@TenG Be aware that not all of Qt modules are supported in WASM. Before anything, check the list at https://doc.qt.io/qt-5/wasm.html#supported-qt-modules against what is in your app. For example, it doesn't do databases, you can't access the local file system, and so on. Also I noticed this time that it requires a Qt static build, but maybe you have to have that for iOS anyway, I don't know. If it works for you it's a really simple solution compared to rewriting anything. Just check out the gotchas.

Thanks for the code ! You can use the Q_OS_XXX macros to ifdef your code.

so write a test program, meter the performance of canvas writes vs out-of-bounds writes, and report back.

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); }

@Niagarer Good found. :)

You can make a "container widget" that will handle the showing of the label properly.

@Zhukov said in Рисование линии Qt: Как передать точки x,y,x1,y1 в paintEvent()? Как показали выше: сохранить координаты в полях класса, вызвать update() (repaint лучше не юзать без особых причин) и использовать эти поля в paintEvent() Как вариант, можно использовать QPainterPath или даже QPicture, это хорошо подойдет если планируется рисовать много линий и добавлять/убирать их в процессе работы приложения. Еще можно нарисовать линии в QImage и затем рисовать получившуюся картинку в paintEvent(), хорошо подойдет для реализации растрового редактора типа MS Paint, но будет привязка к конкретным размерам картинки в пикселях. Как использовать paintEvent() в любой момент? Никак, paintEvent вызывается в моменты перерисовки окна графической системой. Если вызвать repaint(), то эта перерисвока произойдет практически сразу же, но лучше не делать код, зависящий от предположения мгновенной перерисовки, и использовать update

@onurcevik Did you ever figure the solution for this? Working on it now

Hi @f.serreau I have tested your example, and it works correctly with no errors. I tested it on Windows 10 (Fall Update), MS VS2017 and Qt 5.11.0.

Sorry, I don't have the XPS printer available. Can you check whether you have the same result with the QPdfWriter class ?

@mdma2 Can you post the full code of this short example, so that it can be tried out immediately using simple copy/paste...

In your MyView::paintEvent write QPainter painter(viewport()); instead of QPainter painter(this);.

Hi Arthur, Sorry you did not get any feedback for your issue after so long, shows there must be a minimal use or understanding of this class. Did you get help or find solution you can share. I'm also trying to find help using this class and lack of doc is still there I'm afraid. One possibility is to look at KoTextDocumentLayout.h and cpp files, these might help with some information. https://github.com/JeremiasE/KFormula/blob/gsoc/libs/kotext/KoTextDocumentLayout.h

@dalishi You should not mix painter and gl calls like that. You should put gl calls between calls to beginNativePainting() and endNativePainting(), which are painter functions. It might also help to save the painter state before and restore it after depending on how it messes up your gl stuff. the docs here tell you what the painter does to the states.

Ok, I will try that... Maybe I should have been more clearly what I intend to get... I had it all working already, just without the scaling issue I get camera images and I let opencv compute min/max values and a centerpoint. Somethimes the camera is rotated in a undesired position so the user should be able to rotate the view, including the measurepoints, and more complex including the point values so that the stay at the points but do not rotate staying readable... I keep trying with qpainter draw

@VRonin Yes, they are, but the pixmap is just grabbed QGraphicsView's content using grab() method.

@mrjj Thanks! I'll look into that. I got another reply from stackoverflow which I will also give a shot. I'll keep everyone in both forums posted as soon as I have some results.

Hi, Glad you found out and thanks for sharing ! What version of Qt are you using ? On which platform ? Did you check the bug report system to see if it's something known ?

It uses the raster engine. See here for historical informations.

The following solution worked: #include "mainwindow.h" #include "ui_mainwindow.h" MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWindow) { ui->setupUi(this); } MainWindow::~MainWindow() { delete ui; } void MainWindow::paintEvent(QPaintEvent *event) { QPainter painter(this); QFont font = painter.font (); font.setFamily ("Arial"); font.setPixelSize (25); painter.setFont (font); painter.setPen (Qt::white); QRect rect(100, 120, 200, 50); painter.setBrush (Qt::blue); painter.drawRect (rect); painter.drawText (rect, Qt::AlignCenter, tr("Record deleted.")); painter.end(); QTimer::singleShot(3000,this,&MainWindow::hideRect); update(); } Thank you for your help.

Yeah i feel like i do sudo apt-get update && upgrade at least once a day. I just checked about SIP and i compiled it from source but i cant remember if i actually used the command make and make install. Does that mean i have to reinstall pyqt5 again? I guess i just open a new thread. Thanks for all the help @SGaist