				if(attrs.filter) {
+					element.attr('filter', svg.getTextFilter(attrs.filter));
+				}
 			}
+			node.add(element);
 		});
 	}
 
@@ -7282,12 +7346,40 @@
 			this.dom = domWrapper;
 			this.body = this.el('svg').attr('xmlns', NS).attr('version', '1.1');
 			const fn = (textSizerFactory || defaultTextSizerFactory);
+			this.textFilters = new Map();
 			this.textSizer = new TextSizerWrapper(fn(this));
 
 			this.txt = this.txt.bind(this);
 			this.el = this.el.bind(this);
 		}
 
+		resetTextFilters() {
+			this.textFilters.clear();
+		}
+
+		registerTextFilter(name, id) {
+			this.textFilters.set(name, {id, used: false});
+		}
+
+		getTextFilter(name) {
+			const filter = this.textFilters.get(name);
+			if(!filter) {
+				return 'none';
+			}
+			filter.used = true;
+			return 'url(#' + filter.id + ')';
+		}
+
+		getUsedTextFilterNames() {
+			const used = [];
+			for(const [name, filter] of this.textFilters) {
+				if(filter.used) {
+					used.push(name);
+				}
+			}
+			return used;
+		}
+
 		linearGradient(attrs, stops) {
 			return this.el('linearGradient')
 				.attrs(attrs)
@@ -7508,6 +7600,7 @@
 			this.components = components || getComponents();
 			this.svg = new SVG(new DOMWrapper(document), textSizerFactory);
 			this.knownThemeDefs = new Set();
+			this.knownTextFilterDefs = new Map();
 			this.knownDefs = new Set();
 			this.highlights = new Map();
 			this.collapsed = new Set();
@@ -7524,6 +7617,7 @@
 				this.prepareMeasurementsStage.bind(this);
 			this.renderStage = this.renderStage.bind(this);
 			this.addThemeDef = this.addThemeDef.bind(this);
+			this.addThemeTextDef = this.addThemeTextDef.bind(this);
 			this.addDef = this.addDef.bind(this);
 		}
 
@@ -7582,6 +7676,15 @@
 			return namespacedName;
 		}
 
+		addThemeTextDef(name, generator) {
+			const namespacedName = this.namespace + name;
+			if(!this.knownTextFilterDefs.has(name)) {
+				const def = generator().attr('id', namespacedName);
+				this.knownTextFilterDefs.set(name, def);
+			}
+			this.svg.registerTextFilter(name, namespacedName);
+		}
+
 		addDef(name, generator) {
 			let nm = name;
 			let gen = generator;
@@ -7963,6 +8066,7 @@
 		_reset(theme) {
 			if(theme) {
 				this.knownThemeDefs.clear();
+				this.knownTextFilterDefs.clear();
 				this.themeDefs.empty();
 			}
 
@@ -8060,7 +8164,11 @@
 			this._reset(themeChanged);
 
 			this.metaCode.nodeValue = sequence.meta.code;
-			this.theme.addDefs(this.addThemeDef);
+			this.svg.resetTextFilters();
+			this.theme.addDefs(this.addThemeDef, this.addThemeTextDef);
+			for(const def of this.knownTextFilterDefs.values()) {
+				def.detach();
+			}
 
 			this.title.set({
 				attrs: Object.assign({
@@ -8094,6 +8202,10 @@
 			sequence.stages.forEach(this.renderStage);
 			const bottomY = this.checkAgentRange(['[', ']'], this.currentY);
 
+			this.svg.getUsedTextFilterNames().forEach((name) => {
+				this.themeDefs.add(this.knownTextFilterDefs.get(name));
+			});
+
 			const stagesHeight = Math.max(bottomY - this.theme.actionMargin, 0);
 			this.updateBounds(stagesHeight);
 
