How to get the row/column location of a widget in a QGridLayout? - qt

Question

I made an own GridPushButton class to store the buttons position in gridlayout. The parent is QPushButton. I have a problem with asking it's x and y coordinates in window (like x:654, y:768). I thought it will be inherited from base class, but it doesn't. Now i have two options:
Use the original QPushButton class and somehow get its position in gridlayout (like x:0, y:1 if it's in the first row and second column) or
Use my GridPushButton and somehow get the x and y coordinate in window.
class GridPushButton : public QPushButton
{
Q_OBJECT
public:
GridPushButton(int coordX, int coordY, QWidget *parent = 0);
int coordinateX() { return _coordX; }
int coordinateY() { return _coordY; }
protected:
int _coordX;
int _coordY;
};
This is my class. I tried to make a new private variable and give it the QPushButton::x(), but doesn't work. Any idea to get the x and y coordinate from parent?
Or any idea to get the QPushButtons position in GridLayout?

Answer 1

There are two notions of coordinates that you're mixing up. There is the position within the parent widget. That's available via QWidget::x(), QWidget::y() and QWidget::pos() methods. You don't need to implement anything here: it already works.
Then there's the notion of the row and column within the grid layout. This can be obtained without a need for any subclassing. The grid layout knows where its widgets are, you can simply ask it for the row/column location of any widget.
#include <QtWidgets>
struct Pos { int row = -1, col = -1; };
Pos gridPosition(QWidget * widget) {
if (! widget->parentWidget()) return {};
auto layout = qobject_cast<QGridLayout*>(widget->parentWidget()->layout());
if (! layout) return {};
int index = layout->indexOf(widget);
Q_ASSERT(index >= 0);
int _;
Pos pos;
layout->getItemPosition(index, &pos.row, &pos.col, &_, &_);
return pos;
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QWidget w;
QGridLayout l(&w);
QLabel gridPos;
l.addWidget(&gridPos, 0, 0, 1, 4);
for (int i = 1; i < 4; ++ i)
for (int j = 0; j < 3; ++ j) {
auto b = new QPushButton(QString("%1,%2").arg(i).arg(j));
l.addWidget(b, i, j);
QObject::connect(b, &QPushButton::clicked, [&gridPos, b]{
auto p = gridPosition(b);
gridPos.setText(QString("Grid Pos: %1,%2")
.arg(p.row).arg(p.col));
});
}
w.show();
return a.exec();
}