I'm new to Qt, so I wonder whether there is a way to set the size of a QMainWindow to (for example) 70% of the user's desktop.I tried the stretch factor but it didn't work. QWidget::setFixedSize worked but only with a pixel number, I think.
Somewhere in your QMainWindow constructor, do this:
resize(QDesktopWidget().availableGeometry(this).size() * 0.7);
This will resize the window to 70% of the available screen space.
Thanks to Amir eas. The problem is solved. Here's the code for it:
#include <QDesktopWidget>
#include <QMainWindow>
...
QDesktopWidget dw;
MainWindow w;
...
int x=dw.width()*0.7;
int y=dw.height()*0.7;
w.setFixedSize(x,y);
You can use the availableGeometry(QWidget*) method in QDesktopWidget, this will give you the geometry of the screen that this widget is currently on. For example:
QRect screenSize = desktop.availableGeometry(this);
this->setFixedSize(QSize(screenSize.width * 0.7f, screenSize.height * 0.7f));
Where this is the MainWindow pointer.
This will work when using multiple screens.
Just to update #muesli's answer for Qt6, QDesktopWidget had been deprecated in Qt5 and in Qt6 is removed.
The new equivalent code is
resize(QGuiApplication::primaryScreen()->availableGeometry().size() * 0.7);
Related
On Windows ,I am trying to create Qt application with transparent DOCKWIDGETS, where background of dock widget is transparent when it is floated. So we can see through dock widget.
Currently it looks black as below.
Code as below
QDockWidget * dock3 = new QDockWidget(tr("DOCK3 TranslucentBackground"),
textEdit,Qt::FramelessWindowHint);
dock3->setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea);
//dock3->setWindowFlags(dock2->windowFlags()|Qt::FramelessWindowHint);
dock3->setAttribute(Qt::WA_TranslucentBackground);
//dock3->setAttribute(Qt::WA_NoSystemBackground);
{
QWidget* WindowRect = new QWidget(dock3);
QWidget* titleRect = new QLabel ("Title",WindowRect);
titleRect->setFixedSize(QSize(30,60));
titleRect->setStyleSheet("background:rgb(0,0,255);");
QWidget* ContentRect = new QLabel("Content",WindowRect);
ContentRect->setFixedSize(QSize(60,30));
ContentRect->setStyleSheet("background:rgb(0,255,0);");
QVBoxLayout* layout = new QVBoxLayout(WindowRect);
layout->addWidget(titleRect);
layout->addWidget(ContentRect);
dock3->setWidget(WindowRect);
}
One way is to use setWindowOpacity(qreal) of the QDockWidget.
But keep in mind that this will apply the opacity to all children of the QDockWidget.
For reference: https://doc.qt.io/qt-5/qwidget.html#windowOpacity-prop
Another way is to use style sheets:
setStyleSheet("background-color: transparent;");. Unfortunately this doesn't work for top level widgets until you set the attribute WA_TranslucentBackground of the base widget.
For reference:
https://doc.qt.io/qt-5/stylesheet.html
https://doc.qt.io/qt-5/qwidget.html#styleSheet-prop
Try with this article:
Qt tip & Trick: Masking Widgets
You can do it with:
setStyleSheet("background-color: rgba(0,0,0,0)");
You can try to to it in the drawin customisation by changing the style of your widget like:
MyCustomWidget {background-color: none;}
It should work
I understand that you want to see through the docking bar only when it is floating. When it's not (docked), it makes no sense because there's nothing behind to be shown.
Using setAttribute(Qt::WA_TranslucentBackground) does the trick. I'm under Linux, hopefully, it also works for Windows (I found some posts where people additionally set setAttribute(Qt::WA_NoSystemBackground), it made no difference for me under Linux, if Qt::WA_TranslucentBackground is not enough for you, give it a try with both).
#include <QMainWindow>
#include <QApplication>
#include <QDockWidget>
#include <QLabel>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow w;
w.setCentralWidget( new QWidget() );
w.centralWidget()->setStyleSheet("background-color: green");
QDockWidget* dock = new QDockWidget();
dock->setWidget( new QLabel("Hello World",dock) );
// make docking bar transparent!
dock->setAttribute(Qt::WA_TranslucentBackground);
w.addDockWidget(Qt::BottomDockWidgetArea,dock, Qt::Horizontal);
w.show();
return a.exec();
}
When docked, it looks like this:
When floating, it looks like this:
You can see the central widget (green), can be visible through the docking bar.