@@ -8962,7 +9074,7 @@
 			this.random.reset();
 		}
 
-		addDefs(builder) {
+		addDefs(builder, textBuilder) {
 			builder('sketch_font', () => {
 				const style = this.svg.el('style', null);
 				// Font must be embedded for exporting as SVG / PNG
@@ -8974,6 +9086,8 @@
 				);
 				return style;
 			});
+
+			super.addDefs(builder, textBuilder);
 		}
 
 		vary(range, centre = 0) {

scripts/core/DOMWrapper.mjs

@@ -164,7 +164,9 @@ class WrappedElement {
 	}
 
 	detach() {
-		this.element.parentNode.removeChild(this.element);
+		if(this.element.parentNode) {
+			this.element.parentNode.removeChild(this.element);
+		}
 		return this;
 	}
 }

scripts/sequence/SequenceDiagram_spec.mjs

@@ -171,4 +171,11 @@ describe('SequenceDiagram', () => {
 
 		expect(content).toContain('<g class="region collapsed"');
 	});
+
+	it('includes text filters if used', () => {
+		const diagram = makeDiagram('title <highlight>foo</highlight>');
+		const content = getSimplifiedContent(diagram);
+
+		expect(content).toContain('<filter id="highlight"');
+	});
 });

scripts/sequence/parser/MarkdownParser.mjs

@@ -1,28 +1,36 @@
 const STYLES = [
 	{
 		attrs: {'font-style': 'italic'},
-		begin: /[\s_~`]\*(?=\S)/g,
-		end: /\S\*(?=[\s_~`])/g,
+		begin: {matcher: /[\s_~`>]\*(?=\S)/g, skip: 1},
+		end: {matcher: /\S\*(?=[\s_~`<])/g, skip: 1},
 	}, {
 		attrs: {'font-style': 'italic'},
-		begin: /[\s*~`]_(?=\S)/g,
-		end: /\S_(?=[\s*~`])/g,
+		begin: {matcher: /[\s*~`>]_(?=\S)/g, skip: 1},
+		end: {matcher: /\S_(?=[\s*~`<])/g, skip: 1},
 	}, {
 		attrs: {'font-weight': 'bolder'},
-		begin: /[\s_~`]\*\*(?=\S)/g,
-		end: /\S\*\*(?=[\s_~`])/g,
+		begin: {matcher: /[\s_~`>]\*\*(?=\S)/g, skip: 1},
+		end: {matcher: /\S\*\*(?=[\s_~`<])/g, skip: 1},
 	}, {
 		attrs: {'font-weight': 'bolder'},
-		begin: /[\s*~`]__(?=\S)/g,
-		end: /\S__(?=[\s*~`])/g,
+		begin: {matcher: /[\s*~`>]__(?=\S)/g, skip: 1},
+		end: {matcher: /\S__(?=[\s*~`<])/g, skip: 1},
 	}, {
 		attrs: {'text-decoration': 'line-through'},
-		begin: /[\s_*`]~(?=\S)/g,
-		end: /\S~(?=[\s_*`])/g,
+		begin: {matcher: /[\s_*`>]~(?=\S)/g, skip: 1},
+		end: {matcher: /\S~(?=[\s_*`<])/g, skip: 1},
 	}, {
 		attrs: {'font-family': 'Courier New,Liberation Mono,monospace'},
-		begin: /[\s_*~.]`(?=\S)/g,
-		end: /\S`(?=[\s_*~.])/g,
+		begin: {matcher: /[\s_*~.>]`(?=\S)/g, skip: 1},
+		end: {matcher: /\S`(?=[\s_*~.<])/g, skip: 1},
+	}, {
+		attrs: {'fill': '#DD0000'},
+		begin: {matcher: /<red>/g, skip: 0},
+		end: {matcher: /<\/red>/g, skip: 0},
+	}, {
+		attrs: {'filter': 'highlight'},
+		begin: {matcher: /<highlight>/g, skip: 0},
+		end: {matcher: /<\/highlight>/g, skip: 0},
 	},
 ];
 
@@ -34,19 +42,20 @@ function findNext(line, p, active) {
 
 	STYLES.forEach(({begin, end}, ind) => {
 		const search = active[ind] ? end : begin;
-		search.lastIndex = p;
-		const m = search.exec(virtLine);
-		if(m && (
-			m.index < bestStart ||
-			(m.index === bestStart && search.lastIndex > bestEnd)
-		)) {
+		search.matcher.lastIndex = p + 1 - search.skip;
+		const m = search.matcher.exec(virtLine);
+		const beginInd = m ? (m.index + search.skip) : Number.POSITIVE_INFINITY;
+		if(
+			beginInd < bestStart ||
+			(beginInd === bestStart && search.matcher.lastIndex > bestEnd)
+		) {
 			styleIndex = ind;
-			bestStart = m.index;
-			bestEnd = search.lastIndex;
+			bestStart = beginInd;
+			bestEnd = search.matcher.lastIndex;
 		}
 	});
 
