I have a Qt Widget which has a frame, containg the rest of the widgets.
I only want one of the widgets to expand on maximazing the window, so I've set a max value for the others.
But it will only expand if I set a grid layout to the frame, which messes up the place of the widgets.
How can I solve it?
Do you use any kind of layout ?
Size policy only works if the parent has a layout set.
You can use a combination of different layouts to obtain the desired look, otherwise you will have to calculate the size of the 'expanding widget' yourself in the resize event method of the parent.
Related
When I run my program it will display all content properly, and when I resizing the main window, the layout along with all associated widgets remain fixed, rather than resizing with the main window. I used to increase my all widget and listWidget respect to window computer resolution size but still this not one work properly.
I used this one code finding the system height and width.
QWidget widget;
widget.resize(widget.width(), widget.minimumHeight());
QRect rec = QApplication::desktop()->screenGeometry();
int h = rec.height();
int w = rec.width();
// Increasing the listwidget size
ui->listWidget->setFixedHeight(h);
ui->listWidget->setFixedWidth(w);
//increasing the button size
ui->pushButton->setFixedHeight(h0.2);
ui->pushButton->setFixedWidth(w0.2);
At this link you will find two screenshots that illustrate my problem.
Please resolve to solve my problem. Thanks very much in advance.
When defining the layout of your windows and forms in Qt Designer you have to define each element of your form in advance, in order to have a working layout.
This solution is based on the screenshots provided in the comments to the question. Follow these steps:
Add an empty widget to the central area of your form, if there is nothing there. It will be used as a placeholder for the controls you will add later, and of course you can replace it with whatever widget you want. But you need it there to define a proper layout.
In the property panel, set the horizontal QSizePolicy of this widget to MinimumExpanding.
Add an horizontal spacer to the left side of your progress bar.
Define a minimum/maximum width for the white widget on the left (I guess it's a text area). As an example set the maximum width to 200
pixels.
Make the same for the QTabWidget on the right.
Give a minimum height to the Groupbox on top.
Then give the grid layout to the MainWindow.
You should get something similar in the designer view (I use a dark theme, yours will have different colors of course):
If you complete all steps you should have a nicely resizing window.
For the future: remember to integrally define your layouts, also using placeholder widgets when needed, read carefully the documentation about the widgets size policies (there are several, you need to play with them to fully understand each one) and keep in mind that Qt uses a container based approach which is different, as an example from those used by the .Net framework that relies on the concept of anchors.
EDIT : to answer questions in the comments
You will need to add a layout to any widget that contains other widgets, e.g. adding controls to your groupbox will require to give it a grid, horizontal or vertical layout in order to scale nicely on resize. Again use spacers and size policies to make it look the way you want. If you need to add or remove controls, or change their positions, you may need to brake the layout, rearrange and then set it again.
You can also select groups of widgets and give them a layout e.g. vertical, than another group and set them horizontal and so on... then give a grid layout to the container widget to build a compound layout.
There are endless possibilities, you just need to practice and go through trial and error as for everything else...
You can also do it all programmatically, check the Qt widgets documentation for this. But for complex layouts I would not go that way: it's a lot of code... and you have to compile and run to test every modification.
Using the QtCreator, within the designer you can simply right-click on the parent-widget and add a Grid-Layout.
This one resizes it's children to it's dimensions.
When I maximize my window, I want to restrict a vertical layout (and the entire row below it also) so that it has a specific size (lets say a width of 200). How can I achieve this? Below is what I get now. The buttons are stretched too far. I want them to keep a width of 200.
To stop the buttons stretching, use the following steps in Qt Designer:
click on scrollArea in the Object Inspector
click on Break Layout on the toolbar
click on scrollArea in the Object Inspector
click on Lay Out in a Grid on the toolbar
click on scrollAreaWidgetContents in the Object Inspector
scroll down to the bottom of the Property Editor
change layoutColumnStretch to 0,1
These steps should remove an empty column from the scroll-area grid-layout, and make the second column stretch to take up the available space when the window is resized.
You just need to restrict the maximum width of all widgets (in this case the buttons) within the layouts of this grid column to the expected size, else they'll just keep expanding. You may also have to fiddle the horizontal size policy; I seem to remember that buttons were a bit tricky in this regard (or was that the height?), but can't test it right now.
The layout size contraint you tried only applies to the layout's direct parent widget, if it has one, which isn't the case for the vertical layouts here.
I have been now two years working deeply with Qt layout system. After this time i encountered thosand of problems with SizePolicies and Layouts. I normally found out solutions, but never really understood what i was doing.
Now i was taking some time to try to understand correctly and build a 101 GUIDE for them and never fail. I found out this piece of information in the documentation about QSizePolicy of a QWidget:
This property holds the default layout behavior of the widget
If there is a QLayout that manages this widget's children, the size
policy specified by that layout is used. If there is no such QLayout,
the result of this function is used.