Reference: Make QWidget transparent
The following code (Qt 5, same behaviour with Qt 4.8) uses a QGridLayout to add widgets above and to the left of a QScrollArea (to serve as a kind of header later):
#include <QApplication>
#include <QMainWindow>
#include <QGridLayout>
#include <QScrollArea>
class ColoredWidget : public QWidget {
public:
ColoredWidget(const QColor& color, QWidget* parent) : QWidget(parent) {
QPalette pal;
QBrush brush(color);
brush.setStyle(Qt::SolidPattern);
pal.setBrush(QPalette::Active, QPalette::Window, brush);
setPalette(pal);
setAutoFillBackground(true);
}
};
class MainWindow : public QMainWindow {
public:
MainWindow(QWidget* parent) : QMainWindow(parent) {
resize(300, 400);
QWidget* centralwidget = new ColoredWidget(QColor(0xff, 0xf0, 0xb5), this);
QGridLayout* layout = new QGridLayout();
centralwidget->setLayout(layout);
setCentralWidget(centralwidget);
// create widget with fixed height of 20 px and maximum width of 200
QWidget* topHeader = new ColoredWidget(Qt::green, centralwidget);
topHeader->setMaximumWidth(200);
topHeader->setFixedHeight(20);
// create widget with fixed width of 20 px and maximum height of 200
QWidget* leftHeader = new ColoredWidget(Qt::blue, centralwidget);
leftHeader->setFixedWidth(20);
leftHeader->setMaximumHeight(200);
// create scroll area as main widget
QWidget* view = new QScrollArea();
layout->addWidget(topHeader, 0, 1);
layout->addWidget(leftHeader, 1, 0);
// layout->addWidget(leftHeader, 1, 0, Qt::AlignTop); // widget not displayed at all!
layout->addWidget(view, 1, 1);
}
};
int main(int argc, char ** argv) {
QApplication app( argc, argv );
MainWindow win(0);
win.show();
return app.exec();
}
The QGridLayout documentation says that "Columns and rows behave identically", thus I would expect that the two widgets are layouted the same way.
However, the left one is automatically vertically centered, while the top widget is aligned to the left within the cell (and not centered horizontally). I would like to have the left widget also at a fixed position, means aligned to the top:
Which property causes this different behaviour between the two widgets, one beeing centered, the other being at a fixed position?
How can I influence the alignment (I can probably add a flexible spacer to fix it, but ideally I would like to avoid that)? I tried with Qt::AlignTop, but that made the blue widget disappear.
Althought this question is pretty old, I will add my answer for all those that come here afterwards, like me.
Setting the alignment either with
layout->setAlignment(leftHeader, Qt::AlignHCenter | Qt::AlignTop);
or with
layout->addWidget(leftHeader, 1, 0, Qt::AlignTop);
is intuitiv and seems to be the right way. If it is setup completly it is also working as expected.
But why does the Widget vanish then?
Long story short: because leftHeader has a size of 0.
In my pretty similar situation I've setfixedHeight() and the widget reappeared, this should also work by setting a value for minimalHeight() for example.
Long Story - Details
I've put myself in position of gridLayout and tried to determine the size of leftHeader:
Outside of the layout leftHeader got a fixed width of 20 - ok, but no given height. With the defaults of QWidget this leads to a default-height of 0.
Documentation of void QGridLayout::addWidget() and void QGridLayout::addLayout() states:
... The alignment is specified by alignment. The default alignment is
0, which means that the widget fills the entire cell. ...
source
Hence for default alignment of 0 the height of leftHeader is obviously set as height of its row.
But in case a different Qt::Alignment is used, as in the question (Qt::AlignTop ), it is not that simple.
From my point of view the layout is unable to determine the correct height without further settings from the designer.
Having a quick look at the implementation of void QGridLayout::addWidget(), we can detect that a QLayoutItem(as part of QGridBox) is created inside the QGridLayout for each added widget resp. Layout.
So it seems that the QGridLayout relies on default layout mechanisms of Qt based on the settings from the added widget/Layout (like minSize, maxSize, BaseSize, Size Increment, etc ).
In combination with 1.) this implies a height of 0 for leftHeader and therefore nothing to draw resp. it seems that the widget has vanished.
Although not a minimal solution you could probably fix the alignments by adding a QHBoxLayout in the cell for the green widget and a QVBoxLayout in the cell for the blue widget. Add the green widget to the QHBoxLayout and the blue widget to the QVBoxLayout. Then apply addStretch(n) to both the QHBoxLayout and QVBoxLayout. Maybe this is what you already mentioned you could do and then we are at the same level of knowledge concerning this. I believe this is the way I have solved these kind of issues and I haven't spent more time on it.
Try this:
setAlignment(Qt::AlignHCenter | Qt::AlignTop );
I've got a window full of QPushButtons and QLabels and various other fun QWidgets, all layed out dynamically using various QLayout objects... and what I'd like to do is occasionally make some of those widgets become invisible. That is, the invisible widgets would still take up their normal space in the window's layout, but they wouldn't be rendered: instead, the user would just see the window's background color in the widget's rectangle/area.
hide() and/or setVisible(false) won't do the trick because they cause the widget to be removed from the layout entirely, allowing other widgets to expand to take up the "newly available" space; an effect that I want to avoid.