-	return {end: bestEnd - 1, start: bestStart, styleIndex};
+	return {end: bestEnd - 1, start: bestStart - 1, styleIndex};
 }
 
 function combineAttrs(activeCount, active) {

scripts/sequence/parser/MarkdownParser_spec.mjs

@@ -117,6 +117,26 @@ describe('Markdown Parser', () => {
 		]]);
 	});
 
+	it('recognises red styling', () => {
+		const formatted = parser('a <red>b</red> c');
+
+		expect(formatted).toEqual([[
+			{attrs: null, text: 'a '},
+			{attrs: {'fill': '#DD0000'}, text: 'b'},
+			{attrs: null, text: ' c'},
+		]]);
+	});
+
+	it('recognises highlight styling', () => {
+		const formatted = parser('a <highlight>b</highlight> c');
+
+		expect(formatted).toEqual([[
+			{attrs: null, text: 'a '},
+			{attrs: {'filter': 'highlight'}, text: 'b'},
+			{attrs: null, text: ' c'},
+		]]);
+	});
+
 	it('allows dots around monospace styling', () => {
 		const formatted = parser('a.`b`.c');
 
@@ -140,6 +160,18 @@ describe('Markdown Parser', () => {
 		]]);
 	});
 
+	it('recognises heavily combined styling', () => {
+		const formatted = parser('**_`abc`_**');
+
+		expect(formatted).toEqual([[
+			{attrs: {
+				'font-family': MONO_FONT,
+				'font-style': 'italic',
+				'font-weight': 'bolder',
+			}, text: 'abc'},
+		]]);
+	});
+
 	it('allows complex interactions between styles', () => {
 		const formatted = parser('_a **b_ ~c~**');
 

scripts/sequence/parser/Tokeniser.mjs

@@ -22,7 +22,7 @@ const TOKENS = [
 		start: /"/y,
 	},
 	{baseToken: {v: '...'}, start: /\.\.\./y},
-	{end: /(?=[ \t\r\n:+~\-*!<>,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<>,])/y},
+	{end: /(?=[ \t\r\n:+~\-*!<,])|$/y, start: /(?=[^ \t\r\n:+~\-*!<,])/y},
 	{
 		end: /(?=[^~\-<>x])|[-~]x|[<>](?=x)|$/y,
 		includeEnd: true,

scripts/sequence/parser/Tokeniser_spec.mjs

@@ -1,3 +1,5 @@
+/* eslint-disable max-statements */
+
 import Tokeniser from './Tokeniser.mjs';
 
 describe('Sequence Tokeniser', () => {
@@ -89,6 +91,20 @@ describe('Sequence Tokeniser', () => {
 			]);
 		});
 
+		it('accepts XML tag-like syntax', () => {
+			const input = 'abc <def> >> ghi <<';
+			const tokens = tokeniser.tokenise(input);
+
+			expect(tokens).toEqual([
+				token({s: '', v: 'abc'}),
+				token({s: ' ', v: '<'}),
+				token({s: '', v: 'def>'}),
+				token({s: ' ', v: '>>'}),
+				token({s: ' ', v: 'ghi'}),
+				token({s: ' ', v: '<<'}),
+			]);
+		});
+
 		it('stores line numbers', () => {
 			const input = 'foo bar\nbaz';
 			const tokens = tokeniser.tokenise(input);

scripts/sequence/renderer/Renderer.mjs

@@ -76,6 +76,7 @@ export default class Renderer extends EventObject {
 		this.components = components || getComponents();
 		this.svg = new SVG(new DOMWrapper(document), textSizerFactory);
 		this.knownThemeDefs = new Set();
+		this.knownTextFilterDefs = new Map();
 		this.knownDefs = new Set();
 		this.highlights = new Map();
 		this.collapsed = new Set();
@@ -92,6 +93,7 @@ export default class Renderer extends EventObject {
 			this.prepareMeasurementsStage.bind(this);
 		this.renderStage = this.renderStage.bind(this);
 		this.addThemeDef = this.addThemeDef.bind(this);
+		this.addThemeTextDef = this.addThemeTextDef.bind(this);
 		this.addDef = this.addDef.bind(this);
 	}
 
@@ -150,6 +152,15 @@ export default class Renderer extends EventObject {
 		return namespacedName;
 	}
 
