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diff --git a/doc/src/frameworks-technologies/richtext.qdoc b/doc/src/frameworks-technologies/richtext.qdoc new file mode 100644 index 0000000000..7125b81b7f --- /dev/null +++ b/doc/src/frameworks-technologies/richtext.qdoc @@ -0,0 +1,1226 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at http://qt.nokia.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \group richtext-processing + \title Rich Text Processing APIs +*/ + +/*! + \page richtext.html + \title Rich Text Processing + \brief An overview of Qt's rich text processing, editing and display features. + + \ingroup frameworks-technologies + + \nextpage Rich Text Document Structure + + The Scribe framework provides a set of classes for reading and manipulating + structured rich text documents. Unlike previous rich text support in Qt, the + new classes are centered around the QTextDocument class rather than raw + textual information. This enables the developer to create and modify + structured rich text documents without having to prepare content in an + intermediate markup format. + + The information within a document can be accessed via two complementary + interfaces: A cursor-based interface is used for editing, and a read-only + hierarchical interface provides a high level overview of the document + structure. The main advantage of the cursor-based interface is that the + text can be edited using operations that mimic a user's interaction with + an editor, without losing the underlying structure of the document. The + read-only hierarchical interface is most useful when performing operations + such as searching and document export. + + This document is divided up into chapters for convenient reference: + + \list + \i \l{Rich Text Document Structure} outlines + the different kinds of elements in a QTextDocument, and describes how + they are arranged in a document structure. + \i \l{The QTextCursor Interface} explains how rich + text documents can be edited using the cursor-based interface. + \i \l{Document Layouts} briefly explains the role of document layouts. + \i \l{Common Rich Text Editing Tasks} examines some + common tasks that involve reading or manipulating rich text documents. + \i \l{Advanced Rich Text Processing} examines advanced rich text editing tasks. + \i \l{Supported HTML Subset} lists the HTML tags supported by QTextDocument. + \endlist + + \section1 Rich Text Processing APIs + + Qt provides an extensive collection of classes for parsing, rendering + manipulating and editing rich text. + + \annotatedlist richtext-processing +*/ + +/*! + \page richtext-structure.html + \contentspage richtext.html Contents + \previouspage Rich Text Processing + \nextpage The QTextCursor Interface + + \title Rich Text Document Structure + + \tableofcontents + + Text documents are represented by the QTextDocument class, which + contains information about the document's internal representation, its + structure, and keeps track of modifications to provide undo/redo + facilities. + + The structured representation of a text document presents its contents as + a hierarchy of text blocks, frames, tables, and other objects. These provide + a logical structure to the document and describe how their contents will be + displayed. Generally, frames and tables are used to group other + structures while text blocks contain the actual textual information. + + New elements are created and inserted into the document programmatically + \l{richtext-cursor.html}{with a QTextCursor} or by using an editor + widget, such as QTextEdit. Elements can be given a particular format when + they are created; otherwise they take the cursor's current format for the + element. + + \table + \row + \i \inlineimage richtext-document.png + \i \bold{Basic structure} + + The "top level" of a document might be populated in the way shown. + Each document always contains a root frame, and this always contains + at least one text block. + + For documents with some textual content, the root + frame usually contains a sequence of blocks and other elements. + + Sequences of frames and tables are always separated by text blocks in a + document, even if the text blocks contain no information. This ensures that + new elements can always be inserted between existing structures. + \endtable + + In this chapter, we look at each of the structural elements + used in a rich text document, outline their features and uses, and show + how to examine their contents. Document editing is described in + \l{richtext-cursor.html}{The QTextCursor Interface}. + + \section1 Rich Text Documents + + QTextDocument objects contain all the information required to construct + rich text documents. + Text documents can be accessed in two complementary ways: as a linear + buffer for editors to use, and as an object hierarchy that is useful to + layout engines. + In the hierarchical document model, objects generally correspond to + visual elements such as frames, tables, and lists. At a lower level, + these elements describe properties such as the text style and alignment. + The linear representation of the document is used for editing and + manipulation of the document's contents. + + Although QTextEdit makes it easy to display and edit rich text, documents + can also be used independently of any editor widget, for example: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 0 + + Alternatively, they can be extracted from an existing editor: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 1 + + This flexibility enables applications to handle multiple rich text + documents without the overhead of multiple editor widgets, or requiring + documents to be stored in some intermediate format. + + An