Alternatives to QPlainTextEdit::zoomIn() for Text Zooming in Qt

QPlainTextEdit doesn't directly support zoomIn()

While QPlainTextEdit offers some methods like zoomIn() and zoomOut(), these functions might not directly control the text size as expected.

Zooming with Ctrl+Wheel

By default, Qt provides zooming functionality through the combination of Ctrl key pressed and mouse wheel scrolling. This behavior is likely what you'd expect from zoomIn().

Limited functionality of zoomIn() and zoomOut()

The documented purpose of QPlainTextEdit::zoomIn() and zoomOut() is actually for internal use by Qt. They might have some platform-specific effects, but their primary role isn't to control user-facing zoom.

Alternative Approaches for Zooming

Here are ways to achieve zooming in your application:

• Custom Zoom Controls
  Create buttons or menu options that trigger font size changes or other visual modifications to simulate zooming.
• Event handling
  Override the wheelEvent method in a class derived from QPlainTextEdit. Check for the Ctrl key being pressed and adjust the font size or other properties based on the wheel scroll direction.

---

Example 1: Overriding wheelEvent for zooming (C++)

This code demonstrates overriding the wheelEvent to zoom in/out based on Ctrl key and mouse wheel:

#include <QApplication>
#include <QPlainTextEdit>

class ZoomingTextEdit : public QPlainTextEdit {
  Q_OBJECT

public:
  ZoomingTextEdit(QWidget* parent = nullptr) : QPlainTextEdit(parent) {}

protected:
  void wheelEvent(QWheelEvent* event) override {
    if (event->modifiers() & Qt::ControlModifier) {
      int delta = event->delta();
      if (delta > 0) {
        zoomIn(2); // Adjust zoom factor as needed
      } else if (delta < 0) {
        zoomOut(2); // Adjust zoom factor as needed
      }
    } else {
      QPlainTextEdit::wheelEvent(event); // Pass through normal scrolling
    }
  }
};

int main(int argc, char* argv[]) {
  QApplication app(argc, argv);
  ZoomingTextEdit* editor = new ZoomingTextEdit;
  editor->show();
  return app.exec();
}

This code checks for the Ctrl key and adjusts the font size based on the wheel scroll direction. You can modify the zoomIn and zoomOut factors to control the zoom sensitivity.

Example 2: Simulating Zoom with Buttons (Python - PyQt)

This example uses buttons to trigger font size changes, simulating zooming:

from PyQt5.QtWidgets import QApplication, QPlainTextEdit, QVBoxLayout, QPushButton

class ZoomEditor(QWidget):
  def __init__(self):
    super().__init__()
    self.editor = QPlainTextEdit()
    self.zoom_in_btn = QPushButton("Zoom In")
    self.zoom_out_btn = QPushButton("Zoom Out")

    self.layout = QVBoxLayout()
    self.layout.addWidget(self.editor)
    self.layout.addWidget(self.zoom_in_btn)
    self.layout.addWidget(self.zoom_out_btn)
    self.setLayout(self.layout)

    self.zoom_in_btn.clicked.connect(self.increase_font)
    self.zoom_out_btn.clicked.connect(self.decrease_font)

  def increase_font(self):
    font = self.editor.font()
    font.setPointSize(font.pointSize() + 2)  # Adjust font size change
    self.editor.setFont(font)

  def decrease_font(self):
    font = self.editor.font()
    # Implement minimum font size check to avoid very small fonts
    if font.pointSize() > 6:  # Adjust minimum font size
      font.setPointSize(font.pointSize() - 2)
    self.editor.setFont(font)

if __name__ == "__main__":
  app = QApplication([])
  editor = ZoomEditor()
  editor.show()
  app.exec_()

This code creates buttons and connects them to functions that adjust the font size, simulating zooming in and out. Remember to implement a minimum font size check to avoid unreadable text.

---

1. • Override the wheelEvent method in a class derived from QPlainTextEdit.
   • Check for the Ctrl key being pressed and adjust the font size or other properties based on the wheel scroll direction.
   • This approach provides a familiar zooming experience for users (Ctrl+wheel).

2. Custom Zoom Controls
   

   • Create buttons or menu options that trigger font size changes or other visual modifications to simulate zooming.
   • You can also include zoom level indicators to provide feedback to the user.
   • This method offers more control over the zoom behavior and user interface.

3. QGraphicsView with QTextDocument
   

   • Instead of QPlainTextEdit, use QGraphicsView to display the text content.
   • Embed a QTextDocument within a QGraphicsItem and add it to the scene managed by QGraphicsView.
   • Utilize the scaling functionalities of QGraphicsView to zoom in and out on the entire document content.
   • This approach allows for more advanced zooming capabilities, including panning and scaling specific regions.

4. Third-party Libraries
   

   • Explore libraries like RichTextEdit or QtWebKit that might offer built-in zooming features for text editing.
   • These libraries can provide additional functionalities and a potentially simpler way to implement zooming.

• Explore existing functionalities
  Look into third-party libraries if they provide suitable zooming features.
• Advanced zooming with panning
  Consider QGraphicsView with QTextDocument.
• Customizable zooming UI
  Implement custom zoom controls.
• Simple zooming (Ctrl+wheel)
  Use event handling (wheelEvent).