+	addThemeTextDef(name, generator) {
+		const namespacedName = this.namespace + name;
+		if(!this.knownTextFilterDefs.has(name)) {
+			const def = generator().attr('id', namespacedName);
+			this.knownTextFilterDefs.set(name, def);
+		}
+		this.svg.registerTextFilter(name, namespacedName);
+	}
+
 	addDef(name, generator) {
 		let nm = name;
 		let gen = generator;
@@ -531,6 +542,7 @@ export default class Renderer extends EventObject {
 	_reset(theme) {
 		if(theme) {
 			this.knownThemeDefs.clear();
+			this.knownTextFilterDefs.clear();
 			this.themeDefs.empty();
 		}
 
@@ -628,7 +640,11 @@ export default class Renderer extends EventObject {
 		this._reset(themeChanged);
 
 		this.metaCode.nodeValue = sequence.meta.code;
-		this.theme.addDefs(this.addThemeDef);
+		this.svg.resetTextFilters();
+		this.theme.addDefs(this.addThemeDef, this.addThemeTextDef);
+		for(const def of this.knownTextFilterDefs.values()) {
+			def.detach();
+		}
 
 		this.title.set({
 			attrs: Object.assign({
@@ -662,6 +678,10 @@ export default class Renderer extends EventObject {
 		sequence.stages.forEach(this.renderStage);
 		const bottomY = this.checkAgentRange(['[', ']'], this.currentY);
 
+		this.svg.getUsedTextFilterNames().forEach((name) => {
+			this.themeDefs.add(this.knownTextFilterDefs.get(name));
+		});
+
 		const stagesHeight = Math.max(bottomY - this.theme.actionMargin, 0);
 		this.updateBounds(stagesHeight);
 

scripts/sequence/themes/BaseTheme.mjs

@@ -57,8 +57,58 @@ export default class BaseTheme {
 		// No-op
 	}
 
-	addDefs() {
-		// No-op
+	addDefs(builder, textBuilder) {
+		// Thanks, https://stackoverflow.com/a/12263962/1180785
+		// https://bugs.chromium.org/p/chromium/issues/detail?id=603157
+		// https://bugzilla.mozilla.org/show_bug.cgi?id=917766
+		textBuilder('highlight', () => this.svg.el('filter')
+			.add(
+				// Morph makes characters consistent
+				this.svg.el('feMorphology').attrs({
+					'in': 'SourceAlpha',
+					'operator': 'dilate',
+					'radius': '4',
+				}),
+				// Blur+thresh makes edges smooth
+				this.svg.el('feGaussianBlur').attrs({
+					'edgeMode': 'none',
+					'stdDeviation': '3, 1.5',
+				}),
+				this.svg.el('feComponentTransfer').add(
+					this.svg.el('feFuncA').attrs({
+						'intercept': -70,
+						'slope': 100,
+						'type': 'linear',
+					})
+				),
+				// Add colour
+				this.svg.el('feComponentTransfer').add(
+					this.svg.el('feFuncR').attrs({
+						'intercept': 1,
+						'slope': 0,
+						'type': 'linear',
+					}),
+					this.svg.el('feFuncG').attrs({
+						'intercept': 0.9375,
+						'slope': 0,
+						'type': 'linear',
+					}),
+					this.svg.el('feFuncB').attrs({
+						'intercept': 0.09375,
+						'slope': 0,
+						'type': 'linear',
+					}),
+					this.svg.el('feFuncA').attrs({
+						'slope': 0.7,
+						'type': 'linear',
+					})
+				),
+				// Draw text on top
+				this.svg.el('feMerge').add(
+					this.svg.el('feMergeNode'),
+					this.svg.el('feMergeNode').attr('in', 'SourceGraphic')
+				)
+			));
 	}
 
 	getTitleAttrs() {

scripts/sequence/themes/Sketch.mjs

@@ -350,7 +350,7 @@ export default class SketchTheme extends BaseTheme {
 		this.random.reset();
 	}
 
