I amk new to qt. I tried to create a window with a widget. The widget contains a picture(a chess board). Now, If I tried to show the window it is showing a part of that picture. Here the code
#include<QApplication>
#include<QMainWindow>
#include<QWidget>
#include<QMenu>
#include<QMenuBar>
#include<QPainter>
#include<QFrame>
#include<QHBoxLayout>
#include<iostream>
using namespace std;
class MyWindow:public QMainWindow
{
public:
MyWindow();
};
class MyWidget:public QWidget
{
public:
MyWidget();
void paintEvent(QPaintEvent * event);
};
int main(int argc,char *argv[])
{
Q_INIT_RESOURCE(puzzle);
QApplication app(argc,argv);
MyWindow mainWindow;
mainWindow.show();
return app.exec();
}
MyWindow::MyWindow():QMainWindow()
{
setSizePolicy(QSizePolicy(QSizePolicy::Fixed,QSizePolicy::Fixed));
QMenu * fileMenu=menuBar()->addMenu(QObject::tr("Options"));
QAction * restartAction = fileMenu->addAction(tr("NewGame"));
QAction * exitAction = fileMenu->addAction(tr("Exit"));
exitAction->setShortcuts(QKeySequence::Quit);
QWidget * tempWidget=new MyWidget();
QFrame * newFrame=new QFrame();
QHBoxLayout * horizontal= new QHBoxLayout(newFrame);
horizontal->addWidget(tempWidget);
setCentralWidget(newFrame);
}
MyWidget::MyWidget():QWidget()
{
setMinimumSize(100,100);
setMaximumSize(1000,1000);
}
void MyWidget::paintEvent(QPaintEvent * event)
{
QPainter painter;
painter.begin(this);
painter.drawPixmap(QRect(0,0,500,600),QPixmap("Board").scaled(QSize(500,600),Qt::KeepAspectRatioByExpanding,Qt::SmoothTransformation));
painter.end();
}
In you paintEvent you are forcing the image to be painted to 500x600 pixels but you are not giving a fix size to the widget. So if the widget is smaller than that you cannot see the full image. If you do a setFixedSize(500, 600) it should fix your problem.
You are also doing
setSizePolicy(QSizePolicy(QSizePolicy::Fixed,QSizePolicy::Fixed));
in the main window. Are you giving a fix size apart from setting the size policy? If size policy is fixed you should specify a size for the window.
Also I think you can call setSizePolicy(QSizePolicy::Fixed); directly.
Related
I have a WidgetA widget, which is an owner-drawn widget. It's currently placed in QMainWindow's QVBoxLayout. After clicking a button, I'd like to "detach" WidgetA from this QVBoxLayout, insert QSplitter into this QVBoxLayout and "readd" WidgetA to this QSplitter. All this without destroying WidgetA, so it will preserve its drawing context, etc.
So, currently I have this (only one widget in a window):
I'd like to put a QSplitter between WidgetA and QMainWindow, and create a new widget, WidgetB, so I'd end up with:
Later I'd like it to split even further, so both WidgetA and WidgetB would still allow themselves to be detached and placed in a new QSplitter, so it would be possible to create f.e. this hierarchy:
And, to be complete, one more step:
I'm not very experienced in Qt, so what I'm trying to do may seem pretty obvious, but I couldn't find how to "reparent" widgets. Is this possible in Qt?
