#MOUSE COORDINATES IN QT HOW TO#

Now that you have some basic understanding of user input/output interaction, you can start doing some really fancy stuff. Now run it, and when you press the arrow keys on your keyboard, you will notice that you are moving the position where the mouse coordinates are being drawn to! Neat, huh? Painter.drawText(QRect(drawX + 20,drawY + 20,200,200), QString::number(mouseX) + ',' + QString::number(mouseY)) In the mainWindow constructor, add: tFocusPolicy(Qt::StrongFocus) //required for widget to accept keyboard eventsĪnd add custom event handler: void MainWindow::keyPressEvent(QKeyEvent *event)Īnd change your paintEvent function: void MainWindow::paintEvent(QPaintEvent *) In the mainWindow class file, add a new include reference to QKeyEvent: #include 'QKeyEvent' In the mainWindow header file, add a new symbol to override the default keyPressEvent: protected: In the mainWindow header file, add two new private variables: private: But, I’m making a game engine, so here’s how. Otherwise, usually, you won’t need to capture the keyboard events without creating more conflicts than necessary. Sometimes, you want to capture keyboard events, for example to implement controls for a game character. If you set it correctly, you will notice the relative mouse coordinates of the QWidget mainWindow being painted to itself. Void MainWindow::paintEvent(QPaintEvent *) This.update() //add the instruction to repaint the widget to a list of paint instructions Void MainWindow::mouseMoveEvent(QMouseEvent *event) always initialize your custom variables Ui->centralWidget->setMouseTracking(true) //have to set both ways in order to work properly, dont know why This->setMouseTracking(true) //this is required to read mouseMoveEvent xy-position Then, in the mainWindow class file (.cpp), make the following changes: #include 'QPainter' In the mainWindow header (.h), make the following changes: private: To determine the current mouse coordinates in your QWidget, you first need to override the default mouseMoveEvent.

#MOUSE COORDINATES IN QT HOW TO#

Possible usage for this is to create a point-and-click game or to determine hotspots in your own custom QWidget.īefore we get into any coding, please look at my Hello World Tutorial which shows you how to setup the minimum mainWindow widget. By overriding any of these protected functions, you can customize how the QWidget operates.įor example, you might want to determine what the mouse coordinates are within your QWidget. QWidget has the following protected functions keyPressEvent, keyReleaseEvent, mousePressEvent, mouseMoveEvent, mouseReleaseEvent, paintEvent. The most common aspects of GUI interaction you might want to take over are mouse, keyboard, or painting events. One way is to override QWidget’s default events. But when you want to implement something that is really unique, then you’ll have to be able to engage the internal processes that make your user-friendly interactions so intuitive. They may provide very specific features and might suit your needs perfectly.

The point remains the same during the entire process of drawing a line.For the most part, Qt comes with a bunch of convenience widgets built on top of their own QWidget. We will store this point in QPointF origPos. In mousePressEvent() the user specifies the starting point of the line. How to override QGraphicsScene::mousePressEvent(), mouseMoveEvent() and mouseReleaseEvent() Void makeItemsControllable(bool areControllable) Void mouseReleaseEvent(QGraphicsSceneMouseEvent *event)

Void mouseMoveEvent(QGraphicsSceneMouseEvent *event) Void mousePressEvent(QGraphicsSceneMouseEvent *event) We also override keyPressEvent() in order to delete selected items with the Delete key.Įnum Mode Apart from overriding event handlers, we also introduce a helper function makeItemsControllable(bool) that adapts the selectability and mobility of items depending on the scene mode. introduce a slot actionGroupClicked(QAction*) that switches between scene modesīelow you can see how to subclass QGraphicsScene.introduce 2 QActions - lineAction and selectAction, as well as QActionGroup that ensures exclusivity of these two actions.introduce enum Mode to distinguish between the drawing and selection mode.introduce QPointF origPos that stores the starting position of the currently drawn item.introduce QGraphicsLineItem* itemToDraw which stores the address of the currently drawn item.override mousePressEvent(), mouseMoveEvent() and mouseReleaseEvent().

To obtain the desired functionality we need to subclass QGraphicsScene and QMainWindow. This is demonstrated on an example that has two operation modes, namely drawing and selection mode. This article shows how to draw a QGraphicsLineItem with mouse coordinates during run time. UserDrawing/userdrawing.pro (Qt 5 compatible)

Mouse coordinates in qt