Layering components with QT

Question

I am using QT Creator to develop a small GUI app. I have a GraphicsView component which spans the entire window. My question is, how can I place other widgets (such as transparent buttons) ontop of it in each of the four corners of the application. Also, how can I make sure that the lower right hand components get resized properly so that they stay in the lower right hand corner.

Answer 1

Ok, you can add a layout and QWidgets to a QGraphicsView so that they overlay the view underneath. You can't do this with QtDesigner (and I'm assuming QtCreator as well), so you'll have to do it in code. You can put the following code in the constructor of your window containing the QGraphicsView (named view) and it will add two buttons to a layout that will keep them anchored at the bottom right of the view:

QGridLayout *gridLayout;
QSpacerItem *horizontalSpacer;
QSpacerItem *verticalSpacer;
QPushButton *button1;
QPushButton *button2;

gridLayout = new QGridLayout(view);
horizontalSpacer = new QSpacerItem(0, 0, QSizePolicy::Expanding, QSizePolicy::Minimum);
verticalSpacer = new QSpacerItem(0, 0, QSizePolicy::Minimum, QSizePolicy::Expanding);
button1 = new QPushButton(view);
button1->setText("Button1");
button2 = new QPushButton(view);
button2->setText("Button2");

gridLayout->addWidget(button1, 1, 1, 1, 1);
gridLayout->addWidget(button2, 1, 2, 1, 1);
gridLayout->addItem(horizontalSpacer, 1, 0, 1, 1);
gridLayout->addItem(verticalSpacer, 0, 2, 1, 1);

It shouldn't be too much trouble to add two more buttons and two more spacers to achieve a button in each corner of the window.

Making standard QWidget controls transparent can be a bit tricky, especially buttons. Labels are easy though. You can refer to my answer to another question here for some hints for making transparent QPushButtons.