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diff --git a/examples/corelib/serialization/streambookmarks/doc/src/qxmlstreambookmarks.qdoc b/examples/corelib/serialization/streambookmarks/doc/src/qxmlstreambookmarks.qdoc new file mode 100644 index 0000000000..8e32dd8d0b --- /dev/null +++ b/examples/corelib/serialization/streambookmarks/doc/src/qxmlstreambookmarks.qdoc @@ -0,0 +1,223 @@ +// Copyright (C) 2016 The Qt Company Ltd. +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only + +/*! + \example serialization/streambookmarks + \examplecategory {Data Processing & I/O} + \meta tag {network} + \title QXmlStream Bookmarks Example + \brief Demonstrates how to read and write XBEL files. + \ingroup xml-examples + + The QXmlStream Bookmarks example provides a viewer for XML Bookmark Exchange + Language (XBEL) files. It can read bookmarks using Qt's QXmlStreamReader and + write them back out again using QXmlStreamWriter. As this example aims to + show how to use these reader and writer types, it provides no means to open + a bookmark, add a new one, or merge two bookmark files, and only minimal + scope for editing bookmarks. None the less, it could surely be extended with + such features, if desired. + + \image screenshot.png + + \section1 XbelWriter Class Definition + + The \c XbelWriter class takes a \l{QTreeWidget}{tree widget} describing a + hierarchy of folders containing bookmarks. Its \c writeFile() provides the + means to write out this hierarchy, in XBEL format, to a given output device. + + Internally, it records the tree widget it was given and packages a private + instance of QXmlStreamWriter, which provides it with the means to stream + XML. It has an internal \c writeItem() to write each item in its tree. + + \snippet serialization/streambookmarks/xbelwriter.h 0 + + \section1 XbelWriter Class Implementation + + The \c XbelWriter constructor accepts the \a treeWidget it will describe. It + stores that and enables \l{QXmlStreamWriter}'s auto-formatting property. + This last splits the data into several lines, with indentation to indicate + the structure of the tree, which makes the XML output easier to read. + + \snippet serialization/streambookmarks/xbelwriter.cpp 0 + + The \c writeFile() function accepts a QIODevice object and directs its + QXmlStreamWriter member to write to this device, using \c setDevice(). This + function then writes the document type definition(DTD), the start element, + the version, and delegates writing of each of the \c{treeWidget}'s top-level + items to \c writeItem(). Finally, it closes the document and returns. + + \snippet serialization/streambookmarks/xbelwriter.cpp 1 + + The \c writeItem() function accepts a QTreeWidgetItem object and writes to + its XML stream a representation of the object, which depends on its \c + UserRole, which can be one of a \c{"folder"}, \c{"bookmark"}, + or \c{"separator"}. Within each folder, it calls itself recursively on each + child item, to recursively include a representation of each child within the + folder's XML element. + + \snippet serialization/streambookmarks/xbelwriter.cpp 2 + + \section1 XbelReader Class Definition + + The \c XbelReader takes a \l{QTreeWidget}{tree widget} to populate with + items describing a bookmark hierarchy. It supports reading XBEL data from a + QIODevice as a source of these items. If parsing of the XBEL data fails, it + can report what went wrong. + + Internally, it records the QTreeWidget that it will populate and packages an + instance of QXmlStreamReader, the companion class to QXmlStreamWriter, which + it will use to read XBEL data. + + \snippet serialization/streambookmarks/xbelreader.h 0 + + \section1 XbelReader Class Implementation + + Since the XBEL reader is only concerned with reading XML elements, it makes + extensive use of the \l{QXmlStreamReader::}{readNextStartElement()} + convenience function. + + The \c XbelReader constructor requires a QTreeWidget that it will populate. + It populates the tree widget's style with suitable icons: a folder icon that + changes form to indicate whether each folder as open or closed; and a + standard file icon for the individual bookmarks within those folders. + + \snippet serialization/streambookmarks/xbelreader.cpp 0 + + The \c read() function accepts a QIODevice. It directs its QXmlStreamReader + member to read content from that device. Note that the XML input must be + well-formed to be accepted by QXmlStreamReader. First it reads the outer + structure and verifies the content is an XBEL 1.0 file; if it is, \c read() + delegates the actual reading of content to the internal \c readXBEL(). + + Otherwise, the \l{QXmlStreamReader::}{raiseError()} function is used to + record an error message. The reader itself may also do the same if it + encounters errors in the input. When \c read() has finished, it returns + true if there were no errors. + + \snippet serialization/streambookmarks/xbelreader.cpp 1 + + If \c read() returns false, its caller can obtain a description of the + error, complete with line and column number within the stream, by calling + the \c errorString() function. + + \snippet serialization/streambookmarks/xbelreader.cpp 2 + + The \c readXBEL() function reads the name of a startElement