empty document contains a root frame which itself contains a single + empty text block. Frames provide logical separation between parts of the document, but + also have properties that determine how they will appear when rendered. + A table is a specialized type of frame that consists of a number of + cells, arranged into rows and columns, each of which can contain + further structure and text. Tables provide management and layout + features that allow flexible configurations of cells to be created. + + Text blocks contain text fragments, each of which specifies text and + character format information. Textual properties are defined both at + the character level and at the block level. At the character level, + properties such as font family, text color, and font weight can be + specified. The block level properties control the higher level + appearance and behavior of the text, such as the direction of text + flow, alignment, and background color. + + The document structure is not manipulated directly. Editing is + performed through a cursor-based interface. + The \l{richtext-cursor.html}{text cursor interface} + automatically inserts new document elements into the root frame, and + ensures that it is padded with empty blocks where necessary. + + We obtain the root frame in the following manner: + + \snippet doc/src/snippets/textdocument-frames/xmlwriter.h 0 + \snippet doc/src/snippets/textdocument-frames/xmlwriter.cpp 0 + + When navigating the document structure, it is useful to begin at the + root frame because it provides access to the entire document structure. + + + \section1 Document Elements + + Rich text documents usually consist of common elements such as paragraphs, + frames, tables, and lists. These are represented in a QTextDocument + by the QTextBlock, QTextFrame, QTextTable, and QTextList classes. + Unlike the other elements in a document, images are represented by + specially formatted text fragments. This enables them to be placed + formatted inline with the surrounding text. + + The basic structural building blocks in documents are QTextBlock and + QTextFrame. Blocks themselves contain fragments of rich text + (QTextFragment), but these do not directly influence the high level + structure of a document. + + Elements which can group together other document elements are typically + subclasses of QTextObject, and fall into two categories: Elements that + group together text blocks are subclasses of QTextBlockGroup, and those + that group together frames and other elements are subclasses of QTextFrame. + + \section2 Text Blocks + + Text blocks are provided by the QTextBlock class. + + Text blocks group together fragments of text with different character formats, + and are used to represent paragraphs in the document. Each block + typically contains a number of text fragments with different styles. + Fragments are created when text is inserted into the document, and more + of them are added when the document is edited. The document splits, merges, + and removes fragments to efficiently represent the different styles + of text in the block. + + The fragments within a given block can be examined by using a + QTextBlock::iterator to traverse the block's internal structure: + + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 3 + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 5 + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 6 + + Blocks are also used to represent list items. As a result, blocks can + define their own character formats which contain information about + block-level decoration, such as the type of bullet points used for + list items. The formatting for the block itself is described by the + QTextBlockFormat class, and describes properties such as text alignment, + indentation, and background color. + + Although a given document may contain complex structures, once we have a + reference to a valid block in the document, we can navigate between each + of the text blocks in the order in which they were written: + + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 0 + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 1 + \snippet doc/src/snippets/textblock-fragments/xmlwriter.cpp 2 + + This method is useful for when you want to extract just the rich text from a + document because it ignores frames, tables, and other types of structure. + + QTextBlock provides comparison operators that make it easier to manipulate + blocks: \l{QTextBlock::operator==()}{operator==()} and + \l{QTextBlock::operator!=()}{operator!=()} are used to test whether two + blocks are the same, and \l{QTextBlock::operator<()}{operator<()} is used + to determine which one occurs first in a document. + + \section2 Frames + + Frames are provided by the QTextFrame class. + + Text frames group together blocks of text and child frames, creating + document structures that are larger than paragraphs. The format of a frame + specifies how it is rendered and positioned on the page. Frames are + either inserted into the text flow, or they float on the left or right + hand side of the page. + Each document contains a root frame that contains all the other document + elements. As a result, all frames except the root frame have a parent + frame. + + Since text blocks are used to separate other document elements, each + frame will always contain at least one text block, and zero or more + child frames. We can inspect the contents of a frame by using a + QTextFrame::iterator to traverse the frame's child elements: + + \snippet doc/src/snippets/textdocument-frames/xmlwriter.cpp 1 + \snippet doc/src/snippets/textdocument-frames/xmlwriter.cpp 2 + + Note that the iterator selects both frames and blocks, so it is necessary + to check which it is