-	addDefs(builder) {
+	addDefs(builder, textBuilder) {
 		builder('sketch_font', () => {
 			const style = this.svg.el('style', null);
 			// Font must be embedded for exporting as SVG / PNG
@@ -362,6 +362,8 @@ export default class SketchTheme extends BaseTheme {
 			);
 			return style;
 		});
+
+		super.addDefs(builder, textBuilder);
 	}
 
 	vary(range, centre = 0) {

scripts/svg/SVG.mjs

@@ -189,12 +189,40 @@ export default class SVG {
 		this.dom = domWrapper;
 		this.body = this.el('svg').attr('xmlns', NS).attr('version', '1.1');
 		const fn = (textSizerFactory || defaultTextSizerFactory);
+		this.textFilters = new Map();
 		this.textSizer = new TextSizerWrapper(fn(this));
 
 		this.txt = this.txt.bind(this);
 		this.el = this.el.bind(this);
 	}
 
+	resetTextFilters() {
+		this.textFilters.clear();
+	}
+
+	registerTextFilter(name, id) {
+		this.textFilters.set(name, {id, used: false});
+	}
+
+	getTextFilter(name) {
+		const filter = this.textFilters.get(name);
+		if(!filter) {
+			return 'none';
+		}
+		filter.used = true;
+		return 'url(#' + filter.id + ')';
+	}
+
+	getUsedTextFilterNames() {
+		const used = [];
+		for(const [name, filter] of this.textFilters) {
+			if(filter.used) {
+				used.push(name);
+			}
+		}
+		return used;
+	}
+
 	linearGradient(attrs, stops) {
 		return this.el('linearGradient')
 			.attrs(attrs)

scripts/svg/SVGTextBlock.mjs

@@ -15,11 +15,14 @@ function populateSvgTextLine(svg, node, formattedLine) {
 		throw new Error('Invalid formatted text line: ' + formattedLine);
 	}
 	formattedLine.forEach(({text, attrs}) => {
+		let element = text;
 		if(attrs) {
-			node.add(svg.el('tspan').attrs(attrs).add(text));
-		} else {
-			node.add(text);
+			element = svg.el('tspan').attrs(attrs).add(text);
+			if(attrs.filter) {
+				element.attr('filter', svg.getTextFilter(attrs.filter));
+			}
 		}
+		node.add(element);
 	});
 }
 

scripts/svg/SVGTextBlock_spec.mjs

@@ -76,6 +76,17 @@ describe('SVGTextBlock', () => {
 				.toEqual('foo<tspan zig="zag">bar</tspan>');
 		});
 
+		it('converts filter attributes using the registered filters', () => {
+			svg.registerTextFilter('foo', 'local-foobar');
+			block.set({formatted: [[
+				{text: 'foo'},
+				{attrs: {'filter': 'foo'}, text: 'bar'},
+			]]});
+
+			expect(hold.childNodes[0].innerHTML)
+				.toEqual('foo<tspan filter="url(#local-foobar)">bar</tspan>');
+		});
+
 		it('re-uses text nodes when possible, adding more if needed', () => {
 			block.set({formatted: [[{text: 'foo'}], [{text: 'bar'}]]});
 			const [line0, line1] = hold.childNodes;

spec/image/ImageRegion.mjs

@@ -461,9 +461,20 @@ ImageRegion.loadURL = function(url, size = {}) {
 };
 
 ImageRegion.loadSVG = function(svg, size = {}) {
-	const blob = new Blob([svg], {type: 'image/svg+xml'});
+	// Safari workaround:
+	// Tweak SVG size directly rather than resizing image to keep quality high
+	const resolution = size.resolution || 1;
+	const svgCode = svg.replace(
+		/<svg width="([^"]+)" height="([^"]+)"/,
+		(m, w, h) => (
+			'<svg width="' + (w * resolution) +
+			'" height="' + (h * resolution) + '"'
+		)
+	);
+
+	const blob = new Blob([svgCode], {type: 'image/svg+xml'});
 	const url = URL.createObjectURL(blob);
-	return ImageRegion.loadURL(url, size)
+	return ImageRegion.loadURL(url, Object.assign({}, size, {resolution: 1}))
 		.then((region) => {
 			URL.revokeObjectURL(url);
 			return region;