I suppose I could make a subclass of every QWidget type that override paintEvent() (and mousePressEvent() and etc) to be a no-op (when appropriate), but I'd prefer a solution that doesn't require me to create three dozen different QWidget subclasses.
This problem was solved in Qt 5.2. The cute solution is:
QSizePolicy sp_retain = widget->sizePolicy();
sp_retain.setRetainSizeWhenHidden(true);
widget->setSizePolicy(sp_retain);
http://doc.qt.io/qt-5/qsizepolicy.html#setRetainSizeWhenHidden
The only decent way I know of is to attach an event filter to the widget, and filter out repaint events. It will work no matter how complex the widget is - it can have child widgets.
Below is a complete stand-alone example. It comes with some caveats, though, and would need further development to make it complete. Only the paint event is overridden, thus you can still interact with the widget, you just won't see any effects.
Mouse clicks, mouse enter/leave events, focus events, etc. will still get to the widget. If the widget depends on certain things being done upon an a repaint, perhaps due to an update() triggered upon those events, there may be trouble.
At a minimum you'd need a case statement to block more events -- say mouse move and click events. Handling focus is a concern: you'd need to move focus over to the next widget in the chain should the widget be hidden while it's focused, and whenever it'd reacquire focus.
The mouse tracking poses some concerns too, you'd want to pretend that the widget lost mouse tracking if it was tracking before. Properly emulating this would require some research, I don't know off the top of my head what is the exact mouse tracking event protocol that Qt presents to the widgets.
//main.cpp
#include <QEvent>
#include <QPaintEvent>
#include <QWidget>
#include <QLabel>
#include <QPushButton>
#include <QGridLayout>
#include <QDialogButtonBox>
#include <QApplication>
class Hider : public QObject
{
Q_OBJECT
public:
Hider(QObject * parent = 0) : QObject(parent) {}
bool eventFilter(QObject *, QEvent * ev) {
return ev->type() == QEvent::Paint;
}
void hide(QWidget * w) {
w->installEventFilter(this);
w->update();
}
void unhide(QWidget * w) {
w->removeEventFilter(this);
w->update();
}
Q_SLOT void hideWidget()
{
QObject * s = sender();
if (s->isWidgetType()) { hide(qobject_cast<QWidget*>(s)); }
}
};
class Window : public QWidget
{
Q_OBJECT
Hider m_hider;
QDialogButtonBox m_buttons;
QWidget * m_widget;
Q_SLOT void on_hide_clicked() { m_hider.hide(m_widget); }
Q_SLOT void on_show_clicked() { m_hider.unhide(m_widget); }
public:
Window() {
QGridLayout * lt = new QGridLayout(this);
lt->addWidget(new QLabel("label1"), 0, 0);
lt->addWidget(m_widget = new QLabel("hiding label2"), 0, 1);
lt->addWidget(new QLabel("label3"), 0, 2);
lt->addWidget(&m_buttons, 1, 0, 1, 3);
QWidget * b;
b = m_buttons.addButton("&Hide", QDialogButtonBox::ActionRole);
b->setObjectName("hide");
b = m_buttons.addButton("&Show", QDialogButtonBox::ActionRole);
b->setObjectName("show");
b = m_buttons.addButton("Hide &Self", QDialogButtonBox::ActionRole);
connect(b, SIGNAL(clicked()), &m_hider, SLOT(hideWidget()));
QMetaObject::connectSlotsByName(this);
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Window w;
w.show();
return a.exec();
}
#include "main.moc"
You can use a QStackedWidget. Put your button on the first page, a blank QWidget on the second, and change the page index to make your button vanish while retaining its original space.
I've 3 solutions in my mind:
1) Subclass your QWidget and use a special/own setVisible() replacement method witch turns on/off the painting of the widget (if the widget should be invisible simply ignore the painting with an overridden paintEvent() method). This is a dirty solution, don't use it if you can do it other ways.
2) Use a QSpacerItem as a placeholder and set it's visibility to the opposite of the QWidget you want to hide but preserve it's position+size in the layout.
3) You can use a special container widget (inherit from QWidget) which gets/synchronizes it's size based on it's child/children widgets' size.
I had a similar problem and I ended up putting a spacer next to my control with a size of 0 in the dimension I cared about and an Expanding sizeType. Then I marked the control itself with an Expanding sizeType and set its stretch to 1. That way, when it's visible it takes priority over the spacer, but when it's invisible the spacer expands to fill the space normally occupied by the control.
May be QWidget::setWindowOpacity(0.0) is what you want? But this method doesn't work everywhere.
