I want to make my widget always have square size. Following this answer, I have overridden QWidget::heightForWidth(), and I also call setHeightForWidth(true) in the constructor, as suggested by #peppe. The size policy is set to Preferred,Preferred (for both horizontal size and vertical size).
However, heightForWidth() is not being called. Is there anything I am doing wrong?
This is the declaration of heightForWidth() in my Widget class:
virtual int heightForWidth(int) const;
This happens on Linux and Windows.
Your widget needs to be in a layout. The below works on both Qt 4 and 5.
In Qt 4, it will only force the toplevel window's minimum size if it's in a layout.
In Qt 5, it doesn't force the toplevel window size. There may be a flag for that or it's a bug but I don't recall at the moment.
#include <QApplication>
#include <QWidget>
#include <QPainter>
#include <QDebug>
#include <QVBoxLayout>
#include <QFrame>
class Widget : public QWidget {
mutable int m_ctr;
public:
Widget(QWidget *parent = 0) : QWidget(parent), m_ctr(0) {
QSizePolicy p(sizePolicy());
p.setHeightForWidth(true);
setSizePolicy(p);
}
int heightForWidth(int width) const {
m_ctr ++;
QApplication::postEvent(const_cast<Widget*>(this), new QEvent(QEvent::UpdateRequest));
return qMax(width*2, 100);
}
QSize sizeHint() const {
return QSize(300, heightForWidth(300));
}
void paintEvent(QPaintEvent *) {
QPainter p(this);
p.drawRect(rect().adjusted(0, 0, -1, -1));
p.drawText(rect(), QString("h4w called %1 times").arg(m_ctr));
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QWidget w;
QVBoxLayout * l = new QVBoxLayout(&w);
l->addWidget(new Widget);
QFrame * btm = new QFrame;
btm->setFrameShape(QFrame::Panel);
btm->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
l->addWidget(btm);
w.show();
return a.exec();
}
To stay square if the widget is in a layout you must reimplement
bool hasHeightForWidth() const{ return true; }
int heightForWidth(int w) const { return w; }
functions of the layout class.
Related
I am doing a qt project, my goal is to draw something based on my input. The signal is in the main, and the drawing is in another object, I am not able to connect them.
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
Frequency fre; //this is the class that does the drawing
QWidget *window = new QWidget;
QGridLayout *grid = new QGridLayout;
QGroupBox *groupBox = new QGroupBox(QObject::tr("Volume"));
QSpinBox *spinBox = new QSpinBox;
spinBox->setRange(0, 5);
QObject::connect(spinBox, SIGNAL(valueChanged(int)),&fre, SLOT(setVolume(int)));
QVBoxLayout *Vbox = new QVBoxLayout;
Vbox->addWidget(spinBox);
groupBox->setLayout(Vbox);
grid->addWidget(groupBox, 4,7,1,1);
window->setLayout(grid);
window->show();
return app.exec();
}
This is how I set up the Frequency class :
in h file
class Frequency : public QGLWidget
{
Q_OBJECT
public slots:
void setVolume(int value);
in cpp file
void Frequency :: setVolume(int val) {
vol = val;
updateGL();
}
void Frequency :: paintGL() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
draw();
}
Since I can't put all this in the comment section, I'm going to put it here:
I copied your code and I'm not able to reproduce the error with Qt version 5.14.0, because when I change the value in any way, the method, void MyObject::setVolume(int value) is being called.
This code should work for you. Possibly, you are running it in release mode, and used a breakpoint to check if it was called (which doesn't always work on release mode).
