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e1012. Retaining the Logical Style When Setting a New Paragraph Style

Logical styles are a collection of attributes that apply after the attributes of the paragraph style are applied. A common misconception of logical and paragraph styles is that they are independent. That is, setting a new logical style does not affect the current paragraph style and vice versa.

However, a logical style is nothing more than the parent of a paragraph style. If you replace the paragraph style, the logical style is replaced or removed as well. If you set a new logical style, the current parent of the current paragraph style (if any), is replaced with the new logical style.

In order to retain the logical style when setting a new paragraph style in non-replace mode, it is necessary to get the current logical style and restore it after setting the new paragraph style.

    JTextPane textPane = new JTextPane();
    
    // Set logical style
    Style style = textPane.addStyle(null, null);
    StyleConstants.setForeground(style, Color.red);
    textPane.setLogicalStyle(style);
    // paragraph is now red
    
    // Set paragraph style; removes logical style
    style = textPane.addStyle(null, null);
    StyleConstants.setUnderline(style, true);
    textPane.setParagraphAttributes(style, true);
    // paragraph is now underlined, not red
    
    // Set logical style; replaces paragraph style's parent
    style = textPane.addStyle(null, null);
    StyleConstants.setForeground(style, Color.red);
    textPane.setLogicalStyle(style);
    // paragraph is now red and underlined
    
    // Get logical style and restore it after new paragraph style
    Style logicalStyle = textPane.getLogicalStyle();
    style = textPane.addStyle(null, null);
    StyleConstants.setBold(style, true);
    textPane.setParagraphAttributes(style, true);
    textPane.setLogicalStyle(logicalStyle);
    // paragraph is now red and bold