referring to. This allows us to navigate the document + structure on a frame-by-frame basis yet still access text blocks if + required. Both the QTextBlock::iterator and QTextFrame::iterator classes + can be used in complementary ways to extract the required structure from + a document. + + \section2 Tables + + Tables are provided by the QTextTable class. + + Tables are collections of cells that are arranged in rows and columns. + Each table cell is a document element with its own character format, but it + can also contain other elements, such as frames and text blocks. Table cells + are automatically created when the table is constructed, or when extra rows + or columns are added. They can also be moved between tables. + + QTextTable is a subclass of QTextFrame, so tables are treated like frames + in the document structure. For each frame that we encounter in the + document, we can test whether it represents a table, and deal with it in a + different way: + + \snippet doc/src/snippets/textdocument-tables/xmlwriter.cpp 0 + \snippet doc/src/snippets/textdocument-tables/xmlwriter.cpp 1 + + The cells within an existing table can be examined by iterating through + the rows and columns. + + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 9 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 10 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 11 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 12 + + + \section2 Lists + + Lists are provided by the QTextList class. + + Lists are sequences of text blocks that are formatted in the usual way, but + which also provide the standard list decorations such as bullet points and + enumerated items. Lists can be nested, and will be indented if the list's + format specifies a non-zero indentation. + + We can refer to each list item by its index in the list: + + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 0 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 1 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 2 + + Since QTextList is a subclass of QTextBlockGroup, it does not group the + list items as child elements, but instead provides various functions for + managing them. This means that any text block we find when traversing a + document may actually be a list item. We can ensure that list items are + correctly identified by using the following code: + + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 3 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 4 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 5 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 6 + \snippet doc/src/snippets/textdocument-listitems/mainwindow.cpp 7 + + + \section2 Images + + Images in QTextDocument are represented by text fragments that reference + external images via the resource mechanism. Images are created using the + cursor interface, and can be modified later by changing the character + format of the image's text fragment: + + \snippet doc/src/snippets/textdocument-imageformat/main.cpp 0 + \snippet doc/src/snippets/textdocument-imageformat/main.cpp 1 + \snippet doc/src/snippets/textdocument-imageformat/main.cpp 2 + + The fragment that represents the image can be found by iterating over + the fragments in the text block that contains the image. +*/ + +/*! + \page richtext-cursor.html + \contentspage richtext.html Contents + \previouspage Rich Text Document Structure + \nextpage Document Layouts + + \title The QTextCursor Interface + + \tableofcontents + + Documents can be edited via the interface provided by the QTextCursor + class; cursors are either created using a constructor or obtained from + an editor widget. The cursor is used to perform editing operations that + correspond exactly to those the user is able to make themselves in an + editor. As a result, information about the document structure is also + available through the cursor, and this allows the structure to be + modified. The use of a cursor-oriented interface for editing makes the + process of writing a custom editor simpler for developers, since the + editing operations can be easily visualized. + + The QTextCursor class also maintains information about any text it + has selected in the document, again following a model that is + conceptually similar to the actions made by the user to select text + in an editor. + + Rich text documents can have multiple cursors + associated with them, and each of these contains information about their + position in the document and any selections that they may hold. This + cursor-based paradigm makes common operations, such as cutting and pasting + text, simple to implement programmatically, yet it also allows more complex + editing operations to be performed on the document. + + This chapter describes most of the common editing operations that you + will need to perform using a cursor, from basic insertion of text and + document elements to more complex manipulation of document structures. + + \section1 Cursor-Based Editing + + At the simplest level, text documents are made up of a string of characters, + marked up in some way to represent the block structure of the text within the + document. QTextCursor provides a cursor-based interface that allows the + contents of a QTextDocument to be manipulated at the character level. Since + the elements (blocks, frames, tables, etc.) are also encoded in the character + stream, the document structure can itself be changed by the cursor. + + The cursor keeps track of its location within its parent document, and can + report information about the surrounding structure, such as the enclosing + text block, frame, table, or list. The formats of the enclosing structures + can also be directly obtained through the cursor. + + \section2 