// #include "QtWidgetsApplication4.h"
#include <QtWidgets/QApplication>
#include "MyObject.h"
#include <QGridLayout>
#include <QGroupBox>
#include <QSpinBox>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
// QtWidgetsApplication4 w;
// w.show();
// return a.exec();
MyObject object;
QWidget* window = new QWidget;
QGridLayout* grid = new QGridLayout;
QGroupBox* groupBox = new QGroupBox(QObject::tr("Volume"));
QSpinBox* spinBox = new QSpinBox;
spinBox->setRange(0, 5);
QObject::connect(spinBox, SIGNAL(valueChanged(int)), &object, SLOT(setVolume(int)));
QVBoxLayout* Vbox = new QVBoxLayout;
Vbox->addWidget(spinBox);
groupBox->setLayout(Vbox);
grid->addWidget(groupBox, 4, 7, 1, 1);
window->setLayout(grid);
window->show();
return a.exec();
}
#pragma once
#include <QObject>
class MyObject : public QObject
{
Q_OBJECT
public slots:
void setVolume(int value);
private:
int m_volume;
};
#include "MyObject.h"
void MyObject::setVolume(int value)
{
m_volume = value;
}
I am trying to design something like a timeline view for my video player. I decided to use QTableWidget as the timeline since it suits my purpose. My widget looks like this:
I want the green line to run through the widget when i click on play. Here is my MVCE example:
//View.cpp
View::View(QWidget* parent) : QGraphicsView(parent)
{
QGraphicsScene* scene = new QGraphicsScene(this);
TableWidget* wgt = new TableWidget;
scene->addWidget(wgt);
QGraphicsLineItem* item = new QGraphicsLineItem(30, 12, 30, wgt->height() - 9);
item->setPen(QPen(QBrush(Qt::green), 3));
item->setFlags(QGraphicsItem::ItemIsMovable);
scene->addItem(item);
setScene(scene);
}
Here is TableWidget
TableWidget::TableWidget(QWidget* parent) : QTableWidget(parent)
{
setColumnCount(10);
setRowCount(10);
//Hides the numbers on the left side of the table
verticalHeader()->hide();
//Prevents top header from highlighting on selection
horizontalHeader()->setHighlightSections(false);
//Makes the cells un-editable
setEditTriggers(QAbstractItemView::NoEditTriggers);
setSelectionMode(QAbstractItemView::MultiSelection);
}
Problem:
Moving the line item reflects changes to the scene it has been added to i.e. when i drag the line using mouse, the line moves in the scene but not inside the TableWidget.
What do i want
I want the green bar to act like a horizontal slider. It should go through the TableWidget horizontally making the widget scroll along with it showing the current position of the frame indicated by the numbers shown on the header.
Something like as shown below (notice the Red line):
I know this might not be the best way to implement a timeline but i would appreciate any other ideas to implement.
A possible solution is to overwrite the itemChange method to restrict movement as shown below:
#include <QApplication>
#include <QGraphicsRectItem>
#include <QGraphicsView>
#include <QTableWidget>
#include <QHeaderView>
#include <QGraphicsProxyWidget>
class SeekBarItem: public QGraphicsRectItem{
public:
SeekBarItem(QRectF rect, QGraphicsItem *parent=nullptr)
: QGraphicsRectItem(rect, parent)
{
setFlag(QGraphicsItem::ItemIsMovable, true);
setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);
setBrush(Qt::red);
}
protected:
QVariant itemChange(GraphicsItemChange change, const QVariant &value){
if(change == QGraphicsItem::ItemPositionChange){
QPointF p = value.toPointF();
qreal max = parentItem()->boundingRect().bottom()- boundingRect().bottom();
qreal min = parentItem()->boundingRect().top()-boundingRect().top();
if(p.y() > max) p.setY(max);
else if (p.y() < min) p.setY(min);
p.setX(pos().x());
return p;
}
return QGraphicsRectItem::itemChange(change, value);
}
};
class TableWidget: public QTableWidget
{
public:
TableWidget(QWidget* parent=nullptr) : QTableWidget(10, 10, parent)
{
verticalHeader()->hide();
horizontalHeader()->setHighlightSections(false);
setEditTriggers(QAbstractItemView::NoEditTriggers);
setSelectionMode(QAbstractItemView::MultiSelection);
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGraphicsView view;
QGraphicsScene *scene = new QGraphicsScene;
view.setScene(scene);
QGraphicsProxyWidget *proxy = scene->addWidget(new TableWidget);
