How to create a QLinearGradient?

[Kattia]

What's wrong in the way i'm creating the QLinearGradient?
At qDebug() << gradient; it output: QBrush(QColor(Invalid),LinearGradientPattern)

int main(int argc, char* argv[]) {
	QApplication app(argc, argv);

	QLinearGradient gradient;
	QString gradientString = "background-color: qlineargradient(spread:pad, x1:0, y1:0, x2:1, y2:0, stop:0 rgba(15, 21, 255, 155), stop:1 rgba(126, 22, 224, 155));";
	QWidget* widget = new QWidget;
	widget->setStyleSheet(gradientString);
	widget->setWindowTitle("StyleSheet");
	widget->show();
	
        // Parse the string to create a QLinearGradient

	// Remove the "qlineargradient(" and ")" parts
	gradientString.replace("background-color: qlineargradient(", "");
	gradientString.chop(2);

	// Extract the start and end points
	QRegularExpression rx("x1:([\\d.]+), y1:([\\d.]+), x2:([\\d.]+), y2:([\\d.]+)");
	QRegularExpressionMatch match = rx.match(gradientString);
	if (match.hasMatch())
	{
		float x1 = match.captured(1).toFloat();
		float y1 = match.captured(2).toFloat();
		float x2 = match.captured(3).toFloat();
		float y2 = match.captured(4).toFloat();
		qDebug() << "x1:" << x1 << "y1:" << y1 << "\nx2:" << x2 << "y2:" << y2 << "\n";

		gradient = QLinearGradient(QPointF(x1, y1), QPointF(x2, y2));

		// Extract the color stops
		QRegularExpression rxStop("stop:([\\d.]+) rgba\\((\\d+), (\\d+), (\\d+), (\\d+)\\)");
		int pos = 0;
		while ((match = rxStop.match(gradientString, pos)).hasMatch())
		{
			float stop = match.captured(1).toFloat();
			int r = match.captured(2).toInt();
			int g = match.captured(3).toInt();
			int b = match.captured(4).toInt();
			int a = match.captured(5).toInt();

			qDebug().nospace() << "stop: " << stop << " rgba(" << r << "," << g << "," << b << "," << a << ")\n";

			// Check if the color values are valid
			if (r >= 0 && r <= 255 && g >= 0 && g <= 255 && b >= 0 && b <= 255 && a >= 0 && a <= 255)
				gradient.setColorAt(stop, QColor(r, g, b, a));
			else
				qDebug() << "Invalid color values";

			pos = match.capturedEnd();
		}
		qDebug() << gradient;
	}

	widget = new QWidget;
	QPalette palette;
	palette.setBrush(widget->backgroundRole(), QBrush(gradient));
	widget->setPalette(palette);
	widget->setWindowTitle("Palette");
	widget->show();

	return app.exec();
}

[KenAppleby 0]

@Kattia said in How to create a QLinearGradient?:

At qDebug() << gradient; it output: QBrush(QColor(Invalid),LinearGradientPattern)

I think this just means that the brush has been set with a gradient and no a fill colour. You can ignore this.

The constructor for QLinearGradient takes pixel dimensions. So you are creating one that is just 1 pixel wide and 0 pixels high. Try something like:

gradient = QLinearGradient(QPointF(0.0, 0.0), widget->rect().bottomRight());

[Ketan__Patel__0011]

You can see this video about QLinearGradient

https://youtu.be/hK5dP2Onw9E?si=W19327qJOEzO8Aw5