spec/images/Markdown.svg

@@ -1,3 +1,5 @@
-<svg width="86.02510070800781" height="98"  xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="-43.012550354003906 -93 86.02510070800781 98"><metadata>title "Foo **Bar**
+<svg width="96.69921875" height="124" xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="-48.349609375 -119 96.69921875 124"><metadata>title "Foo **Bar**
 _Baz_ `Zig`
-**_`Zag`_**"</metadata><defs></defs><defs><mask id="R0FullMask" maskUnits="userSpaceOnUse"><rect fill="#FFFFFF" height="98" width="86.02510070800781" x="-43.012550354003906" y="-93"></rect></mask><mask id="R0LineMask" maskUnits="userSpaceOnUse"><rect fill="#FFFFFF" height="98" width="86.02510070800781" x="-43.012550354003906" y="-93"></rect></mask></defs><g></g><g><text x="0" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" class="title" y="-68">Foo <tspan font-weight="bolder">Bar</tspan></text><text x="0" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" class="title" y="-42"><tspan font-style="italic">Baz</tspan> <tspan font-family="Courier New,Liberation Mono,monospace">Zig</tspan></text><text x="0" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" class="title" y="-16"><tspan font-style="italic" font-weight="bolder" font-family="Courier New,Liberation Mono,monospace">Zag</tspan></text></g><g></g><g mask="url(#R0FullMask)"><g mask="url(#R0LineMask)"></g><g></g><g></g></g></svg>
+**_`Zag`_**
+&lt;highlight&gt;Back&lt;/highlight&gt; &lt;red&gt;Text&lt;/red&gt;"
+</metadata><defs><filter id="R0highlight"><feMorphology in="SourceAlpha" operator="dilate" radius="4"></feMorphology><feGaussianBlur edgeMode="none" stdDeviation="3, 1.5"></feGaussianBlur><feComponentTransfer><feFuncA intercept="-70" slope="100" type="linear"></feFuncA></feComponentTransfer><feComponentTransfer><feFuncR intercept="1" slope="0" type="linear"></feFuncR><feFuncG intercept="0.9375" slope="0" type="linear"></feFuncG><feFuncB intercept="0.09375" slope="0" type="linear"></feFuncB><feFuncA slope="0.7" type="linear"></feFuncA></feComponentTransfer><feMerge><feMergeNode></feMergeNode><feMergeNode in="SourceGraphic"></feMergeNode></feMerge></filter></defs><defs><mask id="R0FullMask" maskUnits="userSpaceOnUse"><rect fill="#FFFFFF" height="124" width="96.69921875" x="-48.349609375" y="-119"></rect></mask><mask id="R0LineMask" maskUnits="userSpaceOnUse"><rect fill="#FFFFFF" height="124" width="96.69921875" x="-48.349609375" y="-119"></rect></mask></defs><g></g><g><text x="0" class="title" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" y="-94">Foo <tspan font-weight="bolder">Bar</tspan></text><text x="0" class="title" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" y="-68"><tspan font-style="italic">Baz</tspan> <tspan font-family="Courier New,Liberation Mono,monospace">Zig</tspan></text><text x="0" class="title" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" y="-42"><tspan font-style="italic" font-weight="bolder" font-family="Courier New,Liberation Mono,monospace">Zag</tspan></text><text x="0" class="title" font-family="Helvetica,Arial,Liberation Sans,sans-serif" font-size="20" line-height="1.3" text-anchor="middle" y="-16"><tspan filter="url(#R0highlight)">Back</tspan> <tspan fill="#DD0000">Text</tspan></text></g><g></g><g mask="url(#R0FullMask)"><g mask="url(#R0LineMask)"></g><g></g><g></g></g></svg>

web/lib/editor.js

@@ -266,6 +266,16 @@
 			preview: 'A -> B: `mono`',
 			title: 'Monospace markdown',
 		},
+		{
+			code: '<red>{text}</red>',
+			preview: 'A -> B: <red>red</red>',
+			title: 'Red markdown',
+		},
+		{
+			code: '<highlight>{text}</highlight>',
+			preview: 'A -> B: <highlight>highlight</highlight>',
+			title: 'Highlight markdown',
+		},
 		{
 			code: '{Agent} is red',
 			preview: 'headers box\nA is red\nbegin A',
@@ -479,7 +489,9 @@
 		}
 
 		detach() {
-			this.element.parentNode.removeChild(this.element);
+			if(this.element.parentNode) {
+				this.element.parentNode.removeChild(this.element);
+			}
 			return this;
 		}
 	}

web/scripts/interface/ComponentsLibrary.mjs

@@ -263,6 +263,16 @@ export default [
 		preview: 'A -> B: `mono`',
 		title: 'Monospace markdown',
 	},
+	{
+		code: '<red>{text}</red>',
+		preview: 'A -> B: <red>red</red>',
+		title: 'Red markdown',
+	},
+	{
+		code: '<highlight>{text}</highlight>',
+		preview: 'A -> B: <highlight>highlight</highlight>',
+		title: 'Highlight markdown',
+	},
 	{
 		code: '{Agent} is red',
 		preview: 'headers box\nA is red\nbegin A',