QGraphicsRectItem *it = new QGraphicsRectItem(QRectF(0, 0, 10, proxy->boundingRect().height()), proxy);
it->setBrush(Qt::green);
SeekBarItem *seekBarItem = new SeekBarItem(QRectF(-5, 0, 20, 50));
seekBarItem->setParentItem(it);
view.resize(640, 480);
view.show();
return a.exec();
}
Update:
#include <QApplication>
#include <QGraphicsRectItem>
#include <QGraphicsView>
#include <QTableWidget>
#include <QHeaderView>
#include <QGraphicsProxyWidget>
#include <QScrollBar>
class TableWidget: public QTableWidget
{
public:
TableWidget(QWidget* parent=nullptr) : QTableWidget(10, 10, parent)
{
verticalHeader()->hide();
horizontalHeader()->setHighlightSections(false);
setEditTriggers(QAbstractItemView::NoEditTriggers);
setSelectionMode(QAbstractItemView::MultiSelection);
setHorizontalScrollMode(QAbstractItemView::ScrollPerPixel);
}
};
class SeekBarItem: public QGraphicsRectItem{
public:
SeekBarItem(int width, QAbstractItemView *view, QGraphicsScene *scene)
: QGraphicsRectItem(nullptr),
proxy(new QGraphicsProxyWidget()),
m_view(view)
{
proxy->setWidget(m_view);
scene->addItem(proxy);
setParentItem(proxy);
setFlag(QGraphicsItem::ItemIsMovable, true);
setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);
setBrush(Qt::red);
setRect(0, 0, width, m_view->height());
scrollbar = m_view->horizontalScrollBar();
}
protected:
QVariant itemChange(GraphicsItemChange change, const QVariant &value){
if(change == QGraphicsItem::ItemPositionChange){
QPointF p = value.toPointF();
qreal max = parentItem()->boundingRect().right()- boundingRect().right();
qreal min = parentItem()->boundingRect().left()-boundingRect().left();
if(p.x() > max) p.setX(max);
else if (p.x() < min) p.setX(min);
p.setY(pos().y());
float percentage = (p.x()-min)*1.0/(max-min);
int value = scrollbar->minimum() + percentage*(scrollbar->maximum() - scrollbar->minimum());
scrollbar->setValue(value);
return p;
}
return QGraphicsRectItem::itemChange(change, value);
}
private:
QGraphicsProxyWidget *proxy;
QAbstractItemView *m_view;
QScrollBar *scrollbar;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGraphicsView view;
QGraphicsScene *scene = new QGraphicsScene;
view.setScene(scene);
TableWidget *table = new TableWidget;
SeekBarItem *seekBarItem = new SeekBarItem(15, table, scene);
view.resize(640, 480);
view.show();
return a.exec();
}
I am learning Qt for fun. And I got a question:
How could I drag and drop the QLabel in Qt among two different windows?
Here is what I have so far:
As you can tell from the .gif(which does not want to become downloaded and visible here for some reasons, but if you click on the link to it, you can clearly see it) provided above right now there are two main problems:
I can not move the QLabel outside of the window (and hence am not able to register the drag and drop event).
The label is flashing for some reasons when I am moving it.
Here is the relevant part of the implementation from the .gif:
#ifndef DRAGGERP_H
#define DRAGGERP_H
#include <QLabel>
#include <QApplication>
#include <QMouseEvent>
#include <QPoint>
class DraggerP : public QLabel
{
QPoint offset;
QPoint startingPosition;
public:
DraggerP(QWidget* parent = nullptr) : QLabel(parent){ }
protected:
void enterEvent(QEvent* event) override
{
QApplication::setOverrideCursor(Qt::PointingHandCursor);
}
void leaveEvent(QEvent* event) override
{
QApplication::restoreOverrideCursor();
}
void mousePressEvent(QMouseEvent* event) override
{
startingPosition = pos();
offset = QPoint(
event->pos().x() - pos().x() + 0.5*width(),
event->pos().y() - pos().y() + 0.5*height()
);
}
void mouseMoveEvent(QMouseEvent* event) override
{
move(event->pos() + offset);
}
void mouseReleaseEvent(QMouseEvent* event) override
{
move(startingPosition);
}
};
#endif // DRAGGERP_H
This is the extension of the QLabel I am using to create the drag and drop effect.
I do not need the whole solution, at least an idea of how to accomplish this and what am I doing wrong here.
Here is a pretty good example and I used it as a starting point.
That strange movement that the QLabel suffers is because the position of the QLabel now depends on the layout, the job of the layout is to establish the position of the widgets depending on the policies you establish.