Using a Cursor + + The main use of a cursor is to insert or modify text within a block. + We can use a text editor's cursor to do this: + + \snippet doc/src/snippets/textblock-formats/main.cpp 0 + + Alternatively, we can obtain a cursor directly from a document: + + \snippet doc/src/snippets/textdocument-images/main.cpp 0 + + The cursor is positioned at the start of the document so that we can write + into the first (empty) block in the document. + + \section2 Grouping Cursor Operations + + A series of editing operations can be packaged together so that they can + be replayed, or undone together in a single action. This is achieved by + using the \c beginEditBlock() and \c endEditBlock() functions in the + following way, as in the following example where we select the word that + contains the cursor: + + \snippet doc/src/snippets/textdocument-selections/mainwindow.cpp 0 + + If editing operations are not grouped, the document automatically records + the individual operations so that they can be undone later. Grouping + operations into larger packages can make editing more efficient both for + the user and for the application, but care has to be taken not to group too + many operations together as the user may want find-grained control over the + undo process. + + \section2 Multiple Cursors + + Multiple cursors can be used to simultaneously edit the same document, + although only one will be visible to the user in a QTextEdit widget. + The QTextDocument ensures that each cursor writes text correctly and + does not interfere with any of the others. + + \omit + \snippet doc/src/snippets/textdocument-cursors/main.cpp 0 + \snippet doc/src/snippets/textdocument-cursors/main.cpp 1 + \endomit + + \section1 Inserting Document Elements + + QTextCursor provides several functions that can be used to change the + structure of a rich text document. Generally, these functions allow + document elements to be created with relevant formatting information, + and they are inserted into the document at the cursor's position. + + The first group of functions insert block-level elements, and update the + cursor position, but they do not return the element that was inserted: + + \list + \i \l{QTextCursor::insertBlock()}{insertBlock()} inserts a new text block + (paragraph) into a document at the cursor's position, and moves the + cursor to the start of the new block. + \i \l{QTextCursor::insertFragment()}{insertFragment()} inserts an existing + text fragment into a document at the cursor's position. + \i \l{QTextCursor::insertImage()}{insertImage()} inserts an image into a + document at the cursor's position. + \i \l{QTextCursor::insertText()}{insertText()} inserts text into the + document at the cursor's position. + \endlist + + You can examine the contents of the element that was inserted through the + cursor interface. + + The second group of functions insert elements that provide structure to + the document, and return the structure that was inserted: + + \list + \i \l{QTextCursor::insertFrame()}{insertFrame()} inserts a frame into the + document \e after the cursor's current block, and moves the cursor to + the start of the empty block in the new frame. + \i \l{QTextCursor::insertList()}{insertList()} inserts a list into the + document at the cursor's position, and moves the cursor to the start + of the first item in the list. + \i \l{QTextCursor::insertTable()}{insertTable()} inserts a table into + the document \e after the cursor's current block, and moves the cursor + to the start of the block following the table. + \endlist + + These elements either contain or group together other elements in the + document. + + \section2 Text and Text Fragments + + Text can be inserted into the current block in the current character + format, or in a custom format that is specified with the text: + + \snippet doc/src/snippets/textdocument-charformats/main.cpp 0 + + Once the character format has been used with a cursor, that format becomes + the default format for any text inserted with that cursor until another + character format is specified. + + If a cursor is used to insert text without specifying a character format, + the text will be given the character format used at that position in the + document. + + \section2 Blocks + + Text blocks are inserted into the document with the + \l{QTextCursor::insertBlock()}{insertBlock()} function. + + \snippet doc/src/snippets/textblock-formats/main.cpp 1 + + The cursor is positioned at the start of the new block. + + \section2 Frames + + Frames are inserted into a document using the cursor, and will be placed + within the cursor's current frame \e after the current block. + The following code shows how a frame can be inserted between two text + blocks in a document's root frame. We begin by finding the cursor's + current frame: + + \snippet doc/src/snippets/textdocument-frames/mainwindow.cpp 0 + + We insert some text in this frame then set up a frame format for the + child frame: + + \snippet doc/src/snippets/textdocument-frames/mainwindow.cpp 1 + + The frame format will give the frame an external margin of 32 pixels, + internal padding of 8 pixels, and a border that is 4 pixels wide. + See the QTextFrameFormat documentation for more information about + frame formats. + + The frame is inserted into the document after the preceding text: + + \snippet doc/src/snippets/textdocument-frames/mainwindow.cpp 2 + + We add some text to the document immediately after we insert the frame. + Since the text cursor is positioned \e{inside the frame} when it is inserted + into the document, this text will also be inserted inside the frame. + + Finally, we position the cursor outside the frame by taking the last + available cursor position inside