Please, see reparent example, may be it helps you:
//MyMainWindow.h
#include <QWidget>
#include <QPainter>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QSplitter>
class MyWidget: public QWidget
{
public:
MyWidget(QWidget* parent, int number)
: QWidget(parent),
m_number(number)
{
}
private:
virtual void paintEvent(QPaintEvent* e)
{
QWidget::paintEvent(e);
QPainter p(this);
p.fillRect( rect(), Qt::red);
p.drawText( rect(), Qt::AlignCenter, QString::number(m_number) );
}
private:
int m_number;
};
class MyMainWindow: public QWidget
{
Q_OBJECT
public:
MyMainWindow()
{
setFixedSize(300, 200);
m_mainLayout = new QVBoxLayout(this);
QHBoxLayout* buttonLayout = new QHBoxLayout;
m_mainLayout->addLayout(buttonLayout);
m_button = new QPushButton("Button", this);
buttonLayout->addWidget(m_button);
connect(m_button, SIGNAL(clicked()), this, SLOT(onButtonClickedOnce()));
m_initWidget = new MyWidget(this, 1);
m_mainLayout->addWidget(m_initWidget);
}
private slots:
void onButtonClickedOnce()
{
m_button->disconnect(this);
m_mainLayout->removeWidget(m_initWidget);
QSplitter* splitter = new QSplitter(Qt::Horizontal, this);
m_mainLayout->addWidget(splitter);
splitter->addWidget(m_initWidget);
MyWidget* newWidget = new MyWidget(splitter, 2);
splitter->addWidget(newWidget);
}
private:
QVBoxLayout* m_mainLayout;
QWidget* m_initWidget;
QPushButton* m_button;
};
//main.cpp
#include <QtWidgets/QApplication>
#include "MyMainWindow.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyMainWindow mainWindow;
mainWindow.show();
return a.exec();
}
When you operate with widget which is part of layout, then you need to use appropriate methods of QLayout (parent of QVBoxLayout) to detach the item from layout:
QLayout::removeWidget (removeItem if it is not widget, but spacer item or another layout)
QLayout::addWidget (addItem --/--)
Btw: even when widget moves between layouts, its parent may even stay same. I guess you have no need to call QWidget::setParent() as the calls of addWidget/removeWidget will do all work for you.
I have subclassed QWidget as follows:
class myClass : public QWidget
{
public:
explicit myClass(QWidget *parent);
protected:
void paintEvent(QPaintEvent *event);
}
myWidget::myWidget(QWidget* parent) : QWidget(parent)
{
setGeometry(10,10,100,100);
}
void myWidget::paintEvent(QPaintEvent *event)
{
QPainter qp(this);
QBrush bBlue(QColor::blue);
qp.fillRect(geometry(), bBlue);
}
What I wanted was to create a blue background QWidget placed onto the QWidget parent at 10,10 of size 100,100.
What I'm getting is a default size for myWidget of something like 100,50 at 0,0 with a black background (or transparent) and a blue rectangle starting at 10,10 within myWidget and clipped by myWidget.
It's like the setGeometry moved a rectangle within myWidget, not the myWidget itself.
Fairly new to Qt and would love an explanation and fix of above...
Thank you in advance.
Gary.
...here is actual code:
this is myWidget
class piTemplateWidget : public QWidget
{
public:
explicit piTemplateWidget(QWidget* parent);
static QColor* white;
static QColor* black;
static QColor* lightGrey;
static QColor* lightGreen;
piTemplate* tplt;
protected:
void paintEvent(QPaintEvent *event);
};
QColor* piTemplateWidget::white = new QColor(15,15,15);
QColor* piTemplateWidget::black = new QColor(250,250,250);
QColor* piTemplateWidget::lightGrey = new QColor(100,100,100);
QColor* piTemplateWidget::lightGreen = new QColor(250,15,250);
piTemplateWidget::piTemplateWidget(QWidget* parent) : QWidget(parent)
{
tplt = NULL;
move(100,100);
resize(300,240);
}
void piTemplateWidget::paintEvent(QPaintEvent *event)
{
QPainter qp(this);
QBrush bWhite(*white);
qp.fillRect(this->geometry(), bWhite);
// if (tplt==NULL)
// return;
// tplt->render(&qp);
}
...and this is the parent widgets constructor which instantiates my widget
piTemplateEdit::piTemplateEdit(QWidget *parent) :
QWidget(parent),
ui(new Ui::piTemplateEdit)
{
ui->setupUi(this);
currentTemplate = NULL;
if (piTemplate::templates->count()>0)
{
currentTemplate = (piTemplate*)piTemplate::templates->atIndex(0);
}
templateWidget = new piTemplateWidget(this);
templateWidget->tplt = currentTemplate;
}
...I hopes this helps.
Thank you.
Setting the geometry during the constructor may get overridden by the show event that the parent widget calls on it.
