I am writing very simple vector tool for graphics. I have rich text edited in QTextEditor. I also have class extending QGraphicsScene where all my drawings are. I want to somehow paint text from QTextEditor on this scene? What are my options?
Best Regards!
You can use QPainter::drawtext() method. basically you get a painter of the area you want to draw in and then use this method to draw your text.
QPainter p(this);
p.drawText(rect(), Qt::AlignCenter, "Hello World!");
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I am writing a little program in C++ with Qt.
I have a QGridLayout with 3*3 QWidget. In each QWidget, I have a QVBoxLayout.
Within that QVBoxLayout I need to put a certain number of black and white rectangles.
For now, I use QWidgets for these rectangle and I apply a background-color to get the white and the black ones.
I saw in the documentation something about a Rectangle class that is linked with QtQuick and I don't really want to go into that.
Thanks for your answers,
I wouldn't bother with the layout and widgets unless you actually need interactive objects for each square. Just overload the paintEvent member of the widget you are using that contains the grid layout and use the QPainter object and call fillRect.
To get an outline around a widget, use a QFrame. Also QLabel subclasses QFrame. There are a lot of examples of using QFrame in the documentation.
Hope that helps.
I guess there are lots of ways to achieve this. I have an application in which a video stream is shown over a custom QWidget that I have subclasses from QLabel, and painting frames using QPainter. Given that, is it possible to let the user to drag a rectangle over the image and retrieve the coordinates? The requirement is that the rectangle must be visible during the dragging.
Thanks in advance,
Have a look at QRubberBand. It allows you to place such a rect on top of e.g. a QLabel. The documentation also contains an example how to move and resize the rubberband using the mouse.
the QGraphicsView has the void setRubberBandSelectionMode ( Qt::ItemSelectionMode mode ) but i dont know if the QLabel has some similar feature ...
maybe you have to draw your own rectangle while the user drags the rectangle and catch it on mouserelease
soo long zai
In you widget you could track mouse pressed and released events and track where on the widget the corners of the selection rect are. For drawing the rectangle, I'd take a look at QStyle::drawFocusRect. I think the intent of that is to draw a rect you'd be able to see regardless of what's behind it.
Or perhaps try this:
QStylePainter painter(this);
QStyleOptionFocusRect option;
option.initFrom(this);
option.backgroundColor = palette().color(QPalette::Background);
painter.drawPrimitive(QStyle::PE_FrameFocusRect, option);
I want to design a new QIcon and want it to look like a fixed text with a rounded rectangle around it
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The icon is supposed to scale without the "pixel-blocks" effect when painting on a QPainter that eventually has a scale transformation applied (for example when I paint into a widget that is part of a QGraphicsView with a scale applied on its scene).
Therefor, I have difficulties knowing how I should paint my QIcon. If I do it in the following way, I will paint a QPixmap that always has a fixed amount of pixels, thus introducing the pixel-blocks effect inevitably when the scale is large enough
void MyWidget::drawIcon(QPainter *painter, QPoint pos) {
QPixmap pixmap = icon.pixmap(QSize(22, 22),
isEnabled() ? QIcon::Normal
: QIcon::Disabled,
isChecked() ? QIcon::On
: QIcon::Off);
painter->drawPixmap(pos, pixmap);
}
What I am looking for is a way similar to how QFont with drawText works. Regardless on how large my scale is, when I draw fonts it always looks sharp and I cannot detect individual pixels.
I imagine that I could tell QPainter to paint my icon into a given pixel rectangle, and QPainter transforms the rectangle itself before letting my QIconEngine::paint render the item into a possibly larger rectangle or pixmap. But I see no way how I could do something like this.
Am I just being stupid and not seeing the obvious solution?
I was indeed completely dump. I can just use QIcon::paint and pass it the rectangle. It will correctly delegate the request to the icon engine.
I do this by creating my icons/images as SVG files, and using QSvgRenderer to paint them onto a QPainter. The required classes are in the SVG module.
I created a very simple GUI that has a push button and a "Graphics View" widget from Display Widgets. On pushing the button I want a line to be drawn across the "Graphics View" widget. I have changed the name of the "Graphics View" widget to gv by right-clicking the widget in design view and then selecting change objectName. I am not able to understand how should the line be drawn. I read various texts on Qt that provided information about QPainter, PaintEvent etc. But I got more confused.
Kindly help me with this. A small sample code shall be really helpful for me as I am new to Qt.
A QGraphicsView is meant for displaying instances of QGraphicsItem that are managed by a component called QGraphicsScene. In your case, you'd create a QGraphicsLineItem and add it to the scene, or directly create it as an item of the scene by calling the addLine member function of your QGraphicsScene instance.
All drawing will be done by Qt itself, assuming that you did connect your graphics view and scene properly. Be sure to read The Graphics View Framework, which gives you an overview over how these components work.
You will find code examples of how to manage and display a scene using the graphics view framework here: http://doc.trolltech.com/4.6/examples-graphicsview.html
You can paint into a QPainter
Either override the paintevent and draw there
void MyDisplayWidget::paintEvent(QPaintEvent*)
{
QPainter p(this);
p.setPen(Qt::green);
p.drawText(10,10,"hello");
}
Or draw into a QImage and display that
QImage image = QImage(size);
QPainter p(&image);
p.drawText(10,10,"hello");
// draw or save QImage
You can even use the same draw function taking a QPainter * to draw either direct to the screen or to an image.
first you must knew some information about QPainter to have benefit of it.
QPainter provides highly optimized functions to do most of the drawing GUI programs require. It can draw everything from simple graphical primitives (represented by the QPoint, QLine, QRect, QRegion and QPolygon classes) to complex shapes like vector paths .and we use it to draw on paint devices
then render it to view,and we have alot of qpaint devices like : QWidget, QImage, QPixmap, QPicture, QPrinter, and QOpenGLPaintDevice you can use any one of them depending on your requirements then create QGraphic scene and add you paint device as qgraphic scene item to be shown in qgraphic view.
here is simple code:
Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
scene=new QGraphicsScene(this); //allocate your scene to your main widget
view=new QGraphicsView(scene,this);//here is your view
pixmap=new QPixmap(QSize(700,700));// paint device
view->resize(700,700);
}
Widget::~Widget()
{
delete ui;
}
void Widget::paintEvent(QPaintEvent *e)
{
painter=new QPainter;// create your painter
painter->begin(pixmap);//add painter to your paint device
painter->fillRect(0,0,300,300,Qt::red);//draw rect
painter->setPen(Qt::yellow);
painter->drawLine(0,0,700,700);//draw line
painter->end();
scene->addPixmap(*pixmap);// add your paint device to your scene
view->show();//then show your view
}
I've figured out how to use QPainter to draw rectangles. Now I want to have a drawing area where if the user clicks, a 1x1 rectangle is drawn where the mouse pointer is. To accomplish this, I assume I need a transparent Qt widget that supports the clicked() signal.
How do I make such a transparent widget? Or is there something else I can use? Perhaps I can only use the window's clicked() signal?
You don't really need a transparent widget?
All you have to do is implement
protected:
void mousePressEvent(QMouseEvent *event);
for your widget and draw your rectangle.
Take a look at scribble example that comes with Qt.