One option is to implement a new subclass of QWidgetItem that always returns false for QLayoutItem::isEmpty. I suspect that will work due to Qt's QLayout example subclass documentation:
We ignore QLayoutItem::isEmpty(); this means that the layout will treat hidden widgets as visible.
However, you may find that adding items to your layout is a little annoying that way. In particular, I'm not sure you can easily specify layouts in UI files if you were to do it that way.
Here's a PyQt version of the C++ Hider class from Kuba Ober's answer.
class Hider(QObject):
"""
Hides a widget by blocking its paint event. This is useful if a
widget is in a layout that you do not want to change when the
widget is hidden.
"""
def __init__(self, parent=None):
super(Hider, self).__init__(parent)
def eventFilter(self, obj, ev):
return ev.type() == QEvent.Paint
def hide(self, widget):
widget.installEventFilter(self)
widget.update()
def unhide(self, widget):
widget.removeEventFilter(self)
widget.update()
def hideWidget(self, sender):
if sender.isWidgetType():
self.hide(sender)
I believe you could use a QFrame as a wrapper. Although there might be a better idea.
Try void QWidget::erase (). It works on Qt 3.
I'm building an Qt-Application without the default window border as a frameless window.
The window functions are included by setting window flags in the QMainWindow like:
MainDialog::MainDialog(QWidget *parent):
QMainWindow(parent), currentProject(NULL), currentUser(NULL),
aViews(new QList<AViewForm*>()),
bViews(new QList<BViewForm*>()),
cViews(new QList<CViewForm*>())
{
ui.setupUi(this);
this->statusBar()->showMessage(tr(""));
this->setWindowFlags(Qt::Window | Qt::FramelessWindowHint | Qt::WindowMinimizeButtonHint | Qt::WindowMaximizeButtonHint | Qt::WindowSystemMenuHint);
...
}
The MainWindow has an .ui file within, thats why I cannot inherit from QDesktopWidget.
The Problem I have now is that the Appication overlays the windows taskbar when maximizing.
My Question now: is there any posibility to find out the available height of the OS desktop without the
availableGeometry().height()
-Method of QDesktopWidget? I cannot find anything in the documentation :(
Somebody else here asked a similar Question but used a QWidget instead of a QMainWindow.
I would be glad about any hints to my Problem
As you say you can use QDesktopWidget. If you don't have your class inherit from it you can create one in your constructor just for retrieving the height :
QDesktopWidget w;
int availableHeight = w.availableGeometry().height();
Guess thats not good practise, but i solved it as followed:
I built a new class which needs a MainWindow as param and with slots for the scaling actions:
FullScreen::FullScreen(QMainWindow &mainWindow, QObject *parent) : QObject(parent), mainWindow(mainWindow)
{
this->saveCurrentPosition();
}
void FullScreen::maximize()
{
this->saveCurrentPosition();
mainWindow.move(QApplication::desktop()->mapToGlobal(QApplication::desktop()->availableGeometry().topLeft()));
mainWindow.resize(QApplication::desktop()->availableGeometry().size());
}
void FullScreen::normalize()
{
mainWindow.move(lastGlobalPosition);
mainWindow.resize(lastSize);
}
void FullScreen::saveCurrentPosition()
{
lastGlobalPosition = mainWindow.mapToGlobal(mainWindow.rect().topLeft());
lastSize = mainWindow.size();
}
The only Problem which now occures is when the application is fullscreen and you move the taskbar. I have not set any resizeEvent though
Seems to be possible with native controls (see here and here) so now I'm looking for some Qt code to do it.
I use this code for the second display in full screen successfully on both Windows & Linux
QRect screenres = QApplication::desktop()->screenGeometry(1/*screenNumber*/);
SecondDisplay secondDisplay = new SecondDisplay(); // Use your QWidget
secondDisplay->move(QPoint(screenres.x(), screenres.y()));
secondDisplay->resize(screenres.width(), screenres.height());
secondDisplay->showFullScreen();
One way of doing it in Qt5 is to use QWindow::setScreen to set the screen on which the window should be shown. QWidget has a windowHandle() that returns the pointer to the QWindow.
Here is how to show your widget on second screen in full-screen mode :
QWidget * widget = new QWidget();
widget->show();
widget->windowHandle()->setScreen(qApp->screens()[1]);
widget->showFullScreen();
My take on this:
auto const desktop(QApplication::desktop());
setGeometry(desktop->screenGeometry(1));
#ifndef Q_OS_WIN
setWindowState(Qt::WindowState(Qt::WindowFullScreen | windowState()));
#endif // Q_OS_WIN
showFullScreen first, then setGeometry.
Qt5 tested OK
This problem got solved while using window->showFullScreen() instead of window->show().