A common main function can look like this:
#include <QtGui/QApplication>
#include "mainwindow.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
// w.showMaxmized(); // This line would trump the "setGeometry() call
// in the constructor
return a.exec();
}
The geometry rect stored in a QWidget is described here:
http://qt-project.org/doc/qt-4.8/application-windows.html
http://qt-project.org/doc/qt-4.8/qwidget.html#pos-prop
I would not use this internal QWidget setting as how you fill your widget. If you do want to store some setting, make a QRect member variable and use that instead.
If you want to fill the entire box of your QWidget with a color you should try something like this:
void myWidget::paintEvent(QPaintEvent *event)
{
QPainter qp(this);
QBrush bBlue(QColor::blue);
qp.fillRect(QRect(0,0, this->width(), this->height()), bBlue);
}
Inside paint functions, they are relative to paintable area you are in.
http://qt-project.org/doc/qt-4.8/qwidget.html#mapTo
And like #LaszloPapp was saying, you need to use resize() and move(). And it wouldn't hurt to throw in a update() call after either one of those.
Also be sure to check out the show() method and all of its "See Also" items.
http://qt-project.org/doc/qt-4.8/qwidget.html#show
http://qt-project.org/doc/qt-4.8/qshowevent.html
If you #include <QShowEvent>, and call resize() when the show event happens, you may be good to go. If you are nesting this widget inside another widget you should look into using the size hint and setFixedSize or using Layouts properly.
http://qt-project.org/doc/qt-4.8/layout.html
Hope that helps.
I have a class in Qt that inherits QDockWidget. And that class contains another widget.
Is there any possibility to define a function in my QDockWidget inherited class that draws stuff on top of the contained widget? Like the painting to be independent of the contained widget but to be linked to the inherited class.
Thank you
Sure it's possible. It is fairly simple to do, in fact. You need to place a child widget that sits on top of everything else in your QDockWidget. To do it so, it must be the last child widget you add to your dockwidget. That widget must not to draw its background, and it can then draw over any children of the dockwidget. The widget's size must track the size of the parent widget.
Below is a self-contained example.
// https://github.com/KubaO/stackoverflown/tree/master/questions/overlay-line-11034838
#include <QtGui>
#if QT_VERSION > QT_VERSION_CHECK(5,0,0)
#include <QtWidgets>
#endif
class Line : public QWidget {
protected:
void paintEvent(QPaintEvent *) override {
QPainter p(this);
p.setRenderHint(QPainter::Antialiasing);
p.drawLine(rect().topLeft(), rect().bottomRight());
}
public:
explicit Line(QWidget *parent = nullptr) : QWidget(parent) {
setAttribute(Qt::WA_TransparentForMouseEvents);
}
};
class Window : public QWidget {
QHBoxLayout layout{this};
QPushButton left{"Left"};
QLabel right{"Right"};
Line line{this};
protected:
void resizeEvent(QResizeEvent *) override {
line.resize(size());
}
public:
explicit Window(QWidget *parent = nullptr) : QWidget(parent) {
layout.addWidget(&left);
right.setFrameStyle(QFrame::Box | QFrame::Raised);
layout.addWidget(&right);
line.raise();
}
};
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
Window w;
w.show();
return app.exec();
}
AFAIK: No.
Widgets are drawn in depth order, so whatever your QDockWidget derived class paints, will be drawn over by the contained widgets when they are updated (immediately afterwards no doubt, because paint updates are propagated to child widgets).
Python version for the accepted answer:
# Created by BaiJiFeiLong#gmail.com at 2022/1/15 10:22
from PySide2 import QtWidgets, QtGui, QtCore
app = QtWidgets.QApplication()
widget = QtWidgets.QWidget()
line = QtWidgets.QFrame(widget)
line.paintEvent = lambda _: QtGui.QPainter(line).drawLine(line.rect().topLeft(), line.rect().bottomRight())
line.setAttribute(QtCore.Qt.WidgetAttribute.WA_TransparentForMouseEvents)
widget.setLayout(QtWidgets.QGridLayout(widget))
widget.layout().addWidget(QtWidgets.QPushButton("CLICK ME", widget))
widget.resizeEvent = lambda event: line.resize(event.size())
line.raise_()
widget.show()
app.exec_()
Note that this will not work for QSplitter, in this condition, you should use QMainWindow as parent widget.
I'm having a Qt application with a main window that has five buttons aligned in a vertical order.
They all have the same size.
