Stylesheet qlineargradient rendering is incorrect

This testcase: gradients.cpp shows that

background-color: qlineargradient(...)

does not render the gradient correctly. Compare with the QPainter code, which renders the gradient as expected:

The problem comes from QGradient::ObjectBoundingMode (which is what src/gui/text/qcssparser.cpp uses), since the issue can actually be reproduced by changing the QPainter code to say

QLinearGradient gradient(0.50, 1, 0.58, 0);
gradient.setCoordinateMode(QGradient::ObjectBoundingMode); 

Note that using ObjectMode (given that ObjectBoundingMode is actually deprecated) makes no difference (which makes sense given that there's no transform applied to the painter).

From the documentation I assume this mode simply means "please multiply with the width and height of the object, respectively", but looking at QPainterPrivate::drawStretchedGradient and stretchGradientToUserSpace() in qpainter.cpp, it seems more complicated than that...