Qt widget com problem - qt

I have a Rectangle widget, and a resize box widget, and a text edit widget. How can I compose them without using layouts ? I want all of them as a single widget.

The documentation for how to do a manual layout is in Qt Layout Management here.
Are you sure you can't use one of the standard layouts? You can make a custom widget with three children positioned inside using a layout (or layouts) and your new custom widget will still be just a single widget.

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Why won't QGroupBox widgets dynamically resize with rest of window?

I have a QMainWindow with the widgets laid out in a grid. They all resize proportionally when the window resizes as expected, except for the widgets placed inside a QGroupBox. The QGroupBox itself resizes, but the widgets inside just stay on the same place. If I apply a lay out on the QGroupBox, the widgets loose their original positions. Note that I'm using the .ui file with PyQt4. You can get the file here.
And this is what happens:
From Qt documentation on QGroupBox:
QGroupBox doesn't automatically lay out the child widgets (which are
often QCheckBoxes or QRadioButtons but can be any widgets).
There is an example showing how to setup a layout for a QGroupBox (which is the same a setting up a layout for any QWidget based object meant to store other objects, like QFrame for instance).
You must create a layout, call QGroupBox::setLayout and then add widgets to the layout. If you use QtCreator, right-click the QGroupBox and select the layout you want to use for it from the context menu.

Qt designer: How to add widget to a layout in the designer when the layout appears infinitely thin?

I am using Qt Designer, and I would like to move a couple of top-level widgets into a horizontal layout.
I have dragged a "Horizontal Layout" object into the form. I am now attempting to drag the desired widgets into the layout.
Unfortunately, the new Horizontal Layout widget is infinitely thin:
... and I cannot drag my "Import Progress" label widget or my progress bar widget into the new horizontal layout widget.
Note that when I attempt to drag the desired widgets over the new horizontal layout widget, Qt Designer does not do anything useful for me in terms of expanding the drop region to make the horizontal widget available as a drop target. So I'm stuck.
How do I add widgets to an infinitely-thin layout widget in Qt Designer?
Select the layout, and then drop the widget onto the corresponding selected item in the Object Inspector pane. If you find it tricky to select the layout on the actual form, you can also select it via the Object Inspector pane.
One way (that I usually do as a workaround for not having to show the structure panel) is to select the layout, setting the top or bottom margins to any value (10, whatever) and then dragging the component into the layout. Yeah, that is just for the pure pleasure of dropping the component in the layout, i know, but is a way.
My small trick:
Select layout
Change temporary "layoutTopMargin"
Drop into layout required widgets
Restore layoutTopMargin to default 0

How to make a layout invisible in Qt?

I add a layout in a dialog and sometimes I want it and all its containing widgets to hide. How to implement it? I try layout->setEnable(false), but it doesn't seem to work in my tests.
You can't do that. You should add a widget in your form, put children inside the widget and assign desired layout to the widget. The behavior will be generally the same, but you can use setVisible or hide methods of the widget.
Transform QLayout to QWidget first, then you can use QWidget->hide().

Setting QWidget to maximize within parent in Qt Creator/Designer?

I have dragged and dropped a widget within a parent widget in the designer within qt creator.
It has an arbitrary fixed position rectangle within its parent.
I want to modify it such that it will conform to its parents dimensions. That is it should be "maximized" within its parent.
What button in the designer do I press to do this?
This is what layouts are for. See this for an explanation.
I'm not particularly familiar with Qt Designer, but the general process is to create a layout (QHBoxLayout would work for you) for the parent widget, and add the child widget to that layout.
Another thing to consider is that, in your case, you could simply set the child widget to be the central widget of the QMainWindow:
this->setCentralWidget(theMaximizedWidget);

QT: two layouts add the same widget

In Qt: I create a widget-ui class, and I want to make the widget appear in two different layouts in two separate base widget(or window). So I want to:
widget_based_class* inside = new widget_based_class(base_widget1);
QHBoxLayout *lay1=new QHBoxLayout(base_widget1);
base_widget->setLayout(lay1);
lay1->addWidget(inside);
base_widget1.show();
-------------------------------
base_widget1.hide();
QHBoxLayout *lay2=new QHBoxLayout(base_widget2);
base_widget->setLayout(lay2);
lay2->addWidget(inside);
base_widget2.show();
How cound I achieve this? (My program is more complicated, and I didn't see the code work.)
Tank you.
A QWidget has only one parent widget and only one geometry (position and size) in that parent. Every call of QLayout::addWidget() will reparent that widget to the widget, the layout is installed on.
Your second call of setLayout won't work as expected, because you have to delete the the existing layout manager before setting the new one:
delete base_widget->layout();
base_widget->setLayout(lay2);
If base_widget hasn't already got a layout manager, the layout manager lay2 would simply be reparented.
If the widget will never be displayed twice on the screen, I don't see why you can't reparent it by addWidget/removeWidget.
In the OP, the parent widget/window is always hidden before the other one is shown. addWidget is called on the fly. We should also call removeWidget on the fly. It should be possible to move the widget around.
widget_based_class* inside = new widget_based_class(base_widget1);
QHBoxLayout *lay1=new QHBoxLayout(base_widget1);
base_widget->setLayout(lay1);
lay2->removeWidget(inside); // remove widget from other layout
lay1->addWidget(inside); // add widget to this layout
base_widget1.show();
-------------------------------
base_widget1.hide();
QHBoxLayout *lay2=new QHBoxLayout(base_widget2);
base_widget->setLayout(lay2);
lay1->removeWidget(inside); //remove widget from other layout
lay2->addWidget(inside); // add widget to this layout
base_widget2.show();
Make one widget and use a pointer in each layout?

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