The solution is not to implement those actions in the QLabel but in the MainWindow as I show below:
#include <QApplication>
#include <QLabel>
#include <QMainWindow>
#include <QScrollArea>
#include <QVBoxLayout>
#include <QTime>
#include <QDrag>
#include <QMimeData>
#include <QMouseEvent>
class MainWindow: public QMainWindow {
QScrollArea scrollArea;
QWidget contentWidget;
QVBoxLayout lay;
public:
MainWindow(QWidget* parent=nullptr): QMainWindow(parent){
qsrand((uint) QTime::currentTime().msec());
setCentralWidget(&scrollArea);
scrollArea.setWidget(&contentWidget);
contentWidget.setLayout(&lay);
scrollArea.setWidgetResizable(true);
for(int i=0; i< 20; i++){
QLabel *label = new QLabel(QString("label %1").arg(i));
QPalette pal = label->palette();
pal.setColor(QPalette::Background, QColor(10 +qrand() % 240, 10 +qrand() % 240, 10 +qrand() % 240));
label->setAutoFillBackground(true);
label->setPalette(pal);
lay.addWidget(label);
}
setAcceptDrops(true);
}
protected:
void mousePressEvent(QMouseEvent *event){
QMainWindow::mousePressEvent(event);
QWidget *child = childAt(event->pos());
if(qobject_cast<QLabel *>(child))
createDrag(event->pos(), child);
}
void dropEvent(QDropEvent *event){
QByteArray byteArray = event->mimeData()->data("Label");
QWidget * widget = *reinterpret_cast<QWidget**>(byteArray.data());
QLabel * new_label = qobject_cast<QLabel *>(widget);
QWidget *current_children = childAt(event->pos());
QLabel * current_label = qobject_cast<QLabel*>(current_children);
int index = 0;
if(new_label){
if(current_label)
index = lay.indexOf(current_label);
else{
index = 0;
QLayoutItem *item = lay.itemAt(index);
while(item->widget()->pos().y() < event->pos().y() && item)
item = lay.itemAt(index++);
}
lay.insertWidget(index, new_label);
}
}
private:
void createDrag(const QPoint &pos, QWidget *widget){
if(widget == Q_NULLPTR)
return;
QByteArray byteArray(reinterpret_cast<char*>(&widget),sizeof(QWidget*));
QDrag *drag = new QDrag(this);
QMimeData * mimeData = new QMimeData;
mimeData->setData("Label",byteArray);
drag->setMimeData(mimeData);
QPoint globalPos = mapToGlobal(pos);
QPoint p = widget->mapFromGlobal(globalPos);
drag->setHotSpot(p);
drag->setPixmap(widget->grab());
drag->exec(Qt::CopyAction | Qt::MoveAction);
}
protected:
void dragEnterEvent(QDragEnterEvent *event){
if(event->mimeData()->hasFormat("Label"))
event->acceptProposedAction();
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w1;
MainWindow w2;
w1.show();
w2.show();
return a.exec();
}
I created my own font dialog from QFontDialog (new SLOT added). After that, I can't set icon (*.png) to my new font dialog (with func. setWindowIcon). If I use setWindowIcon to default QFontDialog - everything is OK. So, how to set icon to my new font dialog?
FontDialog.h
#include <QtGui>
#include <QtCore>
class FontDialog: public QFontDialog {
public:
FontDialog();
~FontDialog();
public slots:
void someSlot(void);
};
FontDialog.cpp
#include "FontDialog.h"
FontDialog::FontDialog() {
}
FontDialog::~FontDialog() {
}
void someSlot(void) {
}
main.cpp
#include "FontDialog.h"
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
FontDialog *fontDialog = new FontDialog();
fontDialog->setWindowIcon(QIcon(".//icon.png")); // !!!NOT WORKING!!! for custom QFontDialog
fontDialog->show();
app.exec();
}
I'm using Qt 4.8.5 with Qt Designer 2.7.1 environment.
Thanks for any help.
The below works under Qt 4.8.4 on both OS X and Windows 7. It also works on 5.1.1 on Windows, but not on OS X :(
#include <QFontDialog>
#include <QApplication>
#include <QIcon>
#include <QPainter>
class Dialog : public QFontDialog {
public:
Dialog(QWidget *parent = 0) : QFontDialog(parent) {}
Dialog(const QFont & initial, QWidget *parent = 0) : QFontDialog(initial, parent) {}
};
QIcon myIcon(const QColor & color)
{
QIcon icon;
QPixmap pm(128, 128);
pm.fill(Qt::transparent);
QPainter p(&pm);
p.translate(64, 64);
p.scale(50, 50);
p.setBrush(color);
p.setPen(QPen(Qt::lightGray, 0.1));
p.drawEllipse(-1, -1, 2, 2);
icon.addPixmap(pm);
return icon;
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
a.setWindowIcon(myIcon(Qt::red));
Dialog d;
d.setWindowIcon(myIcon(Qt::blue));
d.show();
return a.exec();
}
I am putting a QProgressBar inside a QSplashScreen by subclassing QSplashScreen. It overrides the drawContents() method.
