okular/core/textpage.h

/***************************************************************************
 *   Copyright (C) 2005 by Piotr Szymanski <niedakh@gmail.com>             *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 ***************************************************************************/

#ifndef _OKULAR_TEXTPAGE_H_
#define _OKULAR_TEXTPAGE_H_

#include <QList>
#include <QString>

#include "okularcore_export.h"
#include "global.h"

class QTransform;

namespace Okular {

class NormalizedPoint;
class NormalizedRect;
class Page;
class PagePrivate;
class TextPagePrivate;
class TextSelection;
class RegularAreaRect;

/*! @class TextEntity
 * @short Represents a piece of text on a TextPage, containing its textual representation and its bounding box.
 *
 * To enable searching and text selection, a generator can give information about the textual
 * content of a Page using a TextPage.
 * A TextPage is created using TextEntity objects.
 * A TextEntity can represent a single character/glyph, a word, a line, or even the whole page.
 *
 * Ideally, every single glyph is represented by its own TextEntity.
 * If the textual representation of a graphical glyph contains more than one character,
 * the TextEntity must contain the whole string which represents the glyph.
 *
 * When the Generator has created the TextPage, and it is added to a Page,
 * the text entities are reordered to words, lines, and paragraphs, to optimize search and text selection.
 * This way, the Generator does not need to care about the logical order of lines or paragraphs.
 *
 * @par Text Selection/Highlighting
 * A TextEntity is the smallest piece of text, which the user can select, or which can be highlighted.
 * That is, if the TextEntity represents a word, only the whole word can be selected.
 * It would not be possible to select a single glyph of the word, because its bounding box is not known.
 *
 * @see TextPage, Generator
 */
class OKULARCORE_EXPORT TextEntity
{
    public:
        typedef QList<TextEntity*> List;

        /**
         * Creates a new text entity with the given @p text and the
         * given @p area.
         */
        TextEntity( const QString &text, NormalizedRect *area );

        /**
         * Destroys the text entity.
         */
        ~TextEntity();

        /**
         * Returns the text of the text entity.
         */
        QString text() const;

        /**
         * Returns the bounding area of the text entity.
         */
        NormalizedRect* area() const;

        /**
         * Returns the transformed area of the text entity.
         */
        NormalizedRect transformedArea(const QTransform &matrix) const;

    private:
        QString m_text;
        NormalizedRect* m_area;

        class Private;
        const Private *d;

        Q_DISABLE_COPY( TextEntity )
};

/**
 * @short Represents the textual information of a Page. Makes search and text selection possible.
 *
 * A Generator with text support should add a TextPage to every Page.
 * For every piece of text, a TextEntity is added, holding the string representation and the bounding box.
 *
 * Ideally, every TextEntity describes only one glyph.
 * A "glyph" is one character in the graphical representation, but the textual representation may consist of multiple characters (like diacritic modifiers).
 *
 * When the TextPage is added to the Page, the TextEntitys are restructured to optimize text selection.
 *
 * @see TextEntity
 */
class OKULARCORE_EXPORT TextPage
{
    /// @cond PRIVATE
    friend class Page;
    friend class PagePrivate;
    /// @endcond

    public:
        /**
         * Defines the behaviour of adding characters to text() result
         * @since 0.10 (KDE 4.4)
         */
        enum TextAreaInclusionBehaviour
        {
            AnyPixelTextAreaInclusionBehaviour,      ///< A character is included into text() result if any pixel of his bounding box is in the given area
            CentralPixelTextAreaInclusionBehaviour  ///< A character is included into text() result if the central pixel of his bounding box is in the given area
        };

        /**
         * Creates a new text page.
         */
        TextPage();

        /**
         * Creates a new text page with the given @p words.
         */
        explicit TextPage( const TextEntity::List &words );

        /**
         * Destroys the text page.
         */
        ~TextPage();

        /**
         * Appends the given @p text with the given @p area as new
         * @ref TextEntity to the page.
         */
        void append( const QString &text, NormalizedRect *area );

        /**
         * Returns the bounding rect of the text which matches the following criteria
         * or 0 if the search is not successful.
         *
         * @param searchID An unique id for this search.
         * @param query The search text.
         * @param direction The direction of the search (@ref SearchDirection)
         * @param caseSensitivity If Qt::CaseSensitive, the search is case sensitive; otherwise
         *                        the search is case insensitive.
         * @param area If null the search starts at the beginning of the page, otherwise
         *                 right/below the coordinates of the given rect.
         */
        RegularAreaRect* findText( int searchID, const QString &query, SearchDirection direction,
                                   Qt::CaseSensitivity caseSensitivity, const RegularAreaRect *area );

        /**
         * Text extraction function. Looks for text in the given @p area.
         *
         * @return
         * - If @p area points to a valid null area, a null string.
         * - If @p area is nullptr, the whole page text as a single string.
         * - Otherwise, the text which is included by @p area, as a single string.
         * Uses AnyPixelTextAreaInclusionBehaviour
         */
        QString text( const RegularAreaRect *area = nullptr ) const;

        /**
         * Text extraction function. Looks for text in the given @p area.
         *
         * @return
         * - If @p area points to a valid null area, a null string.
         * - If @p area is nullptr, the whole page text as a single string.
         * - Otherwise, the text which is included by @p area, as a single string.
         * @since 0.10 (KDE 4.4)
         */
        QString text( const RegularAreaRect * area, TextAreaInclusionBehaviour b ) const;

        /**
         * Text entity extraction function. Similar to text() but returns
         * the words including their bounding rectangles. Note that
         * ownership of the contents of the returned list belongs to the
         * caller.
         * @since 0.14 (KDE 4.8)
         */
        TextEntity::List words( const RegularAreaRect * area, TextAreaInclusionBehaviour b ) const;

        /**
         * Returns the area and text of the word at the given point
         * Note that ownership of the returned area belongs to the caller.
         * @since 0.15 (KDE 4.9)
         */
        RegularAreaRect * wordAt( const NormalizedPoint &p, QString *word = nullptr ) const;

        /**
         * Returns the rectangular area of the given @p selection.
         */
        RegularAreaRect *textArea( TextSelection *selection ) const;

    private:
        TextPagePrivate* const d;

        Q_DISABLE_COPY( TextPage )
};

}

#endif