All I want to do is to increase the font size of the button label when the app goes fullscreen.
I would really appreciate a solution that does not need too much code ... was hoping that this was something that could be done in Qt Designer, but I couldn't find a way how to.
Any suggestions?
Best,
guitarflow
I can't think of any way to do it in designer, but it's really not too much code. Here's a quick-and-dirty proof of concept. You'd want to take into account margins (using QStyle::pixelMetrics and the like), but you get the idea.
#include <QtGui>
class FontAdjustingButton : public QPushButton {
public:
explicit FontAdjustingButton(QWidget *parent = NULL) : QPushButton(parent) {
setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
}
protected:
void resizeEvent(QResizeEvent *event) {
int button_margin = style()->pixelMetric(QStyle::PM_ButtonMargin);
QFont f = font();
f.setPixelSize(event->size().height() - button_margin * 2);
setFont(f);
}
};
int main(int argc, char **argv) {
QApplication app(argc, argv);
QWidget w;
QVBoxLayout *layout = new QVBoxLayout;
for (int i = 0; i < 5; ++i) {
FontAdjustingButton *btn = new FontAdjustingButton;
btn->setText(QString("Hello, world %1").arg(i));
layout->addWidget(btn);
}
w.setLayout(layout);
w.show();
return app.exec();
}
I need to create an alpha transparent widget, it's basically a navigation bar with a shadow and the widgets below need to be partially visible through the shadow. The widget loads a PNG then draws it on the paint event. The problem is that the shadow is all black and is not alpha-transparent.
This is the code I'm currently using:
NavigationBar::NavigationBar(QWidget *parent) : XQWidget(parent) {
backgroundPixmap_ = new QPixmap();
backgroundPixmap_->load(FilePaths::skinFile("NavigationBarBackground.png"), "png");
setAttribute(Qt::WA_NoBackground, true); // This is supposed to remove the background but there's still a (black) background
}
void NavigationBar::paintEvent(QPaintEvent* event) {
QWidget::paintEvent(event);
QPainter painter(this);
int x = 0;
while (x < width()) {
painter.drawPixmap(x, 0, backgroundPixmap_->width(), backgroundPixmap_->height(), *backgroundPixmap_);
x += backgroundPixmap_->width();
}
}
Does anybody know what I need to change to make sure the widget is really transparent?
You're doing too much work :-)
The setAttribute call is not necessary. By default, a widget will not draw anything on its background (assuming Qt >= 4.1). Calling QWidget::paintEvent is also unnecessary - you don't want it to do anything.
Rather than doing the pattern fill yourself, let Qt do it with a QBrush:
NavigationBar::NavigationBar(QWidget *parent) : XQWidget(parent) {
backgroundPixmap_ = new QPixmap();
backgroundPixmap_->load(FilePaths::skinFile("NavigationBarBackground.png"), "png");
// debug check here:
if (!backgroundPixmap_->hasAlphaChannel()) {
// won't work
}
}
void NavigationBar::paintEvent(QPaintEvent* event) {
QPainter painter(this);
painter.fillRect(0, 0, width(), height(), QBrush(*backgroundPixmap));
}
Adjust the height parameter if you don't want the pattern to repeat vertically.
Are you sure your PNG file is actually transparent? The following (which is essentially what you are doing) is working for me. If this fails on your machine, perhaps include what version of Qt you are using, and what platform.
#include <QtGui>
class TransparentWidget : public QWidget {
public:
TransparentWidget()
: QWidget(),
background_pixmap_(":/semi_transparent.png") {
setFixedSize(400, 100);
}
protected:
void paintEvent(QPaintEvent *) {
QPainter painter(this);
int x = 0;
while (x < width()) {
painter.drawPixmap(x, 0, background_pixmap_);
x += background_pixmap_.width();
}
}
private:
QPixmap background_pixmap_;
};
class ParentWidget : public QWidget {
public:
ParentWidget() : QWidget() {
QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(new TransparentWidget);
layout->addWidget(new QPushButton("Button"));
setLayout(layout);
setBackgroundRole(QPalette::Dark);
setAutoFillBackground(true);
}
};
int main(int argc, char **argv) {
QApplication app(argc, argv);
ParentWidget w;
w.show();
return app.exec();
}