Dynamic StarWidget metrics

The default IMG_SIZE and SPACING in the StarWidget are not appropriate
for HiDPI displays. Replace them with StarMetrics which are
auto-computed from the (default) font size (which Qt determines from the
display DPI settings).

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/modeldelegates.cpp

@@ -50,17 +50,19 @@ void StarWidgetsDelegate::paint(QPainter *painter, const QStyleOptionViewItem &o
 	painter->setRenderHint(QPainter::Antialiasing, true);
 	const QPixmap active = QPixmap::fromImage(StarWidget::starActive());
 	const QPixmap inactive = QPixmap::fromImage(StarWidget::starInactive());
+	const StarMetrics& metrics = StarWidget::metrics();
 
 	for (int i = 0; i < rating; i++)
-		painter->drawPixmap(option.rect.x() + i * IMG_SIZE + SPACING, option.rect.y() + deltaY, active);
+		painter->drawPixmap(option.rect.x() + i * metrics.size + metrics.spacing, option.rect.y() + deltaY, active);
 	for (int i = rating; i < TOTALSTARS; i++)
-		painter->drawPixmap(option.rect.x() + i * IMG_SIZE + SPACING, option.rect.y() + deltaY, inactive);
+		painter->drawPixmap(option.rect.x() + i * metrics.size + metrics.spacing, option.rect.y() + deltaY, inactive);
 	painter->restore();
 }
 
 QSize StarWidgetsDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
 {
-	return QSize(IMG_SIZE * TOTALSTARS + SPACING * (TOTALSTARS - 1), IMG_SIZE);
+	const StarMetrics& metrics = StarWidget::metrics();
+	return QSize(metrics.size * TOTALSTARS + metrics.spacing * (TOTALSTARS - 1), metrics.size);
 }
 
 ComboBoxDelegate::ComboBoxDelegate(QAbstractItemModel *model, QObject *parent) : QStyledItemDelegate(parent), model(model)

qt-ui/starwidget.cpp

@@ -11,6 +11,7 @@
 
 QImage StarWidget::activeStar;
 QImage StarWidget::inactiveStar;
+StarMetrics StarWidget::imgMetrics = { -1, -1 };
 
 const QImage& StarWidget::starActive()
 {
@@ -22,6 +23,11 @@ const QImage& StarWidget::starInactive()
 	return inactiveStar;
 }
 
+const StarMetrics& StarWidget::metrics()
+{
+	return imgMetrics;
+}
+
 int StarWidget::currentStars() const
 {
 	return current;
@@ -33,7 +39,7 @@ void StarWidget::mouseReleaseEvent(QMouseEvent *event)
 		return;
 	}
 
-	int starClicked = event->pos().x() / IMG_SIZE + 1;
+	int starClicked = event->pos().x() / imgMetrics.size + 1;
 	if (starClicked > TOTALSTARS)
 		starClicked = TOTALSTARS;
 
@@ -53,10 +59,10 @@ void StarWidget::paintEvent(QPaintEvent *event)
 	QPixmap inactive = QPixmap::fromImage(starInactive());
 
 	for (int i = 0; i < current; i++)
-		p.drawPixmap(i * IMG_SIZE + SPACING, 0, active);
+		p.drawPixmap(i * imgMetrics.size + imgMetrics.spacing, 0, active);
 
 	for (int i = current; i < TOTALSTARS; i++)
-		p.drawPixmap(i * IMG_SIZE + SPACING, 0, inactive);
+		p.drawPixmap(i * imgMetrics.size + imgMetrics.spacing, 0, inactive);
 
 	if (hasFocus()) {
 		QStyleOptionFocusRect option;
@@ -77,14 +83,25 @@ StarWidget::StarWidget(QWidget *parent, Qt::WindowFlags f) : QWidget(parent, f),
 	current(0),
 	readOnly(false)
 {
+	// compute image size, by rounding the font height to the nearest multiple of 16
+	if (imgMetrics.size == -1) {
+		int height = QFontMetrics(parent->font()).height();
+		imgMetrics.size = (height + 8)/16;
+		imgMetrics.size *= 16;
+		// enforce a minimum size
+		if (imgMetrics.size < 16)
+			imgMetrics.size = 16;
+		imgMetrics.spacing = imgMetrics.size/8;
+	}
+
 	if (activeStar.isNull()) {
 		QSvgRenderer render(QString(":star"));
-		QPixmap renderedStar(IMG_SIZE, IMG_SIZE);
+		QPixmap renderedStar(imgMetrics.size, imgMetrics.size);
 
 		renderedStar.fill(Qt::transparent);
 		QPainter painter(&renderedStar);
 
-		render.render(&painter, QRectF(0, 0, IMG_SIZE, IMG_SIZE));
+		render.render(&painter, QRectF(0, 0, imgMetrics.size, imgMetrics.size));
 		activeStar = renderedStar.toImage();
 	}
 	if (inactiveStar.isNull()) {
@@ -113,7 +130,7 @@ QImage grayImage(const QImage& coloredImg)
 
 QSize StarWidget::sizeHint() const
 {
-	return QSize(IMG_SIZE * TOTALSTARS + SPACING * (TOTALSTARS - 1), IMG_SIZE);
+	return QSize(imgMetrics.size * TOTALSTARS + imgMetrics.spacing * (TOTALSTARS - 1), imgMetrics.size);
 }
 
 void StarWidget::setReadOnly(bool r)

qt-ui/starwidget.h

@@ -4,11 +4,14 @@
 #include <QWidget>
 
 enum StarConfig {
-	SPACING = 2,
-	IMG_SIZE = 16,
 	TOTALSTARS = 5
 };
 
+struct StarMetrics {
+	int size;
+	int spacing;
+};
+
 class StarWidget : public QWidget {
 	Q_OBJECT
 public:
@@ -19,6 +22,7 @@ public:
 
 	static const QImage& starActive();
 	static const QImage& starInactive();
+	static const StarMetrics& metrics();
 
 signals:
 	void valueChanged(int stars);
@@ -41,6 +45,7 @@ private:
 
 	static QImage activeStar;
 	static QImage inactiveStar;
+	static StarMetrics imgMetrics;
 };
 
 #endif // STARWIDGET_H