Document text flow (first part)

PdfForQtLib/sources/pdfdocumenttextflow.h

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+//    Copyright (C) 2020 Jakub Melka
+//
+//    This file is part of PdfForQt.
+//
+//    PdfForQt is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Lesser General Public License as published by
+//    the Free Software Foundation, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    PdfForQt is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Lesser General Public License for more details.
+//
+//    You should have received a copy of the GNU Lesser General Public License
+//    along with PDFForQt.  If not, see <https://www.gnu.org/licenses/>.
+
+#ifndef PDFDOCUMENTTEXTFLOW_H
+#define PDFDOCUMENTTEXTFLOW_H
+
+#include "pdfglobal.h"
+#include "pdfexception.h"
+
+namespace pdf
+{
+class PDFDocument;
+
+/// Text flow extracted from document. Text flow can be created \p PDFDocumentTextFlowFactory.
+/// Flow can contain various items, not just text ones. Also, some manipulation functions
+/// are available, they can modify text flow by various content.
+class PDFFORQTLIBSHARED_EXPORT PDFDocumentTextFlow
+{
+public:
+
+    enum Flag
+    {
+        None                                = 0x0000,   ///< No text flag
+        Text                                = 0x0001,   ///< Ordinary text
+        PageStart                           = 0x0002,   ///< Page start marker
+        PageEnd                             = 0x0004,   ///< Page end marker
+        StructureTitle                      = 0x0008,   ///< Structure tree item title
+        StructureLanguage                   = 0x0010,   ///< Structure tree item language
+        StructureAlternativeDescription     = 0x0020,   ///< Structure tree item alternative description
+        StructureExpandedForm               = 0x0040,   ///< Structure tree item expanded form of text
+        StructureActualText                 = 0x0080,   ///< Structure tree item actual text
+        StructurePhoneme                    = 0x0100,   ///< Structure tree item  phoneme
+        StructureItemStart                  = 0x0200,   ///< Start of structure tree item
+        StructureItemEnd                    = 0x0400,   ///< End of structure tree item
+        StructureEmpty                      = 0x0800,   ///< Structure tree item doesn't contain any text
+    };
+    Q_DECLARE_FLAGS(Flags, Flag)
+
+    struct Item
+    {
+        Flags flags = None;
+        PDFInteger pageIndex = 0;
+        QString text;
+    };
+    using Items = std::vector<Item>;
+
+    explicit PDFDocumentTextFlow() = default;
+    explicit PDFDocumentTextFlow(Items&& items) :
+        m_items(qMove(items))
+    {
+
+    }
+
+    const Items& getItems() const { return m_items; }
+
+private:
+    Items m_items;
+};
+
+/// This factory creates text flow for whole document
+class PDFDocumentTextFlowFactory
+{
+public:
+    explicit PDFDocumentTextFlowFactory() = default;
+
+    enum class Algorithm
+    {
+        Auto,       ///< Determine best text layout algorithm automatically
+        Layout,     ///< Use text layout recognition using docstrum algorithm
+        Content,    ///< Use content-stream text layout recognition (usually unreliable), but fast
+        Structure,  ///< Use structure oriented text layout recognition (requires tagged document)
+    };
+
+    /// Performs document text flow analysis using given algorithm. Text flow
+    /// can be performed only for given subset of pages, if required.
+    /// \param document Document
+    /// \param pageIndices Analyzed page indices
+    /// \param algorithm Algorithm
+    PDFDocumentTextFlow create(const PDFDocument* document,
+                               const std::vector<PDFInteger>& pageIndices,
+                               Algorithm algorithm);
+
+    /// Has some error/warning occured during text layout creation?
+    bool hasError() const { return !m_errors.isEmpty(); }
+
+    /// Returns a list of errors/warnings
+    const QList<PDFRenderError>& getErrors() const { return m_errors; }
+
+private:
+    QList<PDFRenderError> m_errors;
+};
+
+}   // namespace pdf
+
+#endif // PDFDOCUMENTTEXTFLOW_H