Beyond Block Formatting: Exploring Alternatives to QTextCursor::blockCharFormat() in Qt

What it is

• blockCharFormat() is a member function of QTextCursor that retrieves the character formatting information applied to the entire block (paragraph) where the cursor is currently positioned.
• QTextCursor is a class in Qt that represents the position and selection within a text document.

What it does

• This format information is typically applied uniformly to all characters within the block.
• It returns a QTextCharFormat object, which encapsulates various formatting properties like font family, size, weight, color, background color, underline style, etc.

When to use it

• You might use blockCharFormat() in several scenarios:
  • To inspect the existing formatting of a block before modifying it.
  • To apply the same formatting to multiple blocks by copying the format retrieved from one block and setting it on others.
  • To conditionally apply different formatting based on the retrieved format properties (e.g., only make a change if the font family is a specific one).

Example

#include <QApplication>
#include <QTextEdit>

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

    QTextEdit *textEdit = new QTextEdit;

    // Get the cursor
    QTextCursor cursor = textEdit->textCursor();

    // Check if the cursor is within a block
    if (cursor.hasSelection() || !cursor.atBlockStart()) {
        // Retrieve the character format of the block
        QTextCharFormat blockFormat = cursor.blockCharFormat();

        // Access and modify specific formatting properties (e.g., font size)
        blockFormat.setFontPointSize(16);

        // Set the modified format back to the block
        cursor.setBlockCharFormat(blockFormat);
    }

    textEdit->show();

    return app.exec();
}

1. Includes and application setup
   Standard Qt includes and application creation.
2. Create a QTextEdit
   This is the text editing widget where the formatting will be applied.
3. Get the cursor
   Retrieve the current text cursor using textCursor().
4. Check cursor position
   Ensure the cursor is within a block (not in the middle of a line) before proceeding.
5. Retrieve block format
   Call blockCharFormat() to get the formatting information for the current block.
6. Modify format
   Here, the font size is changed to 16 using setFontPointSize(). You can modify other properties as needed.
7. Set block format
   Apply the modified format back to the block using setBlockCharFormat().
8. Show the text edit
   Display the QTextEdit for the user to see the applied formatting.

• Explore other methods in QTextCursor and QTextCharFormat for various formatting options and selection handling.
• If you need to modify formatting within a specific range of characters within the block, use QTextCursor::setCharFormat() instead.

---

Copying formatting from one block to another

#include <QApplication>
#include <QTextEdit>

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

    QTextEdit *textEdit = new QTextEdit;

    // Get the cursor positions for the source and target blocks
    QTextCursor sourceCursor = textEdit->textCursor();
    sourceCursor.movePosition(QTextCursor::StartOfBlock); // Ensure at block start
    QTextCursor targetCursor = textEdit->textCursor();
    targetCursor.movePosition(QTextCursor::StartOfLine, QTextCursor::MoveAnchor, 2); // Move down 2 lines

    // Check if both cursors are within blocks
    if (sourceCursor.hasSelection() || !sourceCursor.atBlockStart() ||
        targetCursor.hasSelection() || !targetCursor.atBlockStart()) {
        // Get the block format from the source block
        QTextCharFormat sourceFormat = sourceCursor.blockCharFormat();

        // Set the format on the target block
        targetCursor.setBlockCharFormat(sourceFormat);
    }

    textEdit->show();

    return app.exec();
}

This code copies the formatting from the block where the sourceCursor is positioned to the block where the targetCursor is positioned.

Conditionally applying formatting based on existing format

#include <QApplication>
#include <QTextEdit>

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

    QTextEdit *textEdit = new QTextEdit;

    QTextCursor cursor = textEdit->textCursor();

    if (cursor.hasSelection() || !cursor.atBlockStart()) {
        // Get the block format
        QTextCharFormat blockFormat = cursor.blockCharFormat();

        // Check if the font family is "Courier"
        if (blockFormat.font().family() == "Courier") {
            // Change font size to 14 if it's Courier
            blockFormat.setFontPointSize(14);
        } else {
            // Set a different format for non-Courier fonts (e.g., bold)
            blockFormat.setFontWeight(QFont::Bold);
        }

        // Apply the modified format back to the block
        cursor.setBlockCharFormat(blockFormat);
    }

    textEdit->show();

    return app.exec();
}

This code checks the font family of the block where the cursor is positioned. If it's "Courier", the font size is changed to 14. Otherwise, the font is made bold.

---

Using `QTextDocument::findBlockFormats() directly

• This approach offers more granular control if you need to inspect or modify individual character formats within the block.
• It returns a QList<QTextCharFormat> containing the formats for each character or range of characters within the block.
• This method allows you to find all character formats applied within a specific block.

#include <QApplication>
#include <QTextEdit>

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

    QTextEdit *textEdit = new QTextEdit;

    QTextCursor cursor = textEdit->textCursor();

    if (cursor.hasSelection() || !cursor.atBlockStart()) {
        // Get the current block
        QTextBlock block = cursor.block();

        // Find all character formats within the block
        QList<QTextCharFormat> formats = block.document()->findBlockFormats(block.position());

        // Access and modify individual formats within the list (if needed)
    }

    textEdit->show();

    return app.exec();
}

Iterating through the block using QTextBlockIterator

• This method provides the most fine-grained control over character formatting within the block.
• For each character, you can access its corresponding QTextCharFormat using fragment().charFormat().
• You can then iterate through each character or range of characters within the block.
• This approach involves creating a QTextBlockIterator for the block of interest.

#include <QApplication>
#include <QTextEdit>

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

    QTextEdit *textEdit = new QTextEdit;

    QTextCursor cursor = textEdit->textCursor();

    if (cursor.hasSelection() || !cursor.atBlockStart()) {
        // Get the current block
        QTextBlock block = cursor.block();

        // Create an iterator for the block
        QTextBlockIterator it(block);

        // Iterate through each fragment (character or range)
        while (it.hasNext()) {
            QTextFragment fragment = it.next();
            QTextCharFormat format = fragment.charFormat();

            // Access and modify the format for each fragment (if needed)
        }
    }

    textEdit->show();

    return app.exec();
}

• If you need to examine or modify individual character formats within the block, consider QTextDocument::findBlockFormats() or QTextBlockIterator depending on the level of granularity required.
• If you simply need to access the overall formatting applied uniformly to the entire block, QTextCursor::blockCharFormat() is the most efficient option.