I want to know the size of a certain QGraphicsView. Its size isn't fixed because the widget is part of a grid layout. I tried using this->ui->myGraphicsView->width() and its height equivalent but these values aren't accurate.
How can I get the current size of a QGraphicsView?
Constantly received 100x30 as the size of my QGraphicsView as well. It turned out I was asking for the size of the QGraphicsView before it was shown.
After moving my initialization code to showEvent, I got the correct dimensions.
If you wanna know the actual size of QGraphicsView, QGraphicsView::size();
If you wanna konw only the content size of QGraphicsView, QGraphisView::viewport().size();
retrieve the width/height in MainWindow's constructor
That is the problem! The widget isn't painted already and you're asking for it's size. Use other events like event, showEvent, paintEvent to get the right size within the initialization process of a widget.
Answer:
After calling MainWindow::show(), then get the size.
Description:
I had the same problem as Pieter. In the widget constructor like MainWindow::MainWindow() you can't get the correct size of the widget like QGraphicsView in Grid Layout because in that constructor the widget's size and location are not determined. Therefore, in MainWindow::MainWindow() you have to call show() and then get the size of the view or other widget.
I have the same problem with you. QGraphicsView.size() is always return (100,30). I have solved this problem in my project.
Check below code is like this
...in a QTabWidget class...
def addANewTab(self):
view = QGraphicsView()
...set view param...
index = self.addTab(view, 'test')
view.size() # it will return (100,30)
self.setCurrentIndex(index)
view.size() # it will return correct size
so like Bigbell Mercy answered , you show make sure QGraphicsView is show!
Related
I use QSplitter to place some widgets side by side.
Being a user, I can resize those widgets just dragging a splitter.
Being a programmer, I don't know how to specify exactly what width and what height do I want at the moment.
That's my original state (adjusted by different stretches).
I tried to use setFixedSize(), but after that call the user can't resize widgets by itself anymore (and that's definitely correct behavior, because the size gets 'fixed').
If I use resize(), it has almost no effect. The widget is resized, but (!) incorrectly and (!) when I start dragging again the widget gets its initial state.
Is there any way to resize that left widget in code correctly? I don't want to have fixed size but resize() doesn't work properly, as you can see. So what should I do?
QSplitter hast its method QSplitter::setSizes(QList<int>) where each entry in the list is the size of the widget in pixels, from left to right or top to bottom respectively. The method does not require you to know the exact width, it still works with guessed sizes.
I use this functionality for instance to store the user defined sizes (obtained by QSplitter::sizes()) in a QSettings instance on the program shutdown and reapply them when the software is started again. If they are not set for some reason I just set the overall width divided by the number of widgets in the splitter and it works fine enough as an initial state.
Is there a way to define an initial size for a child window widget (inherited from QMdiSubWindow)? I don't want to necessary limit the minimum size or prevent it from being resized, but just to show the window at the first time with a given size.
I've tried to reimplement sizeHint and to define different size policies, but even with those changes the autoAjust call seem to make the window very small (size 200 x 200) when it is first displayed. The window contains a widget with this hierarchy: QVBoxLayout -> QScrollArea -> QLabel. The QLabel is used to show an image with the size 512 x 512.
EDIT: Correct the class to QMdiSubWindow.
you can use resize(int w, int h).
It will not set the maximum and minimum size.
It will just change the initial size of the child window.
Well actually, what it really does is: it changes the "current" size of the child window. But the first current size is the "initial" size. So basically its the same.
To my knowledge, there's no such thing in Qt as a QSubWindow.
However, a call to setGeometry on a QWidget will set its size.
After much searching for an answer, and experimenting, I found this to work for me.
child->parentWidget()->resize(900, 700);
child->parentWidget()->updateGeometry();
child->show();
// child->showMaximized();
You can use showMaximized() in place of show() and the (900, 700) will still be used if the window is later changed to normal.
Ok, so I'd like to display an image with qt where the image resizes with the browser and maintains the aspect ratio while also remaining centered in the window. I can get the resizing with aspect ratio to work correctly, but when I align it with Qt::AlignCenter, the qwidget no longer resizes (remains a fixed size). So basically, I can get either option to work but not together.
A good example of what I'm trying to do would be the imshow() function in matlab. This resizes the image while maintaining the aspect ratio and also centering the image in the window. The code I have is soemthing like this:
void roilayout::resizeEvent(QResizeEvent *event)
{
QSize p(roiview->refimage->size());
p.scale(roiview->view->size(), Qt::KeepAspectRatio);
roiview->view->resize(p);
}
and in the constructor:
roiview = new roiwindow;
roiview->view->setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
roiview->view->setCursor(Qt::CrossCursor);
roiview->view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
roiview->view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
QHBoxLayout *layoutContainer = new QHBoxLayout;
layoutContainer->addWidget(roiview->view);
setLayout(layoutContainer);
I searched google and couldnt find anything. Also asked a similar question a little while back but from the answers it appears I didn't ask the question clearly enough. Thanks.
A couple of things: First it would be helpful to know what type of control "view" is.
Also, I don't think you should need to resize the child control "view" (whatever type it is) within the parent's resizeEvent() callback.
A better solution might be to set the sizeHint policy on the child widget to automatically expand.
The child-parent hierarchy is the following: mainWindow -> centralWidget -> frame -> widget.
Widget is being resized during the application lifetime, however it is always set to a fixed size. I want the QMainWindow to resize based on that - to have a minimum size that is needed to display all the widgets.