the frame we recorded earlier: + + \snippet doc/src/snippets/textdocument-frames/mainwindow.cpp 3 + + The text that we add last is inserted after the child frame in the + document. Since each frame is padded with text blocks, this ensures that + more elements can always be inserted with a cursor. + + \section2 Tables + + Tables are inserted into the document using the cursor, and will be + placed within the cursor's current frame \e after the current block: + + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 0 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 3 + + Tables can be created with a specific format that defines the overall + properties of the table, such as its alignment, background color, and + the cell spacing used. It can also determine the constraints on each + column, allowing each of them to have a fixed width, or resize according + to the available space. + + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 2 + + The columns in the table created above will each take up a certain + percentage of the available width. Note that the table format is + optional; if you insert a table without a format, some sensible + default values will be used for the table's properties. + + Since cells can contain other document elements, they too can be + formatted and styled as necessary. + + Text can be added to the table by navigating to each cell with the cursor + and inserting text. + + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 4 + + We can create a simple timetable by following this approach: + + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 5 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 6 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 7 + \snippet doc/src/snippets/textdocument-tables/mainwindow.cpp 8 + + \section2 Lists + + Lists of block elements can be automatically created and inserted into the + document at the current cursor position. Each list that is created in this + way requires a list format to be specified: + + \snippet doc/src/snippets/textdocument-lists/mainwindow.cpp 0 + + The above code first checks whether the cursor is within an existing list + and, if so, gives the list format for the new list a suitable level of + indentation. This allows nested lists to be created with increasing + levels of indentation. A more sophisticated implementation would also use + different kinds of symbol for the bullet points in each level of the list. + + \section2 Images + + Inline images are added to documents through the cursor in the usual manner. + Unlike many other elements, all of the image properties are specified by the + image's format. This means that a QTextImageFormat object has to be + created before an image can be inserted: + + \snippet doc/src/snippets/textdocument-images/main.cpp 1 + + The image name refers to an entry in the application's resource file. + The method used to derive this name is described in + \l{resources.html}{The Qt Resource System}. + + \section1 Examples + + Rich text is stored in text documents that can either be created by + importing HTML from an external source, or generated using a QTextCursor. + + \section2 Manipulating Rich Text + + The easiest way to use a rich text document is through + the QTextEdit class, providing an editable view onto a document. The code + below imports HTML into a document, and displays the document using a + text edit widget. + + \snippet doc/src/snippets/scribe-overview/main.cpp 1 + + You can retrieve the document from the text edit using the + document() function. The document can then be edited programmatically + using the QTextCursor class. This class is modeled after a screen + cursor, and editing operations follow the same semantics. The following + code changes the first line of the document to a bold font, leaving all + other font properties untouched. The editor will be automatically + updated to reflect the changes made to the underlying document data. + + \snippet doc/src/snippets/scribe-overview/main.cpp 0 + + Note that the cursor was moved from the start of the first line to the + end, but that it retained an anchor at the start of the line. This + demonstrates the cursor-based selection facilities of the + QTextCursor class. + + \section2 Generating a Calendar + + Rich text can be generated very quickly using the cursor-based + approach. The following example shows a simple calendar in a + QTextEdit widget with bold headers for the days of the week: + + \snippet doc/src/snippets/textdocument-blocks/mainwindow.cpp 0 + \codeline + \snippet doc/src/snippets/textdocument-blocks/mainwindow.cpp 1 + \snippet doc/src/snippets/textdocument-blocks/mainwindow.cpp 2 + \snippet doc/src/snippets/textdocument-blocks/mainwindow.cpp 3 + + The above example demonstrates how simple it is to quickly generate new + rich text documents using a minimum amount of code. Although we have + generated a crude fixed-pitch calendar to avoid quoting too much code, + Scribe provides much more sophisticated layout and formatting features. +*/ + +/*! + \page richtext-layouts.html + \contentspage richtext.html Contents + \previouspage The QTextCursor Interface + \nextpage Common Rich Text Editing Tasks + + \title Document Layouts + + \tableofcontents + + The layout of a document is only relevant when it is to be displayed on + a device, or when some information is requested that requires a visual + representation of the document. Until this occurs, the document does + not need to be formatted and prepared for a device. + + \section1 Overview + + Each document's layout is managed by a subclass of the + QAbstractTextDocumentLayout class. This class provides a common + interface for layout and rendering engines. The default rendering + behavior