Proper path-text halo drawing

src/style.cpp

@@ -230,6 +230,9 @@ Style::Layer::Paint::Paint(const QJsonObject &json)
 
 	// text
 	_textColor = FunctionC(json["text-color"]);
+	_textHaloColor = FunctionC(json["text-halo-color"], QColor());
+	_textHaloWidth = FunctionF(json["text-halo-width"]);
+	_textHaloBlur = FunctionF(json["text-halo-blur"]);
 }
 
 QPen Style::Layer::Paint::pen(Type type, int zoom) const
@@ -511,6 +514,7 @@ void Style::Layer::setTextProperties(Tile &tile) const
 	t.setFont(_layout.font(zoom));
 	t.setSymbolPlacement(_layout.symbolPlacement(zoom));
 	t.setRotationAlignment(_layout.textRotationAlignment(zoom));
+	t.setHalo(_paint.halo(zoom));
 }
 
 void Style::Layer::addSymbol(Tile &tile, const QPainterPath &path,

src/style.h

@@ -137,9 +137,13 @@ private:
 			  const;
 			qreal opacity(Layer::Type type, int zoom) const;
 			bool antialias(Layer::Type type, int zoom) const;
+			Text::Halo halo(int zoom) const
+			  {return Text::Halo(_textHaloColor.value(zoom),
+			  _textHaloWidth.value(zoom), _textHaloBlur.value(zoom));}
 
 		private:
 			FunctionC _textColor;
+			FunctionC _textHaloColor;
 			FunctionC _lineColor;
 			FunctionC _fillColor;
 			FunctionC _fillOutlineColor;
@@ -147,6 +151,8 @@ private:
 			FunctionF _fillOpacity;
 			FunctionF _lineOpacity;
 			FunctionF _lineWidth;
+			FunctionF _textHaloWidth;
+			FunctionF _textHaloBlur;
 			FunctionB _fillAntialias;
 			QVector<qreal> _lineDasharray;
 			FunctionS _fillPattern;

src/text.cpp

@@ -56,6 +56,7 @@ void Text::addLabel(const QString &text, const QImage &icon,
 	}
 
 	ti->setPen(_pen);
+	ti->setHalo(_halo);
 	addItem(ti);
 
 	QList<TextItem*> ci = collidingItems(ti);

src/text.h

@@ -34,6 +34,22 @@ public:
 		Auto
 	};
 
+	class Halo {
+	public:
+		Halo() : _width(0), _blur(0) {}
+		Halo(const QColor &color, qreal width, qreal blur)
+		  : _color(color), _width(width), _blur(blur) {}
+
+		const QColor &color() const {return _color;}
+		qreal width() const {return _width;}
+		qreal blur() const {return _blur;}
+
+	private:
+		QColor _color;
+		qreal _width;
+		qreal _blur;
+	};
+
 	Text(const QSize &size) : _sceneRect(QRectF(QPointF(0, 0), size)) {}
 	~Text();
 
@@ -45,6 +61,7 @@ public:
 	void setSymbolPlacement(SymbolPlacement placement);
 	void setRotationAlignment(RotationAlignment alignment)
 	  {_alignment = alignment;}
+	void setHalo(const Halo &halo) {_halo = halo;}
 
 	void addLabel(const QString &text, const QImage &icon,
 	  const QPainterPath &path);
@@ -65,6 +82,7 @@ private:
 	RotationAlignment _alignment;
 	QFont _font;
 	QPen _pen;
+	Halo _halo;
 };
 
 #endif // TEXT_H

src/textitem.h

@@ -6,6 +6,7 @@
 #include <QPen>
 #include <QFont>
 #include <QRectF>
+#include "text.h"
 
 class QPainter;
 
@@ -19,7 +20,9 @@ public:
 	const QString &text() const {return _text;}
 	const QFont &font() const {return _font;}
 	const QPen &pen() const {return _pen;}
+	const Text::Halo &halo() const {return _halo;}
 	void setPen(const QPen &pen) {_pen = pen;}
+	void setHalo(const Text::Halo &halo) {_halo = halo;}
 
 	virtual QPainterPath shape() const = 0;
 	virtual QRectF boundingRect() const = 0;
@@ -37,6 +40,7 @@ private:
 	QString _text;
 	QFont _font;
 	QPen _pen;
+	Text::Halo _halo;
 	bool _visible;
 };
 

src/textpathitem.cpp

@@ -166,10 +166,35 @@ void TextPathItem::paint(QPainter *painter) const
 	qreal percent = (1.0 - factor) / 2.0;
 
 	painter->setFont(font());
-	painter->setPen(pen());
 
