Qt Font Manipulation: Alternatives to a Missing Swap Function

1. Swapping Font Values
   

QFont font1("Arial", 12);
QFont font2("Times New Roman", 10);

// Swap font family
QString temp = font1.family();
font1.setFamily(font2.family());
font2.setFamily(temp);

// Similarly swap other properties like size, weight, etc.

1. Standard Template Library (STL) swap
   

Qt utilizes the C++ Standard Template Library (STL) for various functionalities. The STL provides a generic std::swap() function that can be used to swap the values of two variables of any type, including QFont. This approach is suitable if you're working with generic code and don't know the specific type of the objects being swapped.

QFont font1("Arial", 12);
QFont font2("Times New Roman", 10);

std::swap(font1, font2);

• For dynamic widget manipulation in Qt GUI, consider using techniques like storing widgets in containers (e.g., QList) and then hiding/showing them based on your needs.
• Qt provides a meta-object system that allows member functions like swap to be defined for custom classes. However, QFont doesn't have a built-in swap function.

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Swapping Font Properties

#include <QApplication>
#include <QLabel>

int main(int argc, char *argv[])
{
  QApplication app(argc, argv);

  // Create labels with different fonts
  QLabel label1("This is Arial!", QFont("Arial", 14));
  QLabel label2("This is Times New Roman!", QFont("Times New Roman", 16));

  label1.show();
  label2.show();

  // Swap font family and size between labels
  QString tempFamily = label1.font().family();
  int tempSize = label1.font().pointSize();

  label1.setFont(QFont(label2.font().family(), tempSize));
  label2.setFont(QFont(tempFamily, label2.font().pointSize()));

  return app.exec();
}

This code creates two labels with different fonts and then swaps their font families and sizes using temporary variables.

Using std::swap with QFont

#include <QApplication>
#include <QLabel>

int main(int argc, char *argv[])
{
  QApplication app(argc, argv);

  // Create labels with different fonts
  QLabel label1("This is Font 1!", QFont("Courier", 12));
  QLabel label2("This is Font 2!", QFont("Verdana", 18));

  label1.show();
  label2.show();

  // Swap fonts using std::swap
  std::swap(label1.font(), label2.font());

  // Update labels with the swapped fonts
  label1.setFont(label1.font());
  label2.setFont(label2.font());

  return app.exec();
}

This code utilizes std::swap to swap the entire QFont objects between the labels. Afterwards, it reapplies the fonts to the labels to ensure the changes take effect.

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1. Individual Property Assignment
   

This involves accessing and assigning individual font properties like family, size, weight, etc., between QFont objects. This method offers fine-grained control over specific font aspects you want to swap.

QFont font1("Arial", 12);
QFont font2("Times New Roman", 10);

// Swap font family
QString temp = font1.family();
font1.setFamily(font2.family());
font2.setFamily(temp);

// Similarly swap other properties like size, weight, etc.
int tempSize = font1.pointSize();
font1.setPointSize(font2.pointSize());
font2.setPointSize(tempSize);

1. Standard Template Library (STL) swap
   

The C++ STL offers a generic std::swap() function that can be used to swap the values of two variables of any type, including QFont. This approach is suitable if you're working with generic code and don't require modifying specific properties.

QFont font1("Arial", 12);
QFont font2("Times New Roman", 10);

std::swap(font1, font2);

// Apply the swapped fonts to your widgets
label1.setFont(font1);
label2.setFont(font2);

1. Creating New QFont Object
   

You can create a new QFont object with the desired properties and then assign it to your widget. This approach might be simpler for one-time swaps or when dealing with complex font configurations.

For example:

QFont newFont("Verdana", 14, QFont::Bold);

label1.setFont(newFont); // Assign the new font to label1

1. Using QSettings
   

If you want to store and load font settings persistently, consider using QSettings. You can convert your QFont object to a string representation using toString() and vice versa using the corresponding constructor.

// Save font settings
QSettings settings("MyCompany", "MyApp");
settings.setValue("font", font1.toString());

// Load font settings
QFont loadedFont = QFont(settings.value("font").toString());