is currently implemented in a private class. This approach + makes it possible to create custom layouts, and provides the + mechanism used when preparing pages for printing or exporting to + Portable Document Format (PDF) files. + + \section1 Example - Shaped Text Layout + + Sometimes it is important to be able to format plain text within an + irregularly-shaped region, perhaps when rendering a custom widget, for + example. Scribe provides generic features, such as those provided by + the QTextLayout class, to help developers perform word-wrapping and + layout tasks without the need to create a document first. + + \img plaintext-layout.png + + Formatting and drawing a paragraph of plain text is straightforward. + The example below will lay out a paragraph of text, using a single + font, around the right hand edge of a circle. + + \snippet doc/src/snippets/plaintextlayout/window.cpp 0 + + We create a text layout, specifying the text string we want to display + and the font to use. We ensure that the text we supplied is formatted + correctly by obtaining text lines from the text format, and wrapping + the remaining text using the available space. The lines are positioned + as we move down the page. + + The formatted text can be drawn onto a paint device; in the above code, + the text is drawn directly onto a widget. + */ + + /*! + \page richtext-common-tasks.html + \contentspage richtext.html Contents + \previouspage Document Layouts + \nextpage Advanced Rich Text Processing + + \title Common Rich Text Editing Tasks + + \tableofcontents + + There are a number of tasks that are often performed by developers + when editing and processing text documents using Qt. These include the use + of display widgets such as QTextBrowser and QTextEdit, creation of + documents with QTextDocument, editing using a QTextCursor, and + exporting the document structure. + This document outlines some of the more common ways of using the rich + text classes to perform these tasks, showing convenient patterns that can + be reused in your own applications. + + \section1 Using QTextEdit + + A text editor widget can be constructed and used to display HTML in the + following way: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 2 + + By default, the text editor contains a document with a root frame, inside + which is an empty text block. This document can be obtained so that it can + be modified directly by the application: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 3 + + The text editor's cursor may also be used to edit a document: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 4 + + Although a document can be edited using many cursors at once, a QTextEdit + only displays a single cursor at a time. Therefore, if we want to update the + editor to display a particular cursor or its selection, we need to set the + editor's cursor after we have modified the document: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 5 + + \section1 Selecting Text + + Text is selected by moving the cursor using operations that are similar to + those performed by a user in a text editor. To select text between two + points in the document, we need to position the cursor at the first point + then move it using a special mode (\l{QTextCursor::MoveMode}) with a + move operation (\l{QTextCursor::MoveOperation}). + When we select the text, we leave the selection anchor at the old cursor + position just as the user might do by holding down the Shift key when + selecting text: + + \snippet doc/src/snippets/textdocument-selections/mainwindow.cpp 1 + + In the above code, a whole word is selected using this method. QTextCursor + provides a number of common move operations for selecting individual + characters, words, lines, and whole blocks. + + \section1 Finding Text + + QTextDocument provides a cursor-based interface for searching, making + it easy to find and modify text in the style of a text editor. The following + code finds all the instances of a particular word in a document, and changes + the color of each: + + \snippet doc/src/snippets/textdocument-find/main.cpp 0 + \snippet doc/src/snippets/textdocument-find/main.cpp 1 + + Note that the cursor does not have to be moved after each search and replace + operation; it is always positioned at the end of the word that was just + replaced. + + \section1 Printing Documents + + QTextEdit is designed for the display of large rich text documents that are + read on screen, rendering them in the same way as a web browser. As a result, + it does not automatically break the contents of the document into page-sized + pieces that are suitable for printing. + + QTextDocument provides a \l{QTextDocument::print()}{print()} function to + allow documents to be printed using the QPrinter class. The following code + shows how to prepare a document in a QTextEdit for printing with a QPrinter: + + \snippet doc/src/snippets/textdocument-printing/mainwindow.cpp 0 + + The document is obtained from the text editor, and a QPrinter is constructed + then configured using a QPrintDialog. If the user accepts the printer's + configuration then the document is formatted and printed using the + \l{QTextDocument::print()}{print()} function. +*/ + +/*! + \page richtext-advanced-processing.html + \contentspage richtext.html Contents + \previouspage Common Rich Text Editing Tasks + \nextpage Supported HTML Subset + + \title Advanced Rich Text Processing + + \section1 Handling Large Files + + Qt does not limit the size of files that are used for text + processing. In most cases, this will not present a problem. For + especially large files, however, you might experience that your + application will become unresponsive or that you will run out of + memory. The