 	QTransform t = painter->transform();
 
+	if (halo().color().isValid() && halo().width() > 0) {
+		painter->setPen(halo().color());
+		for (int i = 0; i < text().size(); i++) {
+			QPointF point = _path.pointAtPercent(percent);
+			qreal angle = _path.angleAtPercent(percent);
+
+			painter->translate(point);
+			painter->rotate(-angle);
+			painter->drawText(QPoint(-1, fm.descent() - 1), text().at(i));
+			painter->drawText(QPoint(1, fm.descent() + 1), text().at(i));
+			painter->drawText(QPoint(-1, fm.descent() + 1), text().at(i));
+			painter->drawText(QPoint(1, fm.descent() -1), text().at(i));
+			painter->drawText(QPoint(0, fm.descent() - 1), text().at(i));
+			painter->drawText(QPoint(0, fm.descent() + 1), text().at(i));
+			painter->drawText(QPoint(-1, fm.descent()), text().at(i));
+			painter->drawText(QPoint(1, fm.descent()), text().at(i));
+			painter->setTransform(t);
+
+			int width = fm.charWidth(text(), i);
+			percent += ((qreal)width / (qreal)textWidth) * factor;
+		}
+
+		percent = (1.0 - factor) / 2.0;
+	}
+
+	painter->setPen(pen());
 	for (int i = 0; i < text().size(); i++) {
 		QPointF point = _path.pointAtPercent(percent);
 		qreal angle = _path.angleAtPercent(percent);

src/textpointitem.cpp

@@ -128,9 +128,10 @@ void TextPointItem::paint(QPainter *painter) const
 	//painter->drawRect(_boundingRect);
 
 	QRectF textRect;
+	bool hasHalo = halo().color().isValid() && halo().width() > 0;
 
 	if (!_icon.isNull()) {
-		textRect = (_anchor != Text::Center)
+		textRect = (_anchor != Text::Center || hasHalo)
 		  ? computeTextRect(true) : _boundingRect;
 #ifdef ENABLE_HIDPI
 		painter->drawImage(_pos - QPointF(_icon.width()
@@ -141,9 +142,33 @@ void TextPointItem::paint(QPainter *painter) const
 		  _icon.height() / 2), _icon);
 #endif // ENABLE_HIDPI
 	} else
-		textRect = _boundingRect;
+		textRect = hasHalo ? computeTextRect(true) : _boundingRect;
 
-	painter->setFont(font());
-	painter->setPen(pen());
-	painter->drawText(textRect, FLAGS, text());
+
+	if (hasHalo) {
+		QRect ir(textRect.toRect());
+		QImage img(ir.size(), QImage::Format_ARGB32_Premultiplied);
+		img.fill(Qt::transparent);
+		QPainter ip(&img);
+		ip.setPen(halo().color());
+		ip.setFont(font());
+		ip.drawText(img.rect(), FLAGS, text());
+
+		painter->drawImage(ir.x() - 1, ir.y() - 1, img);
+		painter->drawImage(ir.x() + 1, ir.y() + 1, img);
+		painter->drawImage(ir.x() - 1, ir.y() + 1, img);
+		painter->drawImage(ir.x() + 1, ir.y() - 1, img);
+		painter->drawImage(ir.x(), ir.y() - 1, img);
+		painter->drawImage(ir.x(), ir.y() + 1, img);
+		painter->drawImage(ir.x() - 1, ir.y(), img);
+		painter->drawImage(ir.x() + 1, ir.y(), img);
+
+		painter->setFont(font());
+		painter->setPen(pen());
+		painter->drawText(ir, FLAGS, text());
+	} else {
+		painter->setFont(font());
+		painter->setPen(pen());
+		painter->drawText(textRect, FLAGS, text());
+	}
 }