I thought that if you had a QLabel, for example, and you set the policies to Horizontal Expanding, Vertical Fixed, THE LABEL itself changed that way.
But it doesn't, at all.
When reading that i see that it talks about ITS CHILDREN inside the LAYOUT. So what does it mean, then?. Nothing is inside the label, is that why it does not work?.
WHat about inserting a label inside a QFrame, and telling the frame to be Expanding... Will the QFrame expand or stretch (depending on the rest of brother widgets in the same Layout) or will the label expand or stretch, not the QFrame?
What a mess...
What about Stretching?. If you set stretching 10 when you add the widget:
layout->addwidget(label, 10, Qt::AlignHCenter);
It doesn't work either.
Stretch 0 when you add the widget means : Take the policies i told you. Default, depends on the type of widget. Button-like widgets have expanding-fixed. Box-like Expanding-Expanding...
Stretch 10 means: grow maximum.
Am i right? Well. When having a QFrame and a QLabel inside, setting Expanding, and 10 to strech to the label DOES NOT WORK.
I don't understand all of your questions, so I will only answer to those that I think i do.
I thought that if you had a QLabel, for example, and you set the policies to Horizontal Expanding, Vertical Fixed, THE LABEL itself
changed that way. But it doesn't, at all.
I don't know what that means. What is the exact behavior you're expecting and what is actually happening? Is this label in a layout? Are there any other widgets in this layout?
WHat about inserting a label inside a QFrame, and telling the frame to be Expanding...
If you set a QSizePolicy to your QFrame object and set a layout to it, this size policy might be ignored. Docs: If there is a QLayout that manages this widget's children, the size policy specified by that layout is used. If there is no such QLayout, the result of this function is used. This means that the widget's layout should manage the size of the widget. Note that it will still respect the minimum/maximum width/height values.
Stretch 10 means: grow maximum.
What makes you think that?. The stretch factor is dependent on other widgets inside the layout. Docs: Stretch factors are used to change how much space widgets are given in proportion to one another.
When having a QFrame and a QLabel inside, setting Expanding, and 10 to strech to the label DOES NOT WORK.
Does not work how? If you set stretch for QFrame to 1 and for QLabel to 10, your QLabel object should always be 10 times as wide/high(depending of your layout type) as your QFrame object. If your QFrame has a layout and it contains children, then this might not work as it would depend on the childrens size policies.
I have a widget which I'm putting in a QVBoxLayout. This widget's layout is a QVBoxLayout which includes a QTableWidget. When I display this everything is fine but the QTableWidget only shows a few rows. How can I set the height of the table to a decent value (like 20 rows) while still allowing the table to resize?
I've tried calling table.setMinimumHeight(200) but then the table can NEVER be smaller than 200. I've also tried setting the container widget height using setMinimumHeight but this has the same problem.
Check the sizePolicy for the QTableWidget. This will have horizontal and vertical size policies which, if I understand you correctly, should be set to "expanding" or "minimum expanding". There are a number of options and combinations for these and sometimes it can be tricky getting the right combination for all the widgets in your layout to get what you are looking for.
The size policies will work in combination with your min/max height/width settings and those of the other widgets in the layout.
For those of you who haven't been reading my Qt questoins, I am learning Qt for a project. I have only limited experience with GUI design at all, and not in Qt.
I've got a horizontal layout that I want to populate with some buttons. I can feed these buttons in just fine, but my formerly-square buttons are stretched horizontally to take up more space.
I want to let the layout manager determine the best way to size these buttons, but I also want their original proportions to remain intact. For instance, if I start would with 32X32 buttons that need to shrink to fit all of them in the layout, I want them to shrink proportionally so that the width to height scale is maintained. 20X20, 16X16, 12X12 would all be just fine, but 24X16 would be an example of dimensions that are unacceptable.
I've tinkered with size policies on the buttons and stretch options. I'm not seeing, even after reading the QPushButton and QHboxLayout classes how to do this. How is it accomplished?
Thanks.
As long as I understand the question correctly, I think what you want is QBoxLayout::addStretch(). This will add a spacer object that fills the unused space. So the buttons will have their ideal size and the spacer will fill the rest. You can try experimenting with this in Designer, it's easier than the write/compile/run cycle.
You should take a look at the answers to this question. This is a recap of my answer there.
You need to create a custom derivative of QLayoutItem, which overrides bool hasHeightForWidth() and int heightForWidth( int width ) to preserve the aspect ratio. You could either pass the button in and query it, or you could just set the ratio directly. You'll also need to make sure the widget() function returns a pointer to the proper button.
Once that is done, you can add a layout item to a layout in the same manner you would a widget. So when your button gets added, change it to use your custom layout item class.
I haven't actually tested any of this, so it is a theoretical solution at this point. I don't know of any way to do this solution through designer, if that was desired.