and calls the + appropriate function to read it, depending on whether if its tag name + is \c{"folder"}, \c{"bookmark"} or \c{"separator"}. Any other elements + encountered are skipped. The function starts with a precondition, verifying + that the XML reader has just opened an \c{"xbel"} element. + + \snippet serialization/streambookmarks/xbelreader.cpp 3 + + The \c readBookmark() function creates a new editable item representing a + single bookmark. It records the XML \c{"href"} attribute of the current + element as second column text of the item and provisionally sets its first + column text to \c{"Unknown title"} before scanning the rest of the element + for a title element to over-ride that, skipping any unrecognized child + elements. + + \snippet serialization/streambookmarks/xbelreader.cpp 5 + + The \c readTitle() function reads a bookmark's title and records it as the + title (first column text) of the item for which it was called. + + \snippet serialization/streambookmarks/xbelreader.cpp 6 + + The \c readSeparator() function creates a separator and sets its flags. The + separator item's text is set to 30 centered dots. The rest of the element is + then skipped using \l{QXmlStreamReader::}{skipCurrentElement()}. + + \snippet serialization/streambookmarks/xbelreader.cpp 6 + + The \c readFolder() function creates an item and iterates the content of the + folder element, adding children to this item to represent the contents of + the folder element. The loop over folder content is similar in form to the + one in \c readXBEL(), save that it now accepts a title element to set the + title of the folder. + + \snippet serialization/streambookmarks/xbelreader.cpp 7 + + The \c createChildItem() helper function creates a new tree widget item + that's either a child of the given item or, if no parent item is given, a + direct child of the tree widget. It sets the new item's \c UserRole to the + tag name of the current XML element, matching how XbelWriter::writeFile() + uses that \c UserRole. + + \snippet serialization/streambookmarks/xbelreader.cpp 8 + + \section1 MainWindow Class Definition + + The \c MainWindow class is a subclass of QMainWindow, with a \c File menu + and a \c Help menu. + + \snippet serialization/streambookmarks/mainwindow.h 0 + + \section1 MainWindow Class Implementation + + The \c MainWindow constructor sets up its QTreeWidget object, \c treeWidget, + as its own central widget, with column headings for the title and location + of each book-mark. It configures a custom menu that enables the user to + perform actions on individual bookmarks within the tree widget. + + It invokes \c createMenus() to set up its own menus and their corresponding + actions. It sets its title, announces itself as ready and sets its size to a + reasonable proportion of the available screen space. + + \snippet serialization/streambookmarks/mainwindow.cpp 0 + + A custom menu, triggered when the user right-clicks on a bookmark, provides + for copying the bookmark as a link or directing a desktop browser to open + the URL it references. This menu is implemented (when relevant features are + enabled) by \c onCustomContextMenuRequested(). + + \snippet serialization/streambookmarks/mainwindow.cpp 1 + + The \c createMenus() function creates the \c fileMenu and \c helpMenu and + adds QAction objects to them, bound variously to the \c open(), \c saveAs() + and \c about() functions, along with QWidget::close() and + QApplication::aboutQt(). The connections are as shown below: + + \snippet serialization/streambookmarks/mainwindow.cpp 2 + + This creates the menu shown in the screenshots below: + + \table + \row + \li \inlineimage filemenu.png + \li \inlineimage helpmenu.png + \endtable + + The \c open() function, when triggered, offers the user a file dialog to use + to select a bookmarks file. If a file is selected, it is parsed using an \c + XBelReader to populate the \c treeWidget with bookmarks. If problems arise + with opening or parsing the file, a suitable warning message is displayed to + the user, including file name and error message. Otherwise, the bookmarks + read from the file are displayed and the window's status bar briefly reports + that the file has been loaded. + + \snippet serialization/streambookmarks/mainwindow.cpp 3 + + The \c saveAs() function displays a QFileDialog, prompting the user for a \c + fileName, to which to save a copy of the bookmarks data. Similar to the \c + open() function, this function also displays a warning message if the file + cannot be written to. + + \snippet serialization/streambookmarks/mainwindow.cpp 4 + + The \c about() function displays a QMessageBox with a brief description of + the example, or general information about Qt and the version of it in use. + + \snippet serialization/streambookmarks/mainwindow.cpp 5 + + \section1 \c{main()} Function + + The \c main() function instantiates \c MainWindow and invokes the \c show() + function to display it, then its \c open(), as this is most likely what the + user shall want to do first. + + \snippet serialization/streambookmarks/main.cpp 0 + + See the \l{https://pyxml.sourceforge.net/topics/xbel/} {XML Bookmark + Exchange Language Resource Page} for more information about XBEL files. +*/ |