To do that I currently have to do this.
widget->setFixedSize(x, y);
frame->setFixedSize(frame->sizeHint());
centralWidget->setFixedSize(centralWidget->sizeHint());
mainWindow->setFixedSize(mainWindow->sizeHint());
It doesn't work properly if I only resize the main window. All parents of widget need to be resized in order for this to work. Is there a more elegant way? Is it possible to make the main window call resize on all of it's children?
NOTE: All widgets except 'widget' have automatic layout management. So I find it strange that they don't resize themselves based on 'widget'.
It is the job of the layout to determine the size and position of the widgets. So if you explicitly resize a child widget which is inside a layout, you need to ensure that the new size is passed correctly through the layout system. This can be done by ensuring that the widget’s sizeHint() returns the new size. The value returned by the sizeHint() will be used when the layout calculates the new size. So after the sizeHint() has changed, simply call updateGeometry() [qt.nokia.com] that will notify the layout system that the widget has changed and may need to change geometry.
An alternative way to ensure that the parent widget is resized in response to its child being resized, is to call setFixedSize() on the child.
For more details check this...
http://qt-project.org/faq/answer/how_can_i_trigger_the_parent_widget_to_resize_when_its_child_widget_is_resi
You should let layout manage widgets size. As far as i am concerned there is 2 situations:
With layout when you are resizing a parent all children are resizing too regarding the size policy you provided to them. If you choose a fixed policy children will not be resized. So you have to resize them by hand... but it's quit weird.
When you are resizing a child like you are doing, parent is not automatically resized. You need to do it by hand. Fortunately there's a "magic function for that: AdjustSize. If you call it from QMainWindow all widget will be resized to their optimize size. It is possible (I can't test it here) that this does not work at runtime if size policy is set to fixed.
Hope that helps
I know that this is a very specific C++ and Qt related question, but maybe someone can help me, anyway ...
See the code below: I want to display an image within a scroll area. The view port of the scroll area shall have a defined initial size. That means, if the image's size is bigger than the initial size of the view port, scroll bars will be visible, otherwise not.
// create label for displaying an image
QImage image( ":/test.png" );
QLabel *label = new QLabel( this );
label->setPixmap( image.toPixmap() );
// put label into scroll area
QScollArea *area = new QScrollArea( this );
area->setWidget( label );
// set the initial size of the view port
// NOTE: This is what I'd like to do, but this method does not exist :(
area->setViewPortSize( QSize( 300, 300 ) );
It shall be possible to resize the whole application so that the view port will get another size than the initial one.
Unfortunatelly I was not able to find out, how to set the size of the view port. Qt's layout mechanism seems to set a default size for the view port, but up to now I was not able to change it. Setting a new size with
area->setMinimumSize( QSize( 300, 300 ) );
will actually set the demanded size, but then the scroll area looses the ability to get resized to a size smaller than 300x300.
Any ideas?
I think that you are looking at the problem the wrong way. The QScrollArea is just a widget that you put in a frame or QMainWindow. The size of the widget is controlled by the layout of the widget that contains it.
Take a look at this example from Trolltech: Image Viewer Example
You can try:
class MyScrollArea : public QScrollArea
{
virtual QSize sizeHint() const { return QSize( 300, 300 ); }
};
// create label for displaying an image
QImage image( ":/test.png" );
Label *label = new QLabel;
label->setPixmap( image.toPixmap() );
// put label into scroll area
QScollArea *area = new MyScrollArea( this );
area->setWidget( label );
However layout and Qt is amazingly Voodoo. It is IMO its least functional part.
if that doesn't work, try calling QWidget::resize() on various widgets.
Is the scroll area the top level widget? If so, simply call
area->resize(300,300);
If it's inside a hierarchy you need to resize the toplevel appropriately (complex), or set the minimumSize of the area. You could also try to experiment with the LayoutPolicy - assuming the sizeHint is QSize(300,300) you can give it the appropriate size policy according to what's defined in https://doc.qt.io/qt-5/qsizepolicy.html#Policy-enum
I don't think you can do exactly that very easily, which is (if I'm reading correctly), size the widget so that the internal area is 300x300. You might be able to fudge it, however, since a scroll area is a type of frame, which inherits from QWidget. This means you could just call area->resize( 300 + fudge, 300 + fudge ), where your fudge values account for the extra bit taken up by the frame's drawing.
I'm not sure this would work in a dynamically resizable dialog, however. I haven't ever done anything quite like this.
If you're trying to display an image inside a scroll area, your best bet isn't going with a label.
You should try using a QGraphicsView/QGraphicsScene/QGraphicPixmapItem (instead of the Scroll Area and label). The performance is far better when displaying images. The scroll area and label will re-draw the image very poorly as you move around using the scroll bars.
For example, you have a ".ui" file with a QGraphicsView on the gui called "qgvImageView" and a QImage called "image"...
QGraphicsScene *scene = new QGraphicsScene(qgvImageView);
QPixmap pixTmp(QPixmap::fromImage(image));
QGraphicsPixmapItem * ppixItem = scene->addPixmap( pixTmp );
ppixItem->setPos(0,0);
Check out the QT Documentation. BTW: This was introduced in Qt 4.2
I'm not sure if this will specifically fix the problem, but there is a chance that the QGraphicsView will react better to what you're trying to do.
How about using
area->setGeometry(int x, int y, int w, int h);