size of the files you can load depends on your + hardware and on Qt's and your own application's implementation. + + If you are faced with this problem, we recommend that you address the + following issues: + + \list + \o You should consider breaking up large paragraphs into smaller + ones as Qt handles small paragraphs better. You could also + insert line breaks at regular intervals, which will look the + same as one large paragraph in a QTextEdit. + \o You can reduce the amount of blocks in a QTextDocument with + \l{QTextDocument::}{maximumBlockCount()}. The document is only + as large as the number of blocks as far as QTextEdit is concerned. + \o When adding text to a text edit, it is an advantage to add it + in an edit block (see example below). The result is that the + text edit does not need to build the entire document structure at once. + \endlist + + We give an example of the latter technique from the list. We assume that + the text edit is visible. + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 6 + + \omit + Ideas for other sections: + + * Hiding QTextBlock elements. + * Changing the word wrapping mode in QTextEdit. Custom word wrapping? + \endomit +*/ + +/*! + \page richtext-html-subset.html + \title Supported HTML Subset + \brief Describes the support for HTML markup in text widgets. + + \contentspage richtext.html Contents + \previouspage Common Rich Text Editing Tasks + + Qt's text widgets are able to display rich text, specified using a subset of \l{HTML 4} + markup. Widgets that use QTextDocument, such as QLabel and QTextEdit, are able to display + rich text specified in this way. + + \tableofcontents + + \section1 Using HTML Markup in Text Widgets + + Widgets automatically detect HTML markup and display rich text accordingly. For example, + setting a label's \l{QLabel::}{text} property with the string \c{"<b>Hello</b> <i>Qt!</i>"} + will result in the label displaying text like this: \bold{Hello} \e{Qt!} + + When HTML markup is used for text, Qt follows the rules defined by the \l{HTML 4} + specification. This includes default properties for text layout, such as the + direction of the text flow (left-to-right) which can be changed by applying the + \l{#Block Attributes}{\c dir} attribute to blocks of text. + + \section1 Supported Tags + + The following table lists the HTML tags supported by Qt's + \l{Rich Text Processing}{rich text} engine: + + \table + \header \o Tag + \o Description + \o Comment + \row \o \c a + \o Anchor or link + \o Supports the \c href and \c name attributes. + \row \o \c address + \o Address + \o + \row \o \c b + \o Bold + \o + \row \o \c big + \o Larger font + \o + \row \o \c blockquote + \o Indented paragraph + \o + \row \o \c body + \o Document body + \o Supports the \c bgcolor attribute, which + can be a Qt \l{QColor::setNamedColor()}{color name} + or a \c #RRGGBB color specification. + \row \o \c br + \o Line break + \o + \row \o \c center + \o Centered paragraph + \o + \row \o \c cite + \o Inline citation + \o Same as \c i. + \row \o \c code + \o Code + \o Same as \c tt. + \row \o \c dd + \o Definition data + \o + \row \o \c dfn + \o Definition + \o Same as \c i. + \row \o \c div + \o Document division + \o Supports the standard \l{block attributes}. + \row \o \c dl + \o Definition list + \o Supports the standard \l{block attributes}. + \row \o \c dt + \o Definition term + \o Supports the standard \l{block attributes}. + \row \o \c em + \o Emphasized + \o Same as \c i. + \row \o \c font + \o Font size, family, and/or color + \o Supports the following attributes: + \c size, \c face, and \c color (Qt + \l{QColor::setNamedColor()}{color names} or + \c #RRGGBB). + \row \o \c h1 + \o Level 1 heading + \o Supports the standard \l{block attributes}. + \row \o \c h2 + \o Level 2 heading + \o Supports the standard \l{block attributes}. + \row \o \c h3 + \o Level 3 heading + \o Supports the standard \l{block attributes}. + \row \o \c h4 + \o Level 4 heading + \o Supports the standard \l{block attributes}. + \row \o \c h5 + \o Level 5 heading + \o Supports the standard \l{block attributes}. + \row \o \c h6 + \o Level 6 heading + \o Supports the standard \l{block attributes}. + \row \o \c head + \o Document header + \o + \row \o \c hr + \o Horizontal line + \o Supports the \c width attribute, which can + be specified as an absolute or relative (\c %) value. + \row \o \c html + \o HTML document + \o + \row \o \c i + \o Italic + \o + \row \o \c img + \o Image + \o Supports the \c src, \c source + (for Qt 3 compatibility), \c width, and \c height + attributes. + \row \o \c kbd + \o User-entered text + \o + \row \o \c meta + \o Meta-information + \o If a text encoding is specified using the \c{meta} tag, + it is picked up by Qt::codecForHtml(). + Likewise, if an encoding is specified to + QTextDocument::toHtml(), the encoding is stored using + a \c meta tag, for example: + + \snippet doc/src/snippets/code/doc_src_richtext.qdoc 7 + + \row \o \c li + \o List item + \o + \row \o \c nobr + \o Non-breakable text + \o + \row \o \c ol + \o Ordered list + \o Supports the standard \l{list attributes}. + \row \o \c p + \o Paragraph + \o Left-aligned by default. Supports the standard + \l{block attributes}. + \row \o \c pre + \o Preformated text + \o + \row \o \c qt + \o Qt rich-text document + \o Synonym for \c html. Provided for compatibility with + earlier versions of Qt. + \row \o \c s + \o Strikethrough + \o + \row \o \c samp + \o Sample code + \o Same as \c tt. + \row \o \c small + \o Small font + \o + \row \o \c span + \o Grouped elements + \o + \row \o \c strong + \o Strong + \o Same as \c b. + \row \o \c sub + \o Subscript + \o + \row \o \c sup + \o Superscript + \o + \row \o \c table + \o Table + \o Supports the following attributes: \c border, + \c bgcolor (Qt \l{QColor::setNamedColor()}{color names} + or \c #RRGGBB), \c cellspacing, \c cellpadding, + \c width (absolute or relative), and \c height. + \row \o \c tbody + \o Table body + \o Does nothing. + \row \o \c td + \o Table data cell + \o Supports the standard \l{table cell attributes}. + \row \o \c tfoot + \o Table footer + \o Does nothing. + \row \o \c th + \o Table header cell + \o Supports the standard \l{table cell attributes}. + \row \o \c thead + \o Table header + \o If the \c thead tag is specified, it is used when printing tables + that span multiple pages. + \row \o \c title + \o Document title + \o The value specified using the \c + title tag is available through + QTextDocument::metaInformation(). + \row \o \c tr + \o Table row + \o Supports the \c bgcolor attribute, which + can be a Qt \l{QColor::setNamedColor()}{color name} + or a \c #RRGGBB color specification. + \row \o \c tt + \o Typewrite font + \o + \row \o \c u + \o Underlined + \o + \row \o \c ul + \o Unordered list + \o Supports the standard \l{list attributes}. + \row \o \c var + \o Variable + \o Same as \c i. + \endtable + + \section1 Block Attributes + + The following attributes are supported by the \c div, \c dl, \c + dt, \c h1, \c h2, \c h3, \c h4, \c h5, \c h6, \c p tags: + + \list + \o \c align (\c left, \c right, \c center, \c justify) + \o \c dir (\c ltr, \c rtl) + \endlist + + \section1 List Attributes + + The following attribute is supported by the \c ol and \c ul tags: + + \list + \o \c type (\c 1, \c a, \c A, \c square, \c disc, \c circle) + \endlist + + \section1 Table Cell Attributes + + The following attributes are supported by the \c td and \c th + tags: + + \list + \o \c width (absolute, relative, or no-value) + \o \c bgcolor (Qt \l{QColor::setNamedColor()}{color names} or \c #RRGGBB) + \o \c colspan + \o \c rowspan + \o \c align (\c left, \c right, \c center, \c justify) + \o \c valign (\c top, \c middle, \c bottom) + \endlist + + \section1 CSS Properties + The following table lists the CSS properties supported by Qt's + \l{Rich Text Processing}{rich text} engine: + + \table + \header \o Property + \o Values + \o Description + \row + \o \c background-color + \o <color> + \o Background color for elements + \row + \o \c background-image + \o <uri> + \o Background image for elements + \row \o \c color + \o <color> + \o Text foreground color + \row \o \c font-family + \o <family name> + \o Font family name + \row \o \c font-size + \o [ small | medium | large | x-large | xx-large ] | <size>pt | <size>px + \o Font size relative to the document font, or specified in points or pixels + \row \o \c font-style + \o [ normal | italic | oblique ] + \o + \row \o \c font-weight + \o [ normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 ] + \o Specifies the font weight used for text, where \c normal and \c bold + are mapped to the corresponding QFont weights. Numeric values are + 8 times the equivalent QFont weight values. + \row \o \c text-decoration + \o none | [ underline || overline || line-through ] + \o Additional text effects + \row \o \c font + \o [ [ <'font-style'> || <'font-weight'> ]? <'font-size'> <'font-family'> ] + \o Font shorthand property + \row \o \c text-indent + \o <length>px + \o First line text indentation in pixels + \row \o \c white-space + \o normal | pre | nowrap | pre-wrap + \o Declares how whitespace in HTML is handled. + \row \o \c margin-top + \o <length>px + \o Top paragraph margin in pixels + \row \o \c margin-bottom + \o <length>px + \o Bottom paragraph margin in pixels + \row \o \c margin-left + \o <length>px + \o Left paragraph margin in pixels + \row \o \c margin-right + \o <length>px + \o Right paragraph margin in pixels + \row \o \c padding-top + \o <length>px + \o Top table cell padding in pixels + \row \o \c padding-bottom + \o <length>px + \o Bottom table cell padding in pixels + \row \o \c padding-left + \o <length>px + \o Left table cell padding in pixels + \row \o \c padding-right + \o <length>px + \o Right table cell padding in pixels + \row \o \c padding + \o <length>px + \o Shorthand for setting all the padding properties at once. + \row \o \c vertical-align + \o baseline | sub | super | middle | top | bottom + \o Vertical text alignment. For vertical alignment in text table cells only middle, top, and bottom apply. + \row \o \c border-color + \o <color> + \o Border color for text tables. + \row \o \c border-style + \o none | dotted | dashed | dot-dash | dot-dot-dash | solid | double | groove | ridge | inset | outset + \o Border style for text tables. + \row \o \c background + \o [ <'background-color'> || <'background-image'> ] + \o Background shorthand property + \row \o \c page-break-before + \o [ auto | always ] + \o Make it possible to enforce a page break before the paragraph/table + \row \o \c page-break-after + \o [ auto | always ] + \o Make it possible to enforce a page break after the paragraph/table + \row \o float + \o [ left | right | none ] + \o Specifies where an image or a text will be placed in another element. Note that the \c float property is + only supported for tables and images. + \row \o \c text-transform + \o [ uppercase | lowercase ] + \o Select the transformation that will be performed on the text prior to displaying it. + \row \o \c font-variant + \o small-caps + \o Perform the smallcaps transformation on the text prior to displaying it. + \row \o \c word-spacing + \o <width>px + \o Specifies an alternate spacing between each word. + \endtable + + \section1 Supported CSS Selectors + + All CSS 2.1 selector classes are supported except pseudo-class selectors such + as \c{:first-child}, \c{:visited} and \c{:hover}. + +*/ |