I thought I had set the geometry correctly, but it renders at both the top and bottom of the screen. I don't know why. Perhaps there's another way to align it. The numbers are correct, as the image is 380x284, so a 19 height progress bar should be 265 pixels down.
Sorry for crappy picture, splash screen wasn't showing up with print screen button. It's just a 1 color white splash screen at the moment, but as you can see, progress bar at top and bottom (they're both the same colors, its the lighting from the camera).
http://i.imgur.com/p1LoJ.jpg
Another issue will be the showMessage() method of QSplashScreen. I want the message to appear above the progress bar, right-aligned... if anyone has any ideas how to do that.
splashscreen.cpp
#include "splashscreen.h"
SplashScreen::SplashScreen(QApplication *app, QWidget *parent) :
QSplashScreen(parent)
{
this->app = app;
this->setPixmap(QPixmap(":/images/splashscreen.png"));
this->setCursor(Qt::BusyCursor);
// if I dont make it a child, it *only* renders at the top
progress = new QProgressBar(this);
progress->setGeometry(0, 265, 380, 19); // puts it at bottom
progress->setAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
progress->setValue(0);
progress->setMaximum(100);
progress->setEnabled(true);
this->showMessage("Hello", Qt::AlignBottom);
connect(progress, SIGNAL(valueChanged(int)), this, SLOT(progressBarUpdated(int)));
}
void SplashScreen::drawContents(QPainter *painter)
{
QSplashScreen::drawContents(painter);
this->progress->render(painter);
}
void SplashScreen::progressBarUpdated(int value)
{
this->repaint();
this->app->processEvents();
}
splashscreen.h
#ifndef SPLASHSCREEN_H
#define SPLASHSCREEN_H
#include <QSplashScreen>
#include <QProgressBar>
#include <QApplication>
class SplashScreen : public QSplashScreen
{
Q_OBJECT
public:
explicit SplashScreen(QApplication *app, QWidget *parent = 0);
QProgressBar *progress;
QWidget *spacer;
QApplication *app;
public slots:
void progressBarUpdated(int value);
protected:
void drawContents(QPainter *painter);
};
#endif // SPLASHSCREEN_H
main.cpp
#include <QtGui/QApplication>
#include <time.h>
#include "splashscreen.h"
#include "mainwindow.h"
int main(int argc, char *argv[])
{
srand(time(0));
QApplication a(argc, argv);
SplashScreen *splash = new SplashScreen(&a);
splash->show();
// snip.. loading a ton of stuff into memory at startup
// if you're testing this you might have to sleep/timer here iono
MainWindow w;
splash->finish(&w);
w.show();
return app.exec();
}
You can paint progress directly, without creating QProgressBar. For example:
sp.h:
#ifndef SPLASHSCREEN_H
#define SPLASHSCREEN_H
#include <QSplashScreen>
#include <QApplication>
class SplashScreen : public QSplashScreen
{
Q_OBJECT
public:
explicit SplashScreen(QApplication *app, QWidget *parent = 0);
int m_progress;
QApplication *app;
public slots:
void setProgress(int value)
{
m_progress = value;
if (m_progress > 100)
m_progress = 100;
if (m_progress < 0)
m_progress = 0;
update();
}
protected:
void drawContents(QPainter *painter);
};
#endif // SPLASHSCREEN_H
sp.cpp
#include "sp.h"
SplashScreen::SplashScreen(QApplication *aApp, QWidget *parent) :
QSplashScreen(parent), app(aApp), m_progress(0)
{
this->setPixmap(QPixmap(":/images/splashscreen.png"));
this->setCursor(Qt::BusyCursor);
this->showMessage("Hello", Qt::AlignBottom);
}
void SplashScreen::drawContents(QPainter *painter)
{
QSplashScreen::drawContents(painter);
// Set style for progressbar...
QStyleOptionProgressBarV2 pbstyle;
pbstyle.initFrom(this);
pbstyle.state = QStyle::State_Enabled;
pbstyle.textVisible = false;
pbstyle.minimum = 0;
pbstyle.maximum = 100;
pbstyle.progress = m_progress;
pbstyle.invertedAppearance = false;
pbstyle.rect = QRect(0, 265, 380, 19); // Where is it.
// Draw it...
style()->drawControl(QStyle::CE_ProgressBar, &pbstyle, painter, this);
}
May be this helps you.