Just let Qt do its work. If by drawing directly on QWidget you mean subclassing it and rewriting its Paint() method - don't do it unless you absolutely have to. Or, when you need to provide a delegate for a view.
So far I've not had the necessity to dive that deep.
And since you can display (and scale) images and videos using QLabel, push buttons can be readily supplied with an icon... I just had not need.
Then again, your needs might differ.

Solved it by changing my drawline to: painter.drawLine(QPointF(pX1, pY1), QPointF(pX2, pY2));

Thank you, I think this will do just perfect!

@Bonnie

Thank you, setting it before drawPixmap works. I don't need any smoothing so nearest neighbor resize is fine for me.

@mrjj Thanks, so I hit the limit. I'll try not to go over that.

@Mquaza said in QPainter drawRects without draging a line behind:

How do you make it so, that 2 rectangles are moving across the scene?

I would say change their coordinates?

@SamurayH The solution is perfect to me. Thank you very much!

@mrjj Thank you for your answer. So I tested to remove the text rectangle passed to the drawContents() function, and indeed the global clipping was applied instead.

@mrjj
Thank you sir for helping me and direction. I am able to solve this issue by

setting the clipping area properly on graph. Use QWidget::update() instead of QWidget::repaint().

Then maybe QTreeView::drawBranches is what you are looking for.

@SGaist
Ok that sounds a bit bad like -
"delete while in use" situation.
So it seems plausible it could crash from that in some cases.

@kent-dorfman Thanks and will try out those methods also.

Some of the reasons are right there in the documentation: QPainter::begin().
Generally speaking begin() returns false when the underlying resources are unavailable - another painter is active on that device, trying to paint to a null device or image, underlying paint engine is uninitialized or non existing etc. For end() it's similar - either the painter in not active on any device or the underlying paint engine failed to end the operation for whatever reason.

There is no API for getting the reason of failure of any of those as it would be hard to make one considering there are different paint engines and you can even make one yourself. It would have to be something really generic like a string, and having users parse that and basically expect every possible reason on every supported platform would not be a good API.

You won't get a paint event at all during drag'n'drop I would guess since the cursor is not directly painted by Qt when I'm correct.

kind of shooting in the dark here, but remember that the painter coordinate system can be scaled, rotated, and new origin set. Try explicitly defining the coordinate system...Also, if your coordinates are floating point then you have to deal with floating point roundoff error.

@Staslend if your issue is solved, please don't forget to mark your post as such! Thanks.

Ok solved

It appears that a GLOBAL surface setInterval overrides the setIntervals I did on my glWidget. Kinda weird that the global one overrides local one if local one was specified, is this a bug ?

format.setSwapInterval(0); QSurfaceFormat::setDefaultFormat(format);

overrides on widget >

QSurfaceFormat format; format.setSwapInterval(0); setFormat(format);

Hi
Well to get below the QWTPlot plot would
be QWTPlotptr->y() + QWTPlotptr->height()
However, a more solid approach could be to use a QLabel as
a canvas using a pixmap. That way, its very easy to position even if using layouts to make
GUI auto adjust to different screen sizes.

void PaintShapes() { // take size of label int h = ui->label->height(); int w = ui->label->width(); // make a pixmap of the wanted size QPixmap pix(w, h); // assign painter to it so we can paint on it QPainter paint(&pix); // fill it pix.fill( Qt::white ); // paint on canvas paint.setPen(QColor(0, 0, 0, 255)); paint.drawRect(0, 0, w, h); ..other paint operations-.. // set the pixmap to the label so its shown. ui->label->setPixmap(pix); }