On 2024-04-26 21:52, Christian Ehrlicher via Development wrote:
Hello,
I'm currently trying to investigate a painting problem within the
windowsvista / common style:
QImage img(7, 7, QImage::Format_ARGB32_Premultiplied);
QPolygon poly{ QPoint(1, 1), {5, 1}, {3, 5} };
QPainter p();
p.setPen(Qt::NoPen);
p.setBrush(QColor(Qt::black));
p.drawPolygon(poly);
p.setPen(QColor(0, 255, 0, 128));
p.drawPoints(poly.data(), poly.size());
p.end();
img.save("output.png");
This code should draw a small down arrow (e.g. for a QPushButton with a
QMenu attached) and should look similar to this:
0123456
0
1 X
2 XXX
3 XXX
4 X
5 X
6
But the outcome is this:
0123456
0
1
2 XX
3 XX
4
5
6
Setting a non-cosmetic pen at least result in painting of all three
corners but gives a non-symmetric triangle:
0123456
0
1 X
2
3 XXX
4 XX
5 X
6
I've no idea how to draw this triangle the way I want (and everyone is
satisfied with the outcome). Do you have any ideas?
Thx,
Christian
Hi, I think the QPainter draws very poorly using direct polygon paths.
You could try going via a QPainterPath, say:
QImage img(7, 7, QImage::Format_ARGB32_Premultiplied);
img.fill(QColor(0, 255, 0, 128)); // to be sure the img contains
no junk values
QPolygon poly{ QPoint(1, 1), {5, 1}, {3, 5} };
QPainter p();
p.setPen(Qt::NoPen);
p.setBrush(QColor(Qt::black));
p.setPen(QColor(0, 255, 0, 128));
QPainterPath path;
path.addPolygon(poly);
p.drawPath(path);
p.end();
img.save("output.png");
Rgrds Henry
--
Development mailing list
Development@qt-project.org
